Program Listings

Session Chair: Shaun Clarke, University of Michigan, United States; Adam Conway, Lawrence Livermore National Laboratory, United States

Data acquisition systems for Time Projection Chambers (TPC) are notoriously complex. In TPCs a physics event is represented by a 3-dimensional image of ionization tracks. A larger number of pixels will provide a higher quality image. A quick estimate illustrates the issue: for a 10,000 channel detector recording 500 samples (or time buckets) at a rate of 1,000 events per second, the amount of data bandwidth is 60 Gigabits per second, assuming each datum is represented it as a 12 bit sample. Clearly some kind of data pre-processing and reduction at the front-end level is necessary to attain a more reasonable throughput that can be processed and stored by the back end. This is the role of CoBo. CoBo is a digital board developed (design, layout, and firmware) at NSCL for GET (General Electronics for Time Projection Chambers). It conforms to MicroTCA.0 AMC standard. The main objectives of CoBo are the following: (a) Reduce the detectorï¿½s high-bandwidth raw data to manageable packet-like data (1Gb/s maximum) for offline processing and storage. (b) Implement Time stamping in order to correlate events in the chamber. (c) Relay and integrate multiplicity and hit pattern information to a custom MicroTCA Carrier Hub (MCH2). (d) Perform the control configuration of the analog front end boards and Application Specific Integrated Circuits (ASICs) as well as digital front end i.e. CoBo. Furthermore, the firmware is designed to utilize and saturate the maximum possible bandwidth of the on-board DDR2 (double-data-rate) memory at 1500 MB/s. Additionally, using the PowerPC CPU direct memory access on the 1000Base-X Ethernet peripheral along with TCP/IP as a communication protocol, it is possible to transfer processed data up to 800Mbps to remote CPU farm and storage.

We report the upgrade of data acquisition (DAQ) system for user experiments at the X-ray Free-Electron Laser (XFEL) facility, SACLA, in the SPring-8 site. The SACLA is designed to operate up to five beamlines simultaneously. As of 2014, SACLA provides only one beamline for user experiments. The standardized framework of DAQ has been provided to the user experiments of various setups. The experiments produce TOF waveforms or 2-dimensional images of X-ray diffraction pattern, of which the data size ranges up to 12 MB for each XFEL beam pulse. It consists of the trigger system, data-handling servers, high-speed storage, archive storage, and the relational database. So far all these resources are employed by the single set of DAQ system to handle one experiment at a time. In 2014, another beamline has begun in operation at the SACLA. More than one experiment became operational at the same period by using the dedicated experimental hutches for these beamlines. The framework of DAQ system was therefore upgraded to handle multiple user experiments in parallel with these beamlines. The control and data stream were reorganized and were separated for each beamline. The networks are physically segmented per beamline so that the control commands for the experiment at one beamline should not be transmitted to the other, and that the bandwidth for the large data transmission should be ensured. The data are stored to the high-speed storages dedicated to each beamline. Both can handle 6 Gbps data rate per beamline at the data acquisition cycle of up to 60Hz. Thus we achieve 12 Gbps data rate with two beamlines. The data are finally stored to the hierarchical storage system of more than 6 PB capacity shared by all beamlines. The relational database server to accumulate the beam- and experimental-condition is shared by all beamlines without any performance issue. The upgraded DAQ system is highly scalable. It would be adaptable for the future upgrade of up to five beamlines.

New High Purity Germanium Detectors’ pre-amplifier electronics typically have two type of output signals, the “fast” output and the “slow” output signals. A high timing resolution at the fast output is enough to clearly resolve the charge collection profiles in the detector for single-site and multi-site events. At the same time the slow output provide high resolution and very reliable operation for need of spectra measurement. There are three slow and one fast signals for one HPGe detector and the correspond FADC readout electronics are needed for pulse digitalization. The slow signals need about 14-Bit, 100MHz FADC and the fast signals need about 12-Bit, 2GHz FADC for pulse digitalization, the correspond high speed, high band width real time buffer and trigger interface, readout bandwidth are also needed. For the HPGe readout, we designed the combo FADC readout system with mixed 8-Channel 14-Bit 100MHz FADC and 2-Channel 12-Bit 2GHz FADC and high speed 1600MHz 64-Bits DDR3 SDRAM buffer. The FADC AD9253 from ADI, ADC12D1000 from TI and Kintex XC7K325T 900 pins FPGA from Xilinx are used in this design. And the RAIN1000Z1 ZYNQ module we designed last year is used for put data from buffer to the PC with Giga Bits Ethernet. The RAIN1000Z1 module is running the embedded Linux, the actual throughput of Giga Bits Ethernet is about 650Mbps. The challenges include the PCB layout for 2GHz FADC and 1600MHz 64-Bit DDR3 SDRAM, the input data band width is about 59.2Gbps and the buffer band width is about 102.4Gbps, the FADC data can be saved in the DDR3 SDRAM buffer real time for analyze without any drop for some long time length events.

In this work, we have characterized the detection limit and quantitative accuracy of our Trans-PET® BioCaliburn® LH system, in order to evaluate the feasibility of applying small animal PET to in vitro studies. By employing small animal PET in vitro studies, the experiment procedures can be simplified, the differences arise from different testing time can be removed, the bridge between in vivo research and in vitro research can be established, and also, temporal measurements may be obtained at the cellular level. An in vitro cell uptake experiment with radioactivity lower than 1 µCi was performed with Monte Carlo simulation and also in the real world. Radioactivity concentrations ranging from 1 Bq to 10000 Bq for single-source and 10 Bq to 500 Bq for multi-source were used to determine the detection limit. The quantitative accuracy was verified by comparing PET image data with the true value (MC simulation) and gamma counter data (cell uptake experiment). The source with radioactivity of 1 Bq can be visualized in single-source test, as well as sources with 50 Bq radioactivity in multi-source test. The FDG retention determined by small animal PET and the gamma counter showed a good linear correlation (r2=0.9997). High degree of correlations was also observed between the original radioactivity and the sum value in ROI of the PET image (r2=0.9970 in multi-source test and r2=1.0000 in single-source test). Hence, it is concluded that the small animal PET has sufficient sensitivity and desirable quantitative accuracy for the in vitro cell uptake experiment.

Recently, there is growing interest in directly digitizing the scintillation pulses for developing PET detectors or systems. Having digital pulse samples, in principle one can apply nontrivial software algorithms to analyze them to either yield better detection results or create flexibility in detector design. Previously, we have proposed the MVT method for directly sampling the scintillation pulse and developed several kinds of digital PET detectors named basic detector modules (BDM). These detectors are highly modular; they directly output the resulting MVT samples via a RJ45 connector while adopting the UDP protocol and employing a uniform data format. For PET systems employing these detectors, single-event processing and coincidence filtering are all done in software; as a result, new processing/filtering methods can be readily introduced for improvement and upgrading. Therefore, we wish to provide a BDM based design architecture to enable quick setup of a PET system. We introduce a system geometry definition file, named the SG file, for user to define the types and number of the BDMs employed, as well as their positions and orientations. Processing of the MVT samples to yield single event information, coincidence filtering, data format conversion, image reconstruction and data/image analysis are carried out by separate software modules with standardized input and output definitions. As a result, they can be conveniently modified or replaced, and be put into cascade chains to provide desired processing. In this work, we present this BDM based system design architecture and also describe the BDMs that we have developed. We show two example systems, including an in-vitro trace radioactivity assay system and a preclinical PET imager, that adopt this design architecture.

In this article we present the implementation of a resource-saving 8-channels TDC in a FPGA device with r.m.s. value of the resolution around 20 ps. The measurement is performed according to the Nutt technique, i.e. using a tapped-delay-line (TDL) TDC for the fine measure and a counter for the coarse one. The system is composed of eight distinct TDL-TDCs, one per channel, and just one counter. Moreover, it is equipped with an edge detector able to sense the position of the transition propagating along the delay line within one clock cycle (3.2 ns). The system is interfaced outwards by means of a USB 3.0 communication gate. The host device is a Xilinx Kintex-7 FPGA, but the architecture can be easily migrated on different families both of Xilinx and Altera devices.

The PHENIX MPC-EX detector is a Si-W preshower extension to the existing PHENIX Muon Piston Calorimeter (MPC). It was fully installed in December 2014. This extension includes eight layers of alternating W absorber plates and mini-pad silicon sensor layers. The preshower tower consists of 8 sampling cells, each built of 2 mm thick W plate and a fine position-resolution Si layer. The 0.5 mm thick Si detectors are structured into 1.8 x 15 mm2 minipads, they are digitized using SVX4 ASICs. To achieve high dynamic range, the dual-gain readout scheme is used by connecting one minipad to two readout channels through two different decoupling capacitors. The gain ratio of 6:1 makes it possible to register signals from 0.1 MIP in the high sensitivity channels of front layers and up to 700 MIP in the low sensitivity channels of the back layers.

Recently proposed digital Silicon PhotoMultipliers (dSiPM) integrate arrays of Time-to-Digital Converters (TDC) thus providing multiple photon timestamps for each detected gamma. A considerable amount of data is generated and has to be processed to estimate the actual time of arrival (ToA) of the gamma. This is typically performed on the FPGA present on the controller board. The processing stages include: (i) back conversion from TDC code to time, (ii) sorting, (iii) finding the timestamp of the first scintillation photon, removing noisy events (dark counts), (iv) and final processing to extract the ToA. In this work we discuss the implementation of two architectures specifically designed for this purpose on a low power, low cost FPGA and analyze their impact in terms of device utilization and timing. The architectures have been tested with the data generated by the SPADnet-I sensor, a 8×16-pixel d-SiPM, that generates up to 256 photon timestamps for every detected gamma. The analysis reveals that sorting circuitry is the most challenging part of the architecture, both in terms of area occupancy and speed. An on-chip implementation is feasible, with the throughput limited by the large number of timestamps to analyze.

Advanced Virgo is the project to upgrade the Virgo interferometric detector of gravitational waves. The project is now in an advanced construction phase and the assembly and integration will be completed by the end of 2015. The goal of Advanced Virgo is the early detection of gravitational waves. A major upgrade consisted in the design of a new control electronics of the so called Super Attenuators, that manages all the sensors and actuators. We present a new compact A/D-D/A conversion and processing unit used in the Advanced Virgo control electronics upgrade. The Unit consists in an analog to digital conversion stage that samples the input signals. An Altera Cyclone IV GX FPGA collects, pre-processes and sends data to a Texas Instruments TMS320C6678 DSP using a PCI Express GEN1 link with 2 lanes at 2.5Gbps. The DSP processes data and sends outputs to the FPGA for feeding the digital to analog conversion stage. The unit is equipped with six low noise and distortion 4 MSPS - 24-Bit A/D converters and six low noise and distortion 24-Bit D/A converters with sampling rates up to 640 kHz in Direct Stream Digital (DSD) mode and 384 kHz in PCM mode. Two FPGA transceivers are used for PCI Express link while a third one is used for a custom data transmission optical link. The TMS320C6678 is a multi-core fixed and floating point architecture DSP, with eight cores running between 1 GHz and 1.25 GHz. The unit has a dedicated input to interface directly to GPS timing signals. It is pluggable into a custom MicroTCA backplane. Using multiple units, sharing the same MicroTCA backplane and communicating via up to 4 Serial RapidIO lanes at 5Gbps, it allows composing a flexible and modular system with a large number of channels suitable for the Avanced Virgo control electronics.

Dual-energy X-ray method has been widely used in medical image and security inspection. However, current dual-energy method for container inspection system in high-energy range (1-10 MeV) is mainly used for pure material discrimination by the a-curve, which provides inaccurate atomic number and thickness in the case of overlapped objects. Actually in medical domain where boundary x-ray energies do not exceed 1 MeV, a material decomposition method can provides accurate bone mineral density using surface equation theory. It means that in the case of overlapped material discrimination, the thickness of each material can be obtained if the atomic numbers are given. The goal of our research is to examine the feasibility and accuracy of this theory in container inspection system which uses high-energy dual-energy X-ray. The experiments were carried out on a container inspection system with 4 MeV / 7 MeV dual-energy for a-curve drawing and conic surface calibration. C, Al and Fe were used as basis materials. The coefficients of calibrated conic surface are used to obtain the mass thickness of each basis material. The a-curve is used to reconstruct the dual-energy data of each material. Then the distribution of each material in the image can be obtained using this algorithm. We quantitatively analyze the accuracy and noise in the case of different material combinations and thickness, then discuss the results of original discrimination method and this theory.

Mobile radiation detector systems are meant to effectively detect the presence of sources of dangerous radiation while minimizing the frequency of false alerts. Our Bayesian Aggregation (BA) framework allows for sensor fusion of a variety of sensing modalities to enable detection of radioactive sources as well as inference of their properties. In this study, we extend the BA framework to enable online monitoring of sensor reliability. Sensor failures can arise both from internal system failure (e.g. a broken detector crystal) and external environment changes (e.g. gain drift). Both can cause spurious false alarms and detection misses. Statistically modeling sensor failure data can help robustify detection performance against such occurrences. By augmenting BA with explicit sensor failure models and hypotheses, incorporating a Hidden Markov Model (HMM) to estimate and track sensor working/failure state at each time step, and using the Forward-Backward algorithm to retrospectively smooth out posterior probabilities given new data clues, we hope to enable more fault-tolerant and resilient threat detection.

Mobile radiation detector systems are used to detect the presence of sources of dangerous radiation. Efficiently searching over large numbers of source hypotheses is a major computation challenge since a source scene may have many possible source location hypotheses. Additionally, sources can have many other characteristic parameters such as intensity and type. Bayesian Aggregation (BA) allows simultaneous detection of radiation sources and inference of properties. In this study, we develop Anomaly-Match BA (AM-BA), a BA variant that saves computation in searching parameter spaces of source hypotheses.

Anomaly detectors and match filters are background estimators commonly used on radiation observations to separate estimated source components from typical background fluctuation. Anomaly detectors assume no knowledge of the source, simply finding anomalies to typical background fluctuation. Match filters, in contrast, use knowledge of a source template or design in estimating components. Both types of estimators are useful in BA for estimating and assembling distributions of the Signal-to-Noise Ratio (SNR) of measurements. In AM-BA, anomaly filters are first used to prune parts of the source location hypothesis space that are not likely to contain the source. Match filtering parameter optimization for other source parameters (e.g. intensity and type) is subsequently run on the smaller space of source hypotheses. The developed algorithm can save significant amounts of computation in searching the space of source parameter hypotheses without loss of threat detection capability.

We report the development of data acquisition (DAQ) system for next generation X-Ray sensor in the SPring-8 Angstrom Compact free electron LAser (SACLA) facility. A next generation X-ray sensor, the SOI photon imaging array sensor (SOPHIAS), based on the silicon on insulator (SOI) technology, has been developed in SACLA facility. SOPHIAS has larger number of pixels and higher dynamic range of signal compared to the current X-Ray sensor, Multi-Port Charge Coupled Device (MPCCD), in SACLA facility. It can acquire 16 MB/frame image data, which is 16 times larger than that of MPCCD, leading the data transfer rate of about 3.8Gbps for the data collection rate of 30Hz. We have developed new DAQ system for SOPHIAS in SACLA facility. The detector composed of two new X-ray sensors will be provided in SACLA facility. The network band width has to have ten Gbps. The new DAQ system for the detector consists of two computer servers with a new frame grabber board and a ten Gbps network interface card, tag data distributor, network switch, and high-speed data storages. The new frame grabber board satisfies the following requirements. 1.The board has Camera Link full-configuration interface and perform online data quality check using cyclic redundancy check keeping the data transfer rate of about 3.8Gbps. 2.The tag information provided by the tag data distributor has been embedded into the SOPHIAS data to guarantee the data identification at the same beam shot. 3.The board has PCI express interface and can attach to 1U 19-inch rack-mount server to reuse the existing server resources. Selection of the FPGA and connectors are carefully done to reduce costs of the board and to save board size. The new X-ray sensor provides signal and background data pixel by pixel. We perform online subtraction of the background data form signal data to reduce the data size to send to the high-speed data storage. The performance test of DAQ system has done and the results satisfy our requirements.

Thomson scattering (TS) is one of crucial plasma diagnostics providing key data for many experimental studies and widely used method to measure electron temperature and density in fusion-oriented plasma experiments. TS is important diagnostic to the success of many modern plasma experiments and systems including ITER. The small power (~10-8W) and short duration (~10 ns and less) of scattering signal are the main technical problems of the diagnostic. Thatï¿½s why highest requirements are made to photodetection and data acquisition (DAQ) systems.
The report desribes the uniquely designed complex TS DAQ systems which allows recording short duration (3-5 ns) scattered pulses with 2GHz sampling rate and 10-bit total resolution in oscilloscope mode. The system consists of photo detector modules with 0-200MHz bandwidth, simultaneously sampling ADC modules and synchronization subsystem. The photo detector modules are based on avalanche photodiodes (APD) and ultra-low noise transimpedance amplifiers. ADC modules include fast analog to digital convertors and digital units based on the Field-Programmable Gate Array (FPGA) for data processing and storage. The synchronization subsystem is used to form triggering pulses and to organize the simultaneously mode of ADC modules operation.
The 48-channel version of this system was developed as a prototype for ITER (Cadarache, France) divertor TS and was tested on GLOBUS tokamak (St. Petersburg, Russia).

The Trigger and Data Acquisition (TDAQ) system of the ATLAS detector at the Large Hadron Collider (LHC) at CERN is composed of a large number of distributed hardware and software components (about 3000 machines and more than 15000 concurrent processes at the end of LHCï¿½s Run I) which in a coordinated manner provide the data-taking functionality of the overall system. The Controls and Configuration (CC) software offers services to configure, control and monitor the TDAQ system. It is a framework which provides essentially the glue that holds the various sub-systems together. While the overall architecture, established at the end of the 90ï¿½s, has proven to be solid and flexible, many software components (from core services, like the Run Control and the error management system, to end- user tools) have undergone a complete redesign or re-implementation during the LHCï¿½s Long Shutdown I period. The upgrades were driven by the need to fold-in the additional requirements that appeared in the course of LHCï¿½s Run 1, to profit from new technologies and to re-factor and cleanup the code. This paper describes the approach that was taken to plan, organize and carry out this software upgrade project. It highlights the main technical choices that have guided the overall work, describes the major achievements and outlines how the CC software may be further improved or re-shaped in the future.

Several X-ray spectroscopy applications (e.g. at synchrotron facilities or adopting high-power X-ray tube generator) require detection systems operating with high energy resolution and high counting rate capability. The use of silicon PIN or Silicon Drift Detectors (SDDs) is often the best option to cope with such demanding requirements. In order to meet this requirement, it is necessary to read out such detectors with very short processing times. In the recent years, new preamplifiers, like CUBE, have been designed to provide improved energy resolution at short processing times. Nevertheless, in order to fully benefit from this, the DPP (Digital Pulse Processor) read-out electronics has to provide short processing time adding a negligible contribution to the overall measurement noise. A new DPP, developed for high resolution and ultra-fast spectroscopy, will be presented. The system is suitable and optimised for spectrometers based on last generation SDDs equipped with CUBE preamplifier, but it can be used with silicon PIN diodes, or any other X and Gamma-ray detector equipped with CUBE. The effective pile-up rejection strategy enables to efficiently detect pile-up and maximize the throughput for a given processing time up to an input count rate of 3Mcps. The achievable energy resolutions, using different reference SDD detectors at different count-rates, will be shown. A remarkably good energy resolution at 6 keV of 155 eV at 110ns peaking-time has been obtained. Such short peaking time enables the operation up to 3Mcps of input count-rate. The performances of the DPP in critical measurement conditions, like the energy resolution with dead-time close to 99%, will be presented as well.

We introduce an improved version of the Digital Detector Emulator able to generate programmable analog shapes with a rise time up to 1 ns. This is suitable for all the fast-scintillator emulation environments. Moreover, the output dynamic of 16 bits allows the device to be used in high resolution spectroscopy applications. The instrument is not a pulse generator of recorded shapes but a synthesizer of random pulses compliant to programmable statistics for height and starting time of events. The device also features programmable noise sources, disturbances and baseline variations. The implementation of an analog input channel allows the instruments to mix the emulated signals to real signals sampled by the input channel.

n this contribution we introduce an innovative instrument for the education world to be used in physics and medical imaging courses. The instrument is able to generate analog signals with the same characteristics of the output of a real radiation detector under the influence of one or more radiation sources. Lot of experiments can be conducted when the educational detector emulator is connected to a digitizer or to a MCA.

We present a compact Multi Channel Analyzer that can be used in applications for energy measurements that range from X to Gamma ray spectroscopy for different types of detectors and preamps with continuous and pulsed reset. Main features of the instrument are the extreme compactness and the portability that make it suited both for laboratory and portable applications. It offers extreme versatility in power supply being able to use several power sources, i.e. electrical network, USB, Power over Ethernet, Lithium battery, solar panels. It can be directly interfaced with PC, Android-based devices and Apple devices via USB, Ethernet, WiFi and Bluetooth connectivity. The instrument has been fully engineered and characterized.

During the first LHC Run, the CMS collaboration introduced data scouting as an alternative strategy to data taking, allowing to take data that othwerwise would be rejected by the trigger filters. This special data flow, based on event-size reduction rather than event filtering, was exercised to maintain sensitivity to new light resonances decaying to jets, with very small resources allocated to it. The challenges implied by this new workflow and the solutions developed within the CMS experiment are reviewed. An outlook of data scouting for the second LHC Run is given.

To accommodate the needs of PET imaging systems with different geometries and configurations, a new data acquisition system has been designed based on customized ASICs and FPGAs with 3 modularized detector, detector-panel (or panel) and PET (or system) levels. Detector level consists of front-end readout electronics with each one having 64 readout channels with four 16-ch ASIC chips to convert analog signals to timing-based digial pulses. An on-board FPGA decodes these timing signals to interaction energy, timging and positioning information and transfer them to a panel-board for further processing. Each panel-board can handle 6 detector-boards for detector calibration and on-line calculation of overall multi-interaction event energy, timing and position. The data were further transferred to the system-board for coincidence event selection and data transfer to acquisition computer through a PCI-E with 100MB/s transfer rate. The inter-board data were transferred through LVDS cables with 1Gb/s rate. The system can support upto 3072 simultaneous input channels with each counting rate >500k/s. Overall coincidence counting rate can achieve >10M/s. System is scalable with different channles through configurations of three different levels, leading to flexibility of different detector numbers and configurations. The energy measurement resolution is up to 11 bits and the event timing measurement bin width is 0.3ns with accuracy (FWHM) ~0.6ns. The timing stamp for event time record ranges more than years for long time data acquisition needs. Prelimnary testing for PET detector showed good performance of energy, crystal identification, timing and other measurements. The overall acquisition is compact, and can be arranged flexibly with relatively long cable connections. Besides ASIC chips, data acquisition were developed using off the shelf components for low cost and upgradability. The system can also applied to other related nuclear electronics data acquisition.

Iodine-131 has been widely used in nuclear medicine therapy. Quantification of I-131 remained in patients is important in monitoring and managing the patient after treatment. Therefore, the selection of suitable radiation detector has been needed in clinical environment. Survey meter and gamma probe detector have been used in patient management. In this study, we compared the detection performance of gamma probe detector and survey meter in the phantom study using high dose of I-131. In the phantom study, we used FHT6020 and GammaPro 1410 as a survey meter and digital gamma probe respectively. We used 14 vials containing I-131, and made various activities (10-300 mCi). Activity measurement was conducted at the distance of 3m and 1.5m respectively. We used plastic packs filled water as attenuator. For the probe detector, based on the three kinds of energy window set around the main photopeak (364 keV ± 15, 20, 30%) and total energy range, we compared several parameters. In both devices, the measured counts showed tendency of underestimation as source activities were increased. The amount of underestimation by survey meter (27% @ 200 mCi, 30% @ 300 mCi) was relatively larger than that by gamma probe detector (21% @ 200 mCi, 23% @ 300 mCi) in the measurement at 3 m distance with attenuator. However, there was no significant difference for both measurement at 1.5 m with attenuator and 3 m without attenuator. In the case of gamma probe, as activity was increased, the amount of scatter (0 - 315 keV) showed a downward tendency. And, background counts in high energy (0.65 – 3 MeV) showed a upward tendency. Compare to the other widths, counts error rate of 30 % widths had lower counts error. These results showed that both devices should consider the dead time effect in the measurement of I-131 radioactivity in patients. And the use of gamma probe detector can be more useful in quantitative measurement of I-131, by means of optimization of acquisition parameter.

As luminosity continues to increase in high-energy physics experiments, signal pileup has become a significant limiting factor for accurate energy measurement. A sequence detection algorithm is presented in this paper for pulse amplitude (proportional to the deposited energy) estimation in ionizing calorimeters using the decision feedback technique and the m-tuple linear optimal filter (LOF) [2] to treat the pileup events from the past (i.e., history inter-event interference or IEI) and those from the future (i.e., future IEI), respectively. The systematic truncation error of the LOF of [2] is mitigated by an iterative LOF extension. Accurate energy measurement results obtained from computer simulations verify the validity and performance of the algorithm. A cursory comparison of the proposed algorithm with the original LOF of [3] is also conducted, with the results summarized toward the end of the paper.

This study investigates the effect of energy threshold on being able to include and position multiple-interaction photon events (MIPEs) detected in a cadmium zinc telluride (CZT) based small animal PET system we have built. Due to noise fluctuations, each channel’s data acquisition trigger threshold should be adjusted above the noise floor, which limits the detection of photon interactions with energy below the threshold. If not identified, these events will lead to a loss of photon sensitivity as well as reconstructed image spatial resolution and/or contrast. GATE simulations with a cylinder having four hot rods were carried out and it was shown that for an energy threshold of 50 keV and above, at least 14% of events will be mispositioned due to the loss of first and/or second interaction in MIPEs. Compton kinematics is leveraged to mitigate this problem by classifying mispositioned trues, in addition to random and (phantom) scatter events through the use of a novel “angular threshold” which maximizes a figure of merit inspired by noise equivalent counts. An angular threshold of 3° was found to detect 63% of mispositioned MIPEs, along with 80% of randoms and 66% of scatters with system energy resolution of 7.4% FWHM and system time resolution of 30 ns FWHM. The simulation results will be used to guide data processing of experimental phantom results.

This work presents a new method to measure Cherenkov photons being generated in lead glass from interactions of 511 keV gamma-rays. The crystal (3.2x3.8x15 mm3) is coupled one-to-one to a pixel of a digital SiPM. The readout of the lead glass is triggered by a master scintillator coupled to a pixel in the same tile using the neighbor logic of the sensor. Cherenkov photons are generated by applying 4 different sources over the lead glass: ¹⁸F with 50, 30 and 15 MBq and ²²Na with 2.8 MBq. A control measurement without source is performed as well. Each configuration is repeated 10 times, for 6 different temperatures (-5 to 20 degrees) and 8 integration lengths (0 to 325 ns). The subtraction of the dark-count background (control) from the measurements with sources (Cherenkov and dark-counts) gives the signal produced solely by the measured Cherenkov photons. The results at -5 degrees show a proportional behavior between the source activity and the gain of the background-corrected Cherenkov signal, being consistent with different sensor configurations. With the 50 MBq source, in over 5% of all events a Cherenkov signal with up to 5 photons is detected. This low percentage is due to a large number of events with no registered activity in the lead glass pixel. One cause for this is the low number of Cherenkov photons arriving at the detector. Another relevant factor is an intrinsic property of the neighbor logic, causing the lead glass pixel to frequently ignore the master trigger. Depending on the setup configuration, the events without activity amount for 45% to 80% of all events. The Cherenkov signal can be detected at 20 degrees, although inconsistent with the source activity. This is due to an unstable control of high temperatures of the used setup, causing variations in the dark-count rate of the sensor. A low DCR is crucial for the accuracy of the proposed method. Further experiments are being performed to increase the detection rate of the implemented approach.

The Vacuum Silicon PhotoMultiplier Tube (VSiPMT) is a new concept of photodetector based on the combination of the outstanding performances of SiPMs and the large sensitive surfaces of PMTs. Such device is made of a PMT standard envelope, with a photocathode for photon-electron conversion and an electrostatic focusing system that accelerates and focuses the generated photoelectrons towards a small focal area covered by a SiPM. The electron multiplication stage is the heart of the device and represents the real innovation with respect to the standard PMT technology. Therefore, a huge preliminary work aimed at the study of the performances of SiPMs as electron multipliers has been mandatory in order to investigate the feasibility of the VSiPMT. The extremely positive results achieved in this phase encouraged Hamamatsu Photonics to realize some prototypes of VSiPMT, that have been extensively characterized in the laboratories of INFN – Section of Naples. In this presentation some highlights about the main milestones of the project will be provided. In particular, taking as a starting point the results of the prototype characterization, the so-called “phase 2” aimed at the realization of a new optimized generation of VSiPMT prototypes will be discussed.

Silicon Photomultipliers (SiPMs) are rapidly developing photosensitive devices which are already used as an alternative to photomultipliers (PMT) in the newly developed calorimeters for high-energy physics. Many measurement results and SIPMs parameters based on signal amplitude histograms analysis have been published. Author presents a special automated system for scanning SIPMs surfaces with a fast amplifier. The system has been developed in order to examine shape of signal response dependency on position of photons hits on the surface of the detector.

Since the early days of experimental particles physics photomultipliers have played an important role in detector design. Also in astroparticle physics research, photomultipliers are largely used, in particular in experiments employing the technique of the detection of Cherenkov photons. Currently, the KM3NeT Collaboration is building a water Cherenkov neutrino telescope in the Mediterranean Sea based on the next generation optical modules with multiple low price 3-inch photomultiplier tubes. In its final layout, the KM3NeT neutrino telescope will host several hundred thousand photomultipliers, which must be tested and calibrated during the production of the optical modules. To overcome a possible bottleneck in the production process of testing and calibration of the massive amount of photomultipliers for KM3NeT, we developed the Dark Box instrument to accelerate the process. The Dark Box setup is designed to provide fast simultaneous automatic testing of 62 photomultipliers to verify their compliance to requirements for timing and ToT resolution and the occurrence of spurious pulses. In addition, the Dark Box can be easily converted into a general instrument for testing and calibrating large amounts of photomultipliers other than those for KM3NeT. We report on the design and performance of the Dark Box instrument for the high-statistics measurement of the characteristics of photomultipliers and of their calibration.

SPADnet is a sensor platform for the detection and processing of gamma photons generated in a PET system. SPADnet uses the novel technique of deferred coincidence detection, whereas timestamps associated with gamma events and their energy are routed at high speed (up to 3.3 million events per second) over a 2Gbps network, along with synchronization information. In this work, we describe SPADnet’s key building block, a tile of SPADnet-I chips. SPADnet-I is a 50 mm², 8×16 pixel digital SiPM where each pixel includes an array of 720 SPADs and the logic to count photons and record their arrival time. A fill factor of 42.9% is achieved. A distributed adder provides the number of photons detected throughout the whole array every 10 ns. On-chip triggering logic monitors this value in real time to discriminate gamma events from dark counts. The chip features a 10.8% energy resolution and a CRT of 288ps when coupled to a 3×3×10 mm³ LYSO crystal. High spatial resolution is obtained by combining the data generated by each pixel to efficiently locate the gamma absorption in the 2D space even when coupled to large arrays of crystal needles as small as 1.12×1.12mm². The tile is built on a 5×5 array of SPADnet-I sensors. A Xilinx Spartan6 FPGA controls the whole module and monitors the gamma activity across the 25 sensors. Here, the large amount of data generated for each detected gamma is processed in real time to extract energy, position and time-of-arrival. Pile-up detection and energy windowing are applied to the events, which are then fed to a network of tiles for coincidence detection. A centralized snooper recognizes coincidence pairs while thermal, Compton, and single events are discarded. The system is inherently scalable, as it enables single- or multi-rings of photonic modules for potentially large PET systems.

A recently proposed XOR-based Digital Silicon Photomultiplier is compared against the OR-based counterpart. We show experimental data from a set of SPAD pixel arrays in 130nm CMOS process with selectable OR tree and XOR tree for direct comparison. We demonstrate how XOR-based dSiPMs solve the limitation caused by monostable circuits and reach maximum count rates of at least a factor of two higher compared to optimised OR-based dSiPMs. The increased throughput of the SPAD array allows higher sampling rates for the digitisation of the light signal improving the overall performance of typical PET systems.

Single photon avalanche diodes (SPAD) are silicon based detector used for many applications requiring high timing resolution and single photon sensitivity. Applications such as time-imaging calorimeter and positron emission tomography (PET) benefit from better timing resolution to integrate time-of-flight (TOF) measurements. To obtain high timing resolution with TOF capabilities, a 3D single photon counting module (3DSPCM) is proposed. The top layer with SPAD could be fabricated in an optoelectronics process or CMOS process with high fill factor. A finer technology node will be used for the bottom layer, enabling the integration of a time-to-digital converter (TDC) with high timing resolution and a quenching circuit (QC) with advanced front-end to optimize the timing measurements of each SPAD. In this paper, we present the QC designed in TSMC CMOS 65 nm to be integrated in the 3DSPCM developed at Université de Sherbrooke. An open-loop operational amplifier (OA) was used as a fast comparator for the QC. The OA has an adjustable threshold from few mV up to 2.5 V to select the optimal voltage threshold in the rise time of the SPAD signal seen by the QC. The OA was designed to obtain both low walk and low jitter as a function of the input signal variation. Measurements of the QC show a 4 ps FWHM timing jitter. Three SPAD with an 8 µm diameter have also been designed in CMOS 65 nm to test the QC architecture in 2D for a more realistic characterization of the circuit. The measurements show a 13 ps FWHM single photon timing resolution (SPTR) at 1.5V of excess voltage. The QC has a total size of 30 × 18 µm² including the top contact for the through silicon via (TSV) connection of the 3DSPCM architecture. This QC has been designed to optimize the performances of the SPAD integrated in 3D knowing they will be implemented in different architectures, sizes and technologies.

Silicon Drift Detectors (SDDs) and Silicon PhotoMultipliers (SiPMs) are two silicon based photo-detector technologies for scintillator readout with applications in medical imaging, nuclear physics and space research. These devices provide compact scintillator readout solutions for spectroscopy, imaging and timing measurements. Goal of this work, is to make a comparison between these two photo-detector technologies, in particular for gamma-ray spectroscopy measurements. SDDs are characterized by very high quantum efficiency (> 80%) with no multiplication which helps to keep the statistical contribution to the energy resolution close to Poisson limit but, at the same time, makes the system very sensitive to readout electronics noise. SiPM devices on the other hand, have a very high multiplication gain (10^5 - 10^6) which makes the electronics noise contribution almost negligible, with only the dark count rate contribution which can be reduced with moderate cooling. However, they are characterized by lower Photo Detection Efficiency (PDE) ~30-40% and statistical spread of the multiplication gain. In order to compare the spectroscopy performances of the two photo-detectors, we evaluate the energy resolution achievable with them using a large Lanthanum Bromide scintillator. Expected energy resolution with 2” LaBr3:Ce and its sensitivity to various parameters of SDDs and SiPMs are evaluated to analyze the photo-detector performances. With SDD arrays of 2 nA/cm^2 leakage current technology, an energy resolution of 3.38 % has been measured at -25 °C with Cs-137 source at a shaper peaking time of 6 µs. Experimental results using the same 2’’ LaBr3:Ce scintillator coupled with arrays of 144 SiPMs will be presented to validate the theoretical energy resolution estimates and to compare the two readout technologies.

This work presents a model describing the IV characteristics of SiPM detectors allowing to determine important physics parameters like breakdown voltage V_BD and triggering probability P_Geiger. The proposed model provides a good description of experimental data taken with SiPMs of different technologies (i.e. Hamamatsu HPK, KETEK) and geometries. Over a very wide range of current (i.e. 10^-11A up to 10^-4 A) only a few nA of difference were observed between the experimental and calculated values. Silvaco TCAD simulation tool was used to acquire further insights into the physics behind the IV curves and to identify the different components of DC current (i.e. thermal generated carriers, tunneling, afterpulses). The results are shown to be in good agreement with V_BD and P_Geiger determined from AC measurement.

This work focuses on the development of novel nano-engineered microchannel plates (MCPs) to enhance a new generation of NUV-visible light photon counting detectors that have a wide range of applications in LIDAR, 3D topographic imaging, high-speed photography, bio-medial fluorescence microscopy and astronomical imaging. The MCPs are borosilicate glass micro-capillary arrays functionalized using atomic layer deposition (ALD). MCP’s manufactured in this way have many advantageous properties, including the ability to withstand high processing temperatures, high secondary electron yield, and low outgassing. This scheme has the ability to support higher global photon count rates while greatly reducing the deterioration of photocathode efficiency and detector gain. Opaque photocathodes have been deposited onto these nano-engineered borosilicate MCPs and several sealed tube devices have been constructed. Here we report on the progress of this effort, including performance and lifetime characteristics from the sealed tubes and MCPs, and results from the deposition of opaque photocathodes onto nano-engineered MCPs.

Single Photon Avalanche Diode (SPAD) arrays made in CMOS technologies are of high interest in high energy physics and medical imaging. HV CMOS processes are suitable for SPAD implementation and are low cost, which is particularly interesting for large area detectors. We report on process modifications made in a standard 0.8 µm HV CMOS technology to implement SPAD arrays dedicated to 3D integration. The modifications concern the SPAD p₊n junction profile and aim to reduce the dark count rate (DCR) and increase the photon detection efficiency (PDE). Three variations are studied. The SPAD cathode concentration is reduced to avoid dark counts caused by band to band tunneling. The SPAD junction depth is moved toward the surface to increase the PDE for the 400-480 nm wavelengths. The SPAD p₊ ion type is modified to lower the defect concentration caused by the p₊ implantation. Dopants and electrical profiles of the SPAD were modeled prior to the fabrication. Six wafers have been implemented, where one is the standard process while others contain process modifications. SPAD I-V curve characterization shows an increase of the breakdown voltage from 19.5 V up to 29.2 V thanks to the n well concentration reduction. DCR and PDE as a function of the excess voltage and the wavelength are presented. Particularly, the n well modification leads to a DCR reduction and the p₊ ion modification decreases the afterpulsing probability. The results obtained in this low cost HV CMOS technology make it suitable for SPAD arrays fabrication and it will be integrated in 3D with low consumption or high performance CMOS readout electronics, according to the application.

The 3D integration of Single Photon Counting Module (SPCM) where a Single Photon Avalanche Diode (SPAD) array is stacked over an array of quenching circuits is the best configuration to obtain a greater photosensitive surface without having to compromise on readout electronics. In this configuration each SPAD and quenching circuits are interconnected with Trough Silicon Vias (TSV) that are implemented after the commercial fabrication of the dies. For the first 3DSPCM prototype, each tier is fabricated in a commercial CMOS process and post-process microfabrication steps are required to achieve the assembly of the 3D integrated module. The required microfabrication steps include the TSV etching and metallization, the interconnections to the CMOS metals, the grinding of the substrate, the interconnection pad fabrication as well as the bonding process to realize the final assembly. The study of the possible impact on SPAD characteristics is essential to the development of 3DSPCM. We report on the measurements of 216 SPAD from 18 dies coming from the same wafer to study the possible impact of these microfabrication processes on the excess voltage, the dark count rate, the afterpulsing and the PDE of the SPAD.

With the increased use of Single Photon Avalanche Diodes (SPAD) in analog and digital SiPM for PET instrumentation, it becomes essential to study in depth the impact of design parameters on performance, particularly time resolution. To this end we have implemented a SPAD array simulator to perform parametric studies of SPAD array geometries. Using this simulator, optimal SPAD array active readout schemes for a PET detector have been investigated. Parametric simulations were done for the pixel size, array size as well as SPAD junction depth, thickness and operating point for a SPAD array in Teledyne DALSA 0.8 µm HV CMOS technology. Multiple readout strategies were tested and compared, including fixed threshold, constant fraction discriminator, quadrants, and maximum likelihood estimator, to compare their performance. An average time of arrival of the first photons shows a time resolution approaching 100 ps for pixel sizes over 70 µm while the quadrant strategy performs best with pixels in the range of 50 to 70 µm. Thus, the optimal pixel size strongly depends on the readout strategy used. Considering the ongoing interest for SiPM, the same procedure was applied to obtain the optimal SPAD array geometry configuration for a SiPM in the same technology.

STiC3 is a mixed mode Application Specific Integrated Circuit (ASIC) for high resolution timing readout of Silicon Photomultipliers (SiPMs). It is designed for Time-of-Flight (ToF) applications in medical imaging and High Energy Physics experiments and has been developed in the frame work of EndoToFPET-US project. The STiC3 chip uses the UMC 180 nm CMOS technology and has a differential structured front-end to reject common-mode noise. It has 64 channels and each channel consists of analog front-end, a build-in TDC module and a digital part. In earlier measurements using 3.1x3.1x15mm3 LYSO crystals and Hamamatsu S10362-33-050C MPPC sensors, a Coincidence Time Resolution (CTR) of ~214 ps FWHM has been obtain; the achieved energy resolution is ~12% for 511 keV photons. In order to explore the timing performance for small signals a special setup has been established in our laboratory. The setup includes an optical system for automatically focusing a laser beam to a spot size smaller than 3 um and allows to precisely evaluate the performance of the STiC3 chip as well as to carryout SiPMs characterization studies. A first measurement of the Single Photon Time Resolution (SPTR) using STiC3 is presented in this paper.

Alkali antimonide photocathodes are a subject of active research owing to its high quantum efficiency in the visible region and has impacted a wide range of instruments including photomultiplier tubes, image intensifiers and high-brightness accelerators. These antimonide photocathodes are a strong contender for the next-generation photon sources such as LCLS II or the XFEL. However, only recently have modern synchrotron techniques enabled a systematic study of the chemistry for the formation of these materials. Such analysis has led to the understanding that these materials are inherently rough when grown through the traditional sequential deposition; this roughness has a detrimental impact on the intrinsic emittance of the emitted electron beam. Sputter deposition provides a viable path to achieve a smooth photocathode, while maintaining reasonable quantum efficiency. To the best of our knowledge, we report for the first time on the fabrication and vacuum transport of a stoichiometric K₂CsSb sputter target, and its use to create an ultra-smooth (< 1 nm) cathode thin film that demonstrated a photoresponse over a wide wavelength range. This result may potentially lead to low-emittance photocathodes for the next generation light sources.

Emerging UV to blue light emitting scintillation materials promise improved radiation detection capabilities such as dual neutron-gamma detection and higher energy resolution. The use of traditional photomultiplier tubes (PMTs), with their associated high-voltage electronics often represents form factor and power-limiting component. The unique capabilities of a solid-state photomultiplier (SSPM) provides an alternative to PMTs. Though SSPMs have been gaining wide attention in recent years, a major limiting factor is the dark current, especially for detectors that require sufficiently large detection area. To scale up the detector area without drastic increase in dark current, we are developing new photodetector elements in Al_0.8Ga_0.2As, a ternary semiconductor material with an indirect band-gap energy of ~2.1eV. The wide-band-gap characteristic combines with the maturity of GaAs material processing makes Al_0.8Ga_0.2As an excellent material for developing large area SSPMs with lower dark current. The 80% aluminum concentration optimizes the band-gap to the emission wavelengths of high performance scintillation materials, to provide a photodetector with the lowest possible dark current. With a proper device structure, the AlGaAs SSPM is expected to provide a smaller dark current with high detection efficiency within the blue to UV region, which is important for state-of-the-art scintillation materials, such as LaBr₃, CeBr₃, and CLYC. Utilizing commercial AlGaAs epitaxial wafers, prototype Geiger-mode photodiode elements have been designed and fabricated. Mesa photodiode structures are developed with predicted breakdown voltages and low dark count rates. This work presents the design, fabrication, and characterization results of sample devices. Comparisons between different geometries, doping structures, and fabrication techniques are discussed for the optimization of the device optical, electrical, and noise performance.

The GlueX detector in Hall D at Jefferson Lab has been instrumented with about 5000 Silicon Photomultipliers (SiPM) manufactured by Hamamatsu Corporation. Silicon photomultipliers with a sensitive area of 3x3 mm2 are used to detect light from scintillator detectors such as: the tagger microscope, pair spectrometer, and start counter. An array of 4x4 SiPM sensors was specially designed by Hamamatsu for the instrumentation of the barrel electromagnetic calorimeter. SiPMs in the tagger microscope and start counter will be operated at a relatively large rate up to 2 MHz. We performed measurements of the time resolution for different SiPM operation rates and estimated the SiPM pixel recovery time. Time characteristics were compared for sensors with two pixel sizes: 25 µm (MPPC S12572-025P) and 50 µm (MPPC S12572-050). Time resolution of the SiPM array (MPPC S12045) was measured as a function of light for several SiPM temperatures. Studies were performed using a picoseconds laser light pulser and a light-emitting diode.

A novel silicon photomultipliers (SiPM ) has been developed with both a standard and a fast output, aiming at providing good energy and timing performance simultaneously for time of flight (TOF) PET application. Optimal readout method of this SiPM is investigated in this study. The standard output can be taken from either anode terminal or cathode terminal and different dual readout mode has different impact on timing resoultion of fast output. Three dual readout modes were evaluated and we found the optimized way was to readout the standard output on the cathode side with a small capacitance in parallel. This readout mode can preserve good timing performance using relatively few electronic components. We developed a detector module by directly coupling a 16x16 LYSO crystal block to an 8x8 Sensl FC30035 SiPM array. Through multiplexing and summing scheme and charge division resistor network, 64 channels of fast output and 64 channels of standard output are reduced to one fast timing signal and four energy signals, making the detector highly compact and scalable. The performance of the detector module was evaluated. 16×16 LYSO crystals were well resolved in the flood image and the average energy resolution were 12.4%±0.8% at 511 KeV. The average coincidence resolving timing (CRT) of the block against a single LYSO crystal coupled to a FC30035 pixel were 286± 13 ps. The average block-to-block CRT were estimated to be 311 ps .The proposed dual readout design has demonstrated excellent timing performance for TOF PET detectors.

Digital Silicon Photomultiplier (d-SiPM) has recently emerged as a promising photodetector technology for the development of Time-of-Flight (ToF) Positron Emission Tomography (PET) systems. It not only addresses a number of challenges encountered by its analog counterpart (i.e. the conventional analog SiPM) such as power consumption and noise susceptibility, but also provides additional benefits including low cost, high yield, high reliability and sensor-on-chip integration. Furthermore, due to its compatibility with standard CMOS technology, it is possible to monolithically integrate the single-photon avalanche photodiode (SPAD) micro-cells on the same substrate with complex electronics required for quenching, analog-to-digital conversion, time-to-digital conversion, digital photon counting, data storage and transfer [1], [2]. In our study, a high-resolution, ultra-low power and high linearity time-to-digital converter (TDC) is implemented to improve the timing information, a critical parameter for ToF PET imaging applications [3]. The resolution of this ToF measurement has a direct impact on the signal-to-noise ratio (SNR) and contrast of the reconstructed image. SPADs are chosen as the detector due to their high sensitivity, high gain, and fast timing properties [4], [5]. Other design considerations include compact size and low power consumption, which becomes more important when a large number of SPADs, TDCs and associated circuitry being integrated to form the dSiPM. In this work, we report on the design of a novel 8×8 SPAD array implemented in 130nm mainstream digital CMOS technology with integrated in-pixel peripheral circuitry, such as the quenching and resetting circuits, 1bit-ADC, voltage-conversion and read-out circuits. We also report our design of a TDC based on gateable Vernier ring oscillator architecture featuring high resolution and low power consumption, which is dedicated for the integration with the SPAD array to form the d-SiPM sensor.

A study has been carried out to investigate the effects of radiation damage in SiPMs for potential use in various detector upgrades for the PHENIX experiment at RHIC. As possible sensors for the proposed sPHENIX calorimeters, we have examined a variety of SIPMs and characterized the changes in their performance before, during, and after irradiation, to understand how these changes will affect the performance of the calorimeters over time. Through completed and ongoing studies of different SIPM devices and device configurations such as micropixel size and count, device architecture and encapsulation, and system temperature control, we seek to minimize and mitigate the effects of radiation damage in SIPMs, understand their limitations, and assess their suitability for use in calorimetry applications.

Majority of papers concerning scintillation detectors with light readout by means of silicon photomultipliers refer to nuclear medicine or radiation monitoring devices in which energy of detected gamma rays is below 2MeV. However, detection of radiation with higher energies is also important e.g. in high energy physics or in plasma diagnostics. The aim of this paper is to study usefulness of SiPM light readout in detection of gamma rays up to 6.1MeV in combination with various scintillators. The reported measurements were made with 3 samples of one type of Hamamatsu TSV (Through Silicon Via technology) MPPC arrays. These 4x4 channel arrays have a 50x50 µm² cell size and 12x12 mm² effective active area. All the tests were done in a climatic chamber. The following scintillators were used: CsI(Tl), LYSO, BGO, LaBr₃, CeBr₃, NaI(Tl). The studies are focused on optimization of the MPPC performance for practical use in detection of high energy gamma rays. The optimization includes selection of the optimum operating voltage in respect to the required energy resolution, dynamic range, linearity and pulse amplitude. The presented temperature tests show breakdown voltage dependence on the temperature change and define requirements for a power supply and stabilization method. The energy spectra for energies between 320keV and 6.1MeV are also presented and compared with data acquired with a classic photomultiplier. Such comparison allowed study of nonlinearity of the tested MPPCs, correction of the energy spectra and proper analysis of the energy resolution.

Our group has undertaken the development of 3D Single Photon Counting Modules (3DSPCM) in order to overcome some limitations encountered by SiPM. Increasing the dynamic range, maximizing the photosensitive area while integrating advanced functionalities such as power management and time stamping of individual events are among the foreseen improvements to enable timing resolution in the ~10 ps required by future imaging modalities. This paper presents the process developed to assemble 3D integrated prototypes from commercial CMOS ASIC, technological choices used for the Through Silicon Via (TSV) microfabrication, as well as the constraints associated with certain critical steps such as the TSV insulation by electrografting. The electrical performances of the TSV and 3D encapsulation are presented. We also discuss critical packaging considerations for the 3DSPCM that can lead to significant stress and possibly short device lifetime if not handled properly. Packaging solutions for room temperature operation are presented, as well as solutions for the more stringent case for cryogenic operation. The potential use of our 3D integration technology for prototyping other types of sensors used in radiation instrumentation is discussed in the conclusion.

Photomultipliers with alkali antimonide photocathodes have the capability of measuring very fast low light level signals, providing a wide range of applications in time-of-flight (TOF) systems, positron emission tomography (PET) and large Cherenkov detectors. An enhancement of the photocathode performance, especially its quantum efficiency would have significant impact on these application fields. Traditional bialkali photocathodes through diffusion growth process encounter material challenges and are being investigated using synchrotron to optimize their performance. Photocathode with peak quantum efficiency over 30% was achieved via co-evaporation growth method. External quantum efficiency enhancement method, such as reducing light reflection with a milky coating, is also being applied. These methods are being transferred to a new photodetector fabrication facility at Argonne to fabricate planar MCP-based photodetectors with highly quantum efficiency bialkali photocathodes. The progress on these methods for photocathode quantum efficiency enhancement will be reported and discussed.

This paper describes a novel HPGe detector, specifically designed to address the challenges of ultimate X-ray spectroscopy and imaging applications. It consists of a multichannel HPGe crystal (monolithic or individual elements) providing excellent X-ray spectroscopy performance. The crystals are cooled using a state-of-the-art electrical cryocooler with active vibration cancellation. The use of a cryocooler does not have any negative impact on the detector performance.

There is a compelling need for a high-frame rate imaging detector with a wide dynamic range, from single x-rays/pixel to > 10⁶ x-rays/pixel, which is capable of operating at both 3rd generation and XFEL sources with sustained fluxes of > 10¹¹ x-rays/pixel/s [1, 2]. The goal of the HDR-PAD project currently under way at Cornell University is to develop such a detector. We hope to utilize the high-density electron-hole plasma created in silicon sensors by the absorption of high intensity pulses to reduce peak photocurrents to levels compatible with processing times of pixel-level electronics.
In order to study the effects of high electron-hole concentrations in silicon sensors we have developed a measurement platform similar to the one used in [3] using optical lasers to emulate the conditions found at XFELs. Characterizations of the employed tunable wavelength laser with picosecond pulse duration have shown Gaussian focal spots with sizes of 6±1 um rms over the relevant spectrum. The available intensity is 2 to 3 orders of magnitude greater than previous measurements presented in [3].
Results from measurements on a typical pixelated diode intended for use with the HDR-PAD (150 um pixel size, 500 um sensor thickness) will be presented showing representative waveforms, the potentially harmful peak currents arising from high intensity illumination, and the effects for individual pixels in comparison with the diode as a whole.

References:
[1] DOE_BES_Detector_Workshop. https://science.energy.gov/~/media/bes/pdf/reports/files/NXD_rpt.pdf
[2] Kramer, D., SLAC x-ray user facility to be updated, again. Physics Today, 2013. 66: p. 21-22.
[3] Becker, J., Signal development in silicon sensors used for radiation detection. PhD Thesis, Department Physik, University of Hamburg, 2010.

The DSSC (DEPFET Sensor with Signal Compression) is a new instrument with non-linear compression of the input signal and with parallel signal processing (filtering, linear amplification, and 8/9-bit digitization) for all pixels. The DSSC will serve as 2d megapixel photon counting detector at the European XFEL (X-ray Free Electron Laser) currently under construction in Hamburg, Germany. The DSSC design goal is to achieve at the same time single photon detection and high dynamic range of about 10⁴ photons, both for photon energies down to 0.5 keV and read-out speeds up to 4.5 MHz. Realization of this goal requires an accurate calibration of the non-linear system characteristic (NLSC) over the full dynamic range of the detector. The NLSC describes the relation between the signal charge collected in a sensor pixel and the respective digital output of the DSSC system, and must be determined for each of the 1024 x 1024 DSSC pixels. We present our strategy for calibrating the NLSC, and report experimental calibrations of the NLSC of a single DSSC prototype pixel for counting 0.5 keV and 1 keV photons. Both calibrations are verified independently with an alternative radioactive X-ray line source, and with an external test bench providing 14-bit resolution.

The DEPFET Sensor with Signal Compression (DSSC) will be a 2d 1Mpx imaging detector for the European X-ray Free Electron Laser facility (XFEL.EU), that is currently under construction in Hamburg. The DSSC is foreseen as a photon counting detector for soft X-ray radiation from 0.5 keV up to 6 keV. Driven by its scientific requirements, the design goals of the detector system are foremost low noise, a high dynamic range and a high frame rate of up to 4.5 MHz. Signal compression, amplification and digitization will be performed in the focal plane. Utilizing an in-pixel active filtering stage and an 8/9-bit ADC, the detector will provide parallel readout of all pixels. A critical step of calibrating the detector is the determination of the system gain and offset based on peak energies of X-ray calibration line sources such as 55Fe. This is demanding due to the intrinsically low spectral resolution of the DSSC. Here the results of studies on the stability and performance of automated procedures for peak fitting in single pixel spectra with a low energy resolution are presented.

FASPAX (Fermi-Argonne Semiconducting Pixel Array X-ray detector) is being developed as a fast integrating area detector with wide dynamic range for time resolved applications at the upgraded Advanced Photon Source (APS). A burst mode detector with intended 13 MHz image rate, FASPAX will also incorporate a novel integration circuit to achieve wide dynamic range, from single photon sensitivity to 105 x-rays/photon/pulse. To achieve these ambitious goals, a novel silicon sensor design is required. This talk will detail early design of the FASPAX sensor. Results from TCAD optimization studies, and characterization of prototype sensors will be presented.

Laser plasma accelerators generate GeV electrons with acceleration distances of a few centimeters. This technology enables compact Thomson scattering photon sources at energies of 1-10 MeV, which have applications in radiography, photo-fission and nuclear resonance fluorescence for nuclear nonproliferation and homeland security. Knowledge of the energy-angle distribution of the photon bunch is crucial to source development as well as to enabling new applications. However, diagnosing Thomson sources is challenging due to the high intensity, ~10⁸ photons per shot, and milli-radian angular divergence. We develop a simulation framework in Geant4 for a diagnostic system composed of a thin scatterer and a scientific CCD electron tracker. The uncertainties introduced by the scatter and the tracker in reconstructing a 1.73 MeV mono-energetic photon sources are evaluated, which determine the intrinsic limit of the current design on measuring the energy-angle distribution. With the flexibility the framework provides, an optimal diagnostic system will be designed.

Coincidence summing is a difficult problem to address in highly efficient HPGe detectors, and this effect is compounded when using a Compton-suppression detector. One approach is to used the known decay schemes of common calibration nuclides to obtain two efficiency curves: one for the full-energy peak and one for the total rate between both detectors. By fitting both curves to the measured count rates and the underlying decay schemes, the efficiencies and any coincidence correction factors are found for all energies. The approach was validated by an additional source which exhibits both summing and non-summing gamma rays.

We developed a gamma camera specifically for use in plant nutrition research, and we used it to successfully obtain images of the uptake and partitioning of Cs-137 in intact plants. The collimator of the gamma camera (acceptance angle: 28°, aperture diameter: 1 mm) was designed for imaging high-energy gamma photons from Cs-137. However, the prototype pinhole collimator causes small artifacts in the acquired images; moreover, the imaging time is quite long with the use of this collimator. To improve the image quality and to increase the sensitivity of the gamma camera, we designed new collimators made of tungsten (0.248 mm^-1), which has one of the highest attenuation coefficients for imaging 662 keV gamma photons. These collimators are manufactured using wire-cut electrical discharge machining. One collimator is similar to a collimator that undergoes edge treatment, and the other has a smaller acceptance angle (13°) than the collimator currently in use, but an identical aperture diameter (1 mm). We will use the latter collimator to make a clustered multi-pinhole collimator. Experiments for evaluating the collimators installed in the gamma camera were performed with point sources of Cs-137 of 1 MBq and 2 MBq. The images obtained indicated an improvement in the FWHM to 7.5% with the new single-hole collimator; a slight cancelation of image artifacts was also observed. The latter pinhole collimator maintains the image quality and sensitivity despite the smaller acceptance angle. The newly manufactured pinhole collimator of the high-resolution gamma camera system is able to achieve high-performance imaging of not only radiocesium, but also radiotracers of plant nutrient element kinetics in a plant body.

In a severe accident of a nuclear power plant, it is important to survey the position of released radioactive material rapidly in order to protect the workers and citizens from radiation exposure. Gamma-ray imaging is an important and useful tool for detection and localization of radioactive material. There are two popular methods to detect the direction of incident radiation, anger camera and Compton camera. The weak point of these conventional methods are the narrow field of view. To overcome this disadvantage, we have proposed a stacked scintillator detector based on the Compton gamma camera. The detector was composed of stacked scintillator bars which ends were connected to photon detectors and each scintillator bar worked individually. The interaction position was derived by the position of the bar and the light output ratio at the ends of the bar scintillator whereas the deposited energy was obtained by summing the two light outputs at the end of the scintillator. A modified Compton reconstruction algorithm was applicable to estimate the direction of incoming gamma-rays. The symmetric geometry of this detector provides a detectable angle for 4-pai direction and the high detection efficiency. An experiment was carried out with a prototype detector which consisted of sixty four Ce:GAGG scintillator bars arranged in 8x8 array with silicon photo-multipliers. A Cs-137 point source was located at 30cm from the center of the scintillator array and detector response was recorded. With these data, back-projection by the modified Compton reconstruction was carried out. Though, a slight shift between right incident angle and reconstructed direction were observed in the cases that the radiation source distributed for phi-direction in polar co-ordinates, a clear peak was observed at correct direction in the reconstructed image. From these experimental results, proposed detector can detect the direction of incident gamma-ray radiation sensitive for 4-pai direction.

In the irradiation room of accelerator facilities, air-dose rate varies from place to place especially just after irradiation. Nevertheless, it is generally monitored at only one place for radiation safety. When we enter the room, we should check the air-dose rates by a survey meter with exposure to radiation. If a remote and multipoint monitoring system is available, we can reduce the risk from radiation exposure. We propose a new webcam-based air-dose rate monitoring system, in which multiple webcams are driven remotely by a single PC. A CMOS image sensor in a webcam can detect not only visible light but also ionizing radiation. Covering the lens with light shield, we can observe radiation events as bright spots on a black background. Since a few MeV charged particles emitted in beta or alpha decays cannot penetrate the package of the CMOS image sensor, only gamma-ray event can be detected. Therefore, we can measure gamma-ray event rates where the webcams are placed. Gamma-ray event rates are well used for conventional measurements of air-dose rates. The event rates in units of cpm should be converted into the air-dose rates in units of µSv/h. The conversion function was determined through calibration measurements using a ¹³⁷Cs standard gamma-ray source, and was implemented into software developed for the measurement of air-dose rates. To demonstrate the webcam-based monitoring system under real radiation environment, we performed the first test experiment with a single webcam at an irradiation room of the Kyushu University Tandem Laboratory. As a result, we confirmed that the temporal variation of the monitored air-dose rate was consistent with that of the beam current measured by a Faraday cup. This test result has encouraged us to develop an air-dose rate monitoring system with plural webcams suitable for multipoint monitoring. Toward practical use, we plan to evaluate the performance using a standard radiation field.

The continuous radiation monitoring is strongly required after the accident in Fukushima Daiichi nuclear power plant. The aerial monitoring is very useful for mapping the dose leve in the wide area. The gamma camera based on Compton imaging for the autonomous unmmanned helicopter has been developed after the accident. The camera consists of 8 by 8 array of GAGG crystals (10 x 10 x 10 mm^3 for absorber, 10 x 10 x 5 mm^3 for scatter) individulally coupled to SiPMs (6 x 6 mm^2 KETEK PM6660). The signals are processed with ToT based readout circuit and data acquisition FPGA. The developed camera shows the energy resolution of 6-7 % and the measured angular resolution is 9.6% (FWHM) with the detection efficiency of 1.6 %. The developed camera was applied to the dose measurement in Namie city of Fukushima, compared with the air dose level measured by a survey meter and confirmed to be useful for mapping the radiation level at the ground.

The performance of a spectrometry system (SPEC) for identification of trace activities in water is presented. The SPEC detector is a part of the TAWARA_RTM platform designed for monitoring of water processed for distribution by the Waterworks Company. The SPEC system is dedicated for identification of radioisotopes emitting γ-rays of energies between 50 keV and 2 MeV. The SPEC detector comprises a CeBr3 scintillator grown from specially purified raw material with reduced content of actinides that produce unwanted alpha particle background. In order to reduce the Compton scattering background, an active anti-Compton shield (ACS) made of BGO is used. In addition, a passive lead shield around the ACS is used for further suppression of the external background. The SPEC detector is designed for use with a dedicated concentrator system, that will be used for absorption of a selected group of radioactive elements that may be present in water processed at the waterworks. The system is tested upon capability to detect the γ ray emitters with activity according to the guidance levels published by the EU in the Council Directive.

Pair production (PP) events are observed with gamma spectrometry when investigated samples emit sufficient numbers of photons with energies greater than 1.022 MeV. Because this condition is not typical of environmental samples, detection of PP is uncommon for environmental radioactivity. Nonetheless, this study experimentally demonstrated the detection of PP for environmental samples of relatively high amounts of the natural, radioactive isotope of potassium 40K, utilizing low background gamma spectrometry with sufficiently long counting times. Such detection was spectrally seen through the escape events of the annihilation photons that typically follow PP. Moreover, this study computationally demonstrated the dependence of these escape events on the density of the detector, and the inverse relationship between these escape events and the detector size. These computational results were found to agree with the theory.

As a part of a joint research project of the National Radiation Protection Institute and the Czech Technical University in Prague a unique testing device MONTE-1 was developed at the training reactor VR-1. The device allows performing an advanced testing of various detection systems of intervening mobile groups in a real gamma radiation field of fission radionuclides that can be encountered in case of nuclear power plant accidents. The real photon field of the fission radionuclides cannot be practically created with the use of commercially available radionuclides. Therefore, uranium fuel elements irradiated in an experimental reactor VR-1 was used to generate the radiation field. CdZnTe and HPGe detectors were chosen for testing and measurements in the fission gamma radiation field. Spectra of the both types of detectors were acquired by means of sequential measurements made several times after the irradiation, covering thus various levels of the gamma radiation field. In spectra, peaks of short-lived radionuclides (e.g. ¹³¹I, ¹³²Te, ¹³⁵I, ¹³⁵Xe) were identified and activities were estimated. This work was supported by the Ministry of the Interior of the Czech Republic within the security research program VG20132015119.

Radioactive materials were released by Fukushima Daiichi nuclear power plant accident, and the decontamination work has been performed widely, mainly in Fukushima prefecture. The gamma-ray camera which can take an image of a radiation intensity distribution at the general environment radiation level (0.05 uSv/h) to support the decontamination work has been needed. The ETCC (Electron Tracking Compton Camera) is the gamma camera that can detect the incident gamma-ray direction and the number of events of gamma ray can be measured quantitatively. The ETCC for environment that can take an image of a low-level environment radiation intensity distribution has been developed. The quantification was achieved by indicating the air dose rate per the unit solid angle on the gamma ray image. The number of total events in FOV which is measured using the ETCC for environment (view angle: 100 degree) was around 50 events for two hours in the 0.1 uSv/h field after decontamination. It's difficult to take an image of a radiation intensity distribution by these small numbers of events. It's very necessary for purpose of the gamma ray image display which can be trusted statistically to accumulate many events by long time. However, the measurement time as short as possible is desired by measurement at a decontamination site. The FOV that has the 100 degree view angle set to one division at the beginning. This one division is subdivided when the event rate is larger than 20 cps. Each division must have more than 10 cps (larger than 3-sigma). The gamma ray image had the high spatial resolution by subdivide divisions when the hot spot existed or the long time measurement. The quantitatively gamma ray image has been taken within 2 hours at the site where the radiation strength was reduced from 0.24 uSv/h to 0.12 uSv/h by the decontamination.

Heavy ion therapy can form fine dose distribution and irradiate only a target organ. Although fine dose distribution can reduce undesired irradiation into normal organs, misalignment of an irradiation position may cause significant accidental exposure and/or deficiency of the irradiation dose into a tumor. In order to accurately estimate the irradiation dose, dosimeters are required to be inserted into an affected region in a patient body. We, therefore, have developed a small size dosimeter consisting of an optical fiber and an optically stimulated luminescence (OSL). This dosimeter can read out OSL signals through the optical fiber when irradiated with a stimulation laser. However, the OSL materials show quenching effect when irradiated with high linear energy transition (LET) particles. In this paper, we discuss the correction of LET dependence of small OSL dosimeters. We fabricated two types of small size dosimeters using different OSL materials, Eu:BaFBr and Ce:CaF₂. Carbon ions were irradiated into the fabricated dosimeters at Heavy Ion Medical Accelerator in Chiba (HIMAC). The small size dosimeters were set behind the water equivalent acrylic phantom. We confirmed the luminescence efficiencies of Eu:BaFBr and Ce:CaF₂ decrease with the LET. The ratio of the luminescence intensities between Eu:BaFBr and Ce:CaF₂ also reduces as a function of the LET. We can obtain the LET value from this relation and then determine the luminescence efficiency of each dosimeter. We, therefore, can correct the LET dependence of the luminescence efficiency.

Increasing CO₂ concentration in the Earth’s atmosphere is driving a search for techniques to reduce the amount of CO₂ being released. Geological carbon storage is one of the methods under investigation to decrease atmospheric CO₂ concentration. Several projects are attempting to make zero-emission coal power plants by capturing the CO₂ from the flue gas and pumping it deep underground in porous rock formations. The monitoring of these underground CO₂ formations to track the displacement of CO₂ is an important undertaking. Multiple methods will likely be required to adequately monitor the reservoirs. One of the methods being pursued is 4-D muon tomography that could detect a 1% change in the reservoir density at a depth of 1-2 km. A borehole muon detector capable of monitoring the muon flux over long periods of time is being developed. Geant4, a Monte Carlo simulation package, has been used to identify an optimal design configuration and generate performance predictions. A bench-top prototype detector is being built to verify the model predictions. The preliminary design is composed of polystyrene scintillating rods with inserted wavelength-shifting fibers connected to silicon photomultipliers to determine energy deposition and incident muon angle. The rods are arranged in alternating layers providing a coordinate system for angular resolution. The detector is being tested both in a laboratory and in the shallow underground laboratory at Pacific Northwest National Laboratory. Analysis methods for the results produced by the electronic readout system have been explored, and the measured data has been compared to simulations to verify the model predictions. The expected performance, design, and initial results will be presented.

The Cosmic Leaving Outdoor Droplets (CLOUD) experiment aims to recreate atmospheric conditions inside a large electro-polished stainless-steel chamber (26.1 m3) in which aerosols, cloud droplets and ice particles can be produced under precisely controlled laboratory conditions and to expose the chamber to an adjustable particle beam at CERN PS, which closely replicates natural cosmic rays. Atmospheric aerosols are any solid or liquid particles suspended in the air. There are many sources of natural and man-made aerosols. Strong winds blow desert dust and sea salt up to higher altitudes. Factories and cars emit black carbon while forest fires are sources of organic carbon. Aerosol affects the Earth's climate directly, by absorbing the Sun's light or reflecting it back into space. Large aerosols (> 100 nm) can act as seeds on which cloud droplets form. The contribution of aerosols and clouds is recognized by the Intergovernmental Panel on Climate Change as the most important source of uncertainty in the current understanding of climate change. The CLOUD experiment aims to settle the question of whether or not they are significantly influenced by cosmic rays. The air injected into the chamber during the experimental runs is produced by a complex gas system designed following the highest standard of cleanliness. During 2015 most of the effort will be concentrated on commissioning the ultra-pure water production module. Water vapour is added to the clean air in order to obtain the desiderate level of humidity in the chamber. The new ultra-pure water production module will allow further reducing the level of uncontrolled contaminants in the chamber. The system for the production of synthetic ultrapure water (directly from burning electrolytically-produced H2 and pure O2) has been completed and preliminary tests have been already carried out in the past years. The present contribution will review the performances of the new water production and humidifier modules in terms of conductivity and total organic Carbon present in the gas stream.

Nondestructive internal inspections with imaging function are quite useful for large structures. Although a transmission X-ray imaging technique has high spatial resolution, it is unsuitable for large size structures because it is necessary to sandwich an object between an X-ray source and detectors. The backscattered X-ray imaging technique can be used for the internal visualization of large size structures because it can inspect from one-side of an object. Conventional backscattered X-ray inspection is conducted by two-dimensionally scanning a relatively low-energy pencil-beam X-ray, in which a rotating collimator is used for one-dimensional scanning. Higher energy X-ray is preferable to take an internal image of a large object because higher energy X-ray has higher penetration ability. However, pencil-beam scanning of high energy X-ray requires a heavy and large rotating collimator for beam shaping and scanning. We, therefore, proposed another approach, in which an X-ray beam is shaped into a fan-beam and a detector is one-dimensional position sensitive, for inspection of large size structures. Our detector has parallel plate collimator perpendicular to the plane of the fan-beam X-ray in order to define X-ray scattering positions. In this technique, we can obtain a one-dimensional backscattered X-ray profile in one measurement. We can conduct two-dimensional imaging by scanning only in one direction. The proposed system requires no heavy rotating collimator. In this paper, we fabricated the prototype detector and conducted basic experiments to confirm the feasibility of the proposed technique. We acquired the backscattered X-ray line profiles from a concrete slab object, when irradiating 950 keV linac X-rays. The acquired line profiles have intense signals corresponding to object positions. As future works, we will make a two dimensional image by scanning in the perpendicular direction to the fan-beam plane.

In many cases when the object consists of low Z plastics and high Z metals, it is very difficult to get good images of both plastic and metal parts from a single X-ray shot. If the X-ray energy is high, a low Z or thin material image is degraded and if the X-ray energy is low, a high Z or thick material image is degraded. Dual shots of two different (a low and a high energy) X-rays with two different detectors optimized to the energies respectively are the ideal solution but it costs not only the complex X-ray equipment preparation but also the doubled test time which is the more important in many companies. Unlike amorphous-silicon X-ray flat panel detectors, a crystal-Silicon CMOS image sensor have a potential to be used for both a direct and an in-direct ionization(scintillation) detector for X-ray imaging. In this study, we present a simple and innovative structure as an X-ray NDT detector, named a stacked CMOS X-ray image sensor (SCXIS). An SCXIS uses two CMOS image sensors and a single scintillator layer.We tested the effectiveness of this structure with an available CMOS image sensor having 12.5 x 12.5 cm² area, 55 um pixel pitch, ~10um depletion width for both top and bottom image sensors. As a result of comparison between conventional and SCXIS system, the low Z material information, such as a PCB plate, is clearly shown in suggested system together with high Z material image but not well in the conventional detector image especially at high energy. In the conference, we will present the full results by the SCXIS structure such as SNR and DQE etc., and images at higher than 100 kVp.

Optically Stimulated Luminescence (OSL) properties of AlN ceramics have been studied. The AlN ceramic plate was manufactured by Tokuyama Corporation (Yamaguchi, Japan). It looks non-transparent and light grey in colour. After the irradiation by X-rays, the detector plate shows a broad emission with the peak around 360 nm when it is stimulated by red LED light (~630 nm). A measurement of the stimulation spectrum unveiled that the OSL is most efficiently stimulated around 800 nm, but it can also be stimulated in a wide range of wavelengths tested from 550 to 900 nm. It suggests that the ionized charges by X-rays have been captured by many number of trapping centres. With this AlN OSL detector, we have confirmed that the measurable dose range range is at least 0.1 - 20 Gy. Here, the measurement of lower dose was limited by the instrumental sensitivity and upper side was limited by the loading capability of X-ray tube used. We believe that with a use of an optimized reader, the lower side of dynamic range will be extended by at least one to two orders of magnitudes. Furthermore, it was found that the OSL signal exhibits relatively long afterglow. The decay curve consists of two exponential decays with the time constants of 0.1 sec and 243.2 sec. We think that it is because some of the de-trapped carriers by stimulation are temporary re-captured by shallow trapping centres (due to most likely defects) so that it takes longer time for the carriers to make it to the luminescent centres, hence eventually emit light.

Recently we have shown that common, commercially available plastic scintillators (PS) can be used for radon (²²²Rn) measurements. They absorb radon in their volume and have different pulse decay times of the signals of alpha- and beta- particles, which allows alpha-/beta- pulse-shape discrimination (PSD). With this approach and using optimal PSD settings we have obtained alpha spectra of radon and its progeny absorbed in PS like BC-400 and EJ-200 with energy resolution better than 6.5%. To the best of our knowledge, the response of plastic scintillators when they are exposed to thoron (²²⁰Rn) has not been studied yet.
The objective of this work is to perform experimental study of the response of plastic scintillators when exposed to air containing thoron or a mixture of radon and thoron. The pulse shape spectra of the scintillators are studied and their alpha-/beta- pulse shape discrimination capabilities are evaluated. The alpha spectra of radon, thoron and radon+thoron absorbed in EJ-200 (and their progeny) are acquired with optimal PSD settings and analyzed.
The results of the study show that plastic scintillators can detect radon and thoron in the environment. Their pulse decay times are different for alpha- and beta- particles, which allows alpha-/beta- pulse shape discrimination. The pulse height spectra obtained after pulse-shape discrimination of the beta- pulses show good energy resolution of the alpha- peaks in the case of radon, and lower energy resolution in the case of thoron. The energy resolution is good enough to allow detection of thoron and its progeny which are absorbed or plated-out on the surface of the PS, regardless of the ambient radon concentration. The measurements of exposed PS with liquid scintillation counters demonstrate the applicability of these counters to activity measurements of ²²²Rn and radon and thoron progenies absorbed in or plated-out on the plastic scintillators.

In the framework of developing instrumentation aimed at measuring radiation quality, a new production of improved silicon microdosimeters based on the Monolithic Silicon Telescope (MST) technology has been recently finalized. Reduced dead layer, high fluence rate capability and better chord length distribution have been obtained thorough modified process and design. Electrical and functional tests have been successfully completed and are presented.

Collection, proper utilization and management of waste in a sustainable way are very important in order to protect the environment. In most of the places around the world, the typical way of waste management is disposal of wastes into dump stations and landfills. These sites produce a number of toxic gases and a large amount of leachate. Leachate is liquid, which washes away or extracts toxic components, minerals and other materials while percolating through wastes. Leachate, then can get mixed with surface water and aquifers under the ground, affecting fresh water resources. Together with many other hazardous materials, Chromium (Cr) can also be found in leachate. Cr, more specifically Cr(VI), is a known carcinogen and may cause lung cancer. In this research work, measurements have been conducted in order to detect Cr in water with various Cr concentrations, using X-ray fluorescence. The measured Ka photon counts from the samples show nearly a linear relation with respect to the increasing Cr concentrations. This method can be used to detect Cr and also, other harmful components in leachate, automatically. The high energy fluorescence photons yielded by other heavy materials in leachate, might influence the signals of interest. In order to construct a proper detection system, this effect should be taken into account.

Neutron sources whose neutrons can be tagged according to their time of emission are extremely useful because time-of-flight spectroscopy can be used to accurately measure their neutron energy spectrum. Sources utilizing the ⁹Be(a,n)¹²C reaction exhibit neutron groups corresponding to the states of the ¹²C residual nucleus. Reactions in which the ¹²C nucleus is left in an excited state are characterized by the emission of an energetic gamma ray in addition to the neutron. These gamma rays were used to tag the fast neutrons emitted from a 1-Ci ²³⁹Pu/⁹Be source and time-of-flight spectroscopy was employed to measure the neutron spectrum from approximately 0.4 MeV to 6.4 MeV.

A method to improve radioactive waste drum activity estimation in Segmented Gamma Scanning (SGS) systems was developed for homogenous content. The method was tested with simulations and a small scale model. Using methods of Beam Forming (BF), taken from Radar spatial signal processing, allows eliminating the use of physical collimator and use a digital filter instead. With this digital spatial filter we search for the radioactive sources within the drum volume. Under the assumption of known homogenous absorbing material, we construct an "Attenuation vector" to translate source activity from every possible position in the drum, to each of the detector sample locations surrounding the drum envelope. From the linear model we derive the Maximum Likelihood Estimator (MLE) of the multiple sources position and activity. We solve this hyper-dimensional search problem using an Alternating Projections (AP) technique. A mathematical simulation was results were compared to the Cramer-Rao Lower Bound (CRLB) theoretical minimum variance. The simulation results are consistent with a small scaled model experiments and showed an improved accuracy with comparison to industrial SGS systems. Our preliminary results indicates that a large improvement in the total activity estimation accuracy is expected, comparing to the commercial systems. Furthermore, since this method eliminates the need for heavy led collimator, the source is not blocked by the collimator for the whole measurement period, which provides the advantage of an increased count rates and decreased total measurement time.

New event-by-event fission models have prompt neutron and gamma-rays that are correlated in time, energy, and multiplicity, however there is limited measurement data available to validate these models. Measurement of high-order fission neutron and gamma-ray coincidences is difficult and there has previously been little motivation to measure properties of both particle types simultaneously. High-order Cf-252 spontaneous fission neutron and gamma-ray coincidences were measured with an array of 24 liquid organic and eight sodium iodide scintillation detectors. Measured coincidence data including neutron time-of-flight energy and measured gamma-ray pulse height distributions are compared with MCNPX-PoliMi simulation results from built-in and event-by-event fission models.

A novel backscatter radiography scanning system has been developed for the inspection of railroad wood crossties. Quantitative assessment of image quality is an important consideration in any imaging system and is most commonly described by the Modulation Transfer Function (MTF). In the push-broom scanning method, an additional component of blur caused by system motion can be significant along the direction of travel. In routine quality assurance applications, the bar-pattern method is regarded as the most appropriate technique for evaluating the system MTF. A custom bar-pattern target was constructed for the unique backscatter system, composed of lead line-pairs, which simulate ten discrete spatial frequencies. The test tool was scanned using four different scanning speeds, and the results from each speed were assessed and compared. Results indicate that blur introduced by source motion is most severe for the highest operating speed of 24 km/h, which is capable of resolving details as small as 1.7 cm.

A new type of polymeric biosensors is based on etched nuclear tracks with a certain spatial (typically conical or funnel) forms. The biosensors work properly if the shape of the pores has structural parameters that allow rectification of the pores in ionic media. Wet etching of the ion-irradiated polymers is, however, a stochastic process that may result in non-uniform pore shape distribution, i.e., worsening of the quality of the biosensors. The diagnostic of the 3D pore shapes is a difficult task, most of the methods (e.g., SEM, AFM, SANS, SAXS) are indirect, giving only partial information about the pore shape. In the NPI and IEAP, 2 new nondestructive methods have been developed that allow imaging of the pore shapes in their full 3D forms. The first method is based on combination of the 1D Neutron Depth Profiling (NDP) with the 2D neutron radiography utilizing multipixel detectors (Medipix or TimePix) and Li (or B) decoration markers, the second method is based on analysis of the energy loss of ions from milli- or micro-probe beams. These techniques were proved to be a proper instrument for the inspection of the structural parameters of individual pores of biosensors.

Muon radiography is a promising method to identify massive objects remotely without a need of direct access. Such a method be effective to investigate the status of fuel debris in Fukushima Daiichi nuclear plants. We have constructed muon radiography systems based on 1 cm wide scintillator bars and investigated the status of the Unit-1 reactor, concluding that large portion of the fuel material does not exist in the original fuel loading zone. The muon radiography is limited in investigating lower elevation angle structures. Since the fuel debris has probably dropped to a level similar to the ground level of the detector, locating the detector underground is a unique solution to further investigate the status of the debris. We have carried out a series of measurements to image the iron blocks on the surface while the detector was located underground. The size of the iron blocks was typically 2 m cubic with the detector viewing them through soil thicknesses of 8.5 m (near configuration) and 21 m (far configuration). The lateral yield distribution of muons was normalized by the distribution taken on the surface (image of the sky) to correct for the detector acceptance and azimuthal angle dependence of muon flux. Such 2D images are evident in observing the iron block through the soil of corresponding thicknesses. The absorption by the soil is measured as a function of the average path length in the soil. The normalized yield as a function of the soil density length, the soil density being assumed to 1.5 g/cm³, is used to calculate the mass attenuation length µ_m, resulting µ_m=(1.12 ± 0.05) × 10^-5 m²/kg. Then, the attenuation length in the iron block was calculated similarly. The obtained attenuation length in the iron block was used to estimate the density based on the mass attenuation length. The estimated densities are consistent with the iron density both for the near and far configurations, demonstrating the ability of the muon radiography system located underground to identify the on-surface objects.

For the quantitative measurements of radioactive sources, commonly used well shaped gamma counter and dose calibrator have several limitations of measurement space and radioisotope sample size. Here we designed polyhedral-shaped counter that consists of small detectors at the corners of polyhedral frame. By placing several independent small detectors on the 4pi direction of the radioactive source, the wide polyhedral-shaped inner detection space was expected to lower the measurement error as to well-shaped counter. To investigate the distribution of measurement error in the polyhedral-shaped detection area; we calculated the incident radiation on detector surface using solid angle variation. Based on this solid angle calculation, we determined the 25×25×25 cm³ cube-shaped counter, which consists of Hamamatsu Si PIN diodes with amplifier board, and 8-channel cortex-M3 micro controller. We measured the count rates using F-18(180 mCi) solution contained in the vial at 21 different position. The measuring area was the circle of 15 cm diameter on the center of cube(calculated deviation is about <3%). The errors were calculated by comparing the count rate at the center and the other positions. The mean of errors showed a very low value as 1.17%. In this study, we verified that the polyhedral-shaped counter has the possible to quantitatively measure the radiation of a wide space. Although we used PIN-diode which has low detection efficiency for gamma ray, if high efficiency detectors such as scintillation detector are used, polyhedral-shaped counter is expected to be applied to various radiation measuring devices and region monitoring system.

Gamma tomography has been used to inspect the crack, blockage and internal fluid flow in pipes. A dual-energy gamma tomography (GT) system has the potential to improve the inspection accuracy of the hold-up distribution through observing gas/fluid or water/oil flow patterns independently. GATE (Geant4 Application for Tomographic Emission) was used to evaluate the system performances of the dual-energy GT. The dual-energy GT consists of the 40-degrees fanbeam-shaped Ir-192(317, 468keV) and Cs-137(662keV) sources and six CsI (Tl) detectors with 2 cm thickness and 8 cm diameter. The distance between the source and detectors is 80 cm. An iron pipe having air, water and oil mixtures in it is modeled as a phantom. 36 equally spaced projections spanning 180 degrees were acquired and a cross sectional image was reconstructed using Filtered Back-projection (FBP) algorithm. The hold-up distribution in a pipe could be investigated using a dual-energy subtraction technique.

By the Fukushima accident on March 11th 2011 in Japan, fuel debris was generated inside the Fukushima nuclear facilities. The imaging of the fuel debris is difficult because of large amounts of background radiation. For suppression of background, we focused on coincidence detection of double photon emission nuclides existing in the surrounding structure materials of fuel debris and fission products. Those nuclides such as ⁶⁰Co or ¹³⁴Cs generate two photons at the almost same time. They can be distinguished by coincidence detection of the two photons. We are developing 3-D Compton Imaging system for the double photon emission nuclides. Compton imaging has some advantages especially for high-energy gamma ray in terms of non-necessity of mechanical collimation. In this paper, we installed 8x8 pixelated GAGG and SiPM arrays for detectors and dynamic Time over Threshold (dToT) method for A/D converter [1]. In the current situation, the single photon Compton imaging system showed 12.96 degrees of angular resolution for ¹³⁷Cs. The reconstruction algorithm can be improved for 3-D imaging in the future.

To fulfill the demand of special nuclear materials detection in the homeland security, the nuclides identification technique with photoneutron resonance technique is researched at Tsinghua University. Photoneutrons are produced by the X-rays of a high energy e-LINAC with a heavy water photon-to-neutron convertor. The size and shape of the convertor are designed to strike the compromise among the parameters of neutron yield, neutron spectrum and emission time variance of neutrons from the target. A boron loaded liquid scintillator detector is used to moderate and measure neutrons within the energy range of [0.1eV, 100eV]. Neutron spectra are measured via the time-of-flight method, with the distance of 4.67 meter from the neutron source to detector. The intrinsic detection efficiency is better than 50% and the energy resolution is less than 30%. Eight kinds of different materials (Ag, Sb, Nd, Tb, Ho, Er, Ta, W) are used as the simulants to test the capability of nuclides identification. An algorithm is also researched to identify nuclides and their concentrations. The experimental results confirm the capability of nuclides identification and show that the photoneutron resonance technique is promising to find and analyze the concealed special nuclear materials.

Mass accountancy measurement is a nuclear nonproliferation application which utilizes coincidence and multiplicity counters to verify special nuclear material declarations. With a well-designed and efficient detector system, several relevant parameters of the material can be verified simultaneously. 6LiF/ZnS scintillating sheets may be used for this purpose due to a combination of high efficiency and short die-away times in systems designed with this material, but involve choices of detector geometry and exact material composition (e.g., the addition of Ni-quenching in the material) that must be optimized for the application. Multiplicity counting for verification of declared nuclear fuel mass involves neutron detection in conditions where several neutrons arrive in a short time window, with confounding gamma rays. This paper considers coincidence-based Pulse-Shape Discrimination (PSD) techniques developed to work under conditions of high pileup, and the performance of these algorithms with different detection materials. Simulated and real data from modern LiF/ZnS scintillator systems are evaluated with these techniques and the relationship between the performance under pileup and material characteristics (e.g., neutron peak width and total light collection efficiency) are determined, to allow for an optimal choice of detector and material.

Effective atomic number (Zeff) is a hypothetical quantity to show the X-ray attenuation by compound and mixture materials. With the measurement of Zeff in a subject, more detailed information inside a subject is obtained than linear attenuation coefficient. Generally, Zeff can be estimated by computed tomography (CT) with using monochromatic X-rays with different energies. The monochromatic X-rays are, however, only available at synchrotron facilities, but not in hospitals, airports and industrial companies. For the measurement of Zeff for the detection of drugs and explosives, energy-resolved CT can be employed. The authors invented a new X-ray detection system, called a “transXend” detector which measures X-rays as electric current and gives energy distribution of incident X-rays after analysis. With previously measured response functions, X-ray energy distribution is unfolded. The number of analyzed energy ranges and the widths of energy ranges can be defined according to the materials to measure. With defining two energy ranges as narrow as 1 keV, the X-rays in these energy ranges are recognized as quasi-monochromatic. In the previous study, we measured the Zeff of acrylic (6.47) and aluminum (13). The numbers in parenthesis show theoretical Zeff. This study shows the measurement results of smaller Zeff with simulating materials of drugs and explosives. Employed specimens are four plastics: polypropylene (PP) (5.44), ABS resin (ABS) (5.76), polycarbonate (PC) (6.26) and polyvinylidene difluoride (PVDF) (7.88). Measured results show good agreement of 3~5 % for PC and PVDF. For smaller Zeff, i.e., PP and ABS, the agreement with theoretical values are rather poor, 11~18 %. Analysis improvement is under study.

The PINS Chemical Assay System is a field-portable Prompt Gamma-ray Neutron Activation Analysis (PGNAA) system. [1] For over 20 years, the U.S. military has used the PINS to nondestructively identify the fill chemical inside thousands of suspect chemical warfare munitions. First- and second-generation PINS systems use a 252Cf neutron source to induce capture reactions and inelastic-scattering reactions in the object under test. Currently, we are testing two third-generation PINS systems, using neutron generators in lieu of a 252Cf radioisotopic source, to simplify PINS shipping and storage logistics. Our test results will provide a firm design basis for future PGNAA nondestructive evaluation systems for chemical warfare agents and explosives. One neutron generator employs the deuterium-deuterium (DD) nuclear fusion reaction to produce monoenergetic 2.5-MeV neutrons, and the other uses the deuterium-tritium (DT) reaction to create monoenergetic 14.1-MeV neutrons. In contrast, 252Cf fission produces a broad Maxwellian distribution of neutron energies, with a mean of 2.1 MeV and a characteristic temperature of 1.4 MeV. [2] The 14.1-MeV neutrons from a DT generator permit the excitation of carbon and oxygen inelastic gamma rays, greatly improving PGNAA identification of the World War I-era chemical warfare agent phosgene. In general the more energetic neutrons from the generators produce more gamma rays from neutron inelastic scattering reactions than californium neutrons, but fewer gamma rays from neutron-capture reactions. Our tests are being performed with actual and simulated chemical warfare agents, an explosive, practice-fill chemicals, and smoke generating chemicals—all found in the “old and abandoned” munitions that have lost their identifying marking due to corrosion over the years. To our knowledge, this is the first test directly comparing the gamma-ray response of live-chemical warfare agents to neutrons from a 252Cf source, a DD neutron generator, and a DT neutron generator.

The ability to detect radiological threat sources using gamma-ray detection in an urban search scenario is complicated by the large variation of natural radioactive backgrounds, large stand-off distances, cluttered environments, and the presence of benign sources. To varying degrees, detection probability may be improved and false alarm rates reduced, through increased detector efficiency (number), improved detector resolution, and utilization of advanced algorithms. We study the effect of these parameters on detection probability using data collected by the Radiological Multi-sensor Analysis Platform (RadMAP), a truck loaded with 100 NaI detectors and 24 HPGe detectors. The data set used in our analysis was collected with the NaI and HPGe systems over three months in urban, sub-urban, and rural environments around the San Francisco Bay Area and separated into two sets for training and testing two distinct detection algorithms. In our analysis we compare a trained region-of-interest (ROI) detection algorithm with the Poisson Clutter Split (PCS) algorithm from Physical Sciences Inc. Source injection studies were used to characterize detection performance of the two algorithms against sources of ¹³⁷Cs and ¹³³Ba for activities ranging from 5--300 µCi and for varying number of detectors. Using this unique data set, we have performed a quantitative analysis of how trade-offs in detector array size and energy resolution impact the detection sensitivity that may be achieved when using both standard and advanced detection algorithms. We find that PCS significantly outperforms ROI for both source isotopes and that the relative impact of energy resolution and detector efficiency on overall performance is highly dependent on the choice of algorithm.

The Random Forest supervised classification algorithm was applied to a source injection dataset taken from the Large Area Imager, a mobile gamma ray coded aperture system developed at Oak Ridge National Laboratory. Geant4 simulations of weapons-grade plutonium were combined with background data measured by the physical system to train a classifier and evaluate its performance. The measured background data was processed as though the system maintained a constant speed throughout its cross-country journey. Under this assumption, nearly 4000 1-D coded aperture images spanning approximately 800 kilometers were reconstructed for the study. Out of bag estimates from training indicate that the Random Forest classifier was able to detect the simulated threat source with error rates as low as 0.65% at a moderate standoff distance without spectroscopic information. With the addition of an image-processing step, a 0.2% error rate was achieved. It was further demonstrated that background subtraction using learned PCA (principal component analysis) features substantially increased a figure of merit for detection when using a single feature.

Abstract In homeland security and nuclear safeguards applications, non-destructive techniques to identify and quantify special nuclear materials are in great demand. Although nuclear materials naturally emit characteristic radiation (e.g. ?-rays, neutrons), their intensities and energies are normally low. Furthermore, such radiation could be buried in large background and intentionally shielded with ease. For example, in used nuclear fuel assay, input ?-rays count rate could easily reach 106 cps or higher even after cooling for a few years. The counts are dominated by background radiation from long-lived isotopes. Active interrogation technique based on photofission has been identified as an effective assay approach. In system design based on such technique, nuclear data, such as fission product yields, plays a crucial role. Although fission yields for neutron-induced fission have been available in various nuclear databases, published data on photofission product yields is rare. This poses a great challenge in the application of this technique. In this work, fission product yields of U-238 and Pu-239 after photofission were measured based on delayed gamma spectra. The experimental outcomes were then compared with MCNPX simulation results. This comparison demonstrated the capabilities and limits of current MCNPX simulation package. Keywords: photofission; product yields; MCNPX;

Abstract—The energy dispersive x-ray diffraction (EDXRD) is a novel identification technique suited to security screening. It has been used to detect illicit substances, such as explosives and narcotics, which are mostly polycrystalline. Because of the internal molecular order, liquid substances also produce characteristic diffraction spectra. Features could be extracted from the EDXRD spectra, and we could use them to distinguish liquids. In order to test the detection effect of liquid substances with EDXRD, a test bed facility is set up. 38 kinds of liquid samples, illicit substances and daily supplies, are measured in this study. Some contrast tests are done between traditional CT and EDXRD, in order to show EDXRD’s advantages towards the traditional CT in the identification of different liquids. Other experiments on ethanol with different concentration are conducted under the same irradiation condition. It is shown that the main peak position of the XRD spectrum depends on the concentration f of the ethanol. Conversely, f may be derived from measurement of the peak position. The main peak position of the liquid’s XRD spectrum is useful for security screening. With the limited scope of this study, EDXRD proves to have excellent potential for liquid security screening.

The search and identification of radioactive sources using man-portable radiation detectors is an essential part of the mission carried out by first responders, law enforcement and military personnel. Current approaches use ad-hoc techniques based on the experiences and training of individual users and suffer from low repeatability and long localization times. A systematic approach can significantly enhance the search capability by implementing the best search practices aided by processing algorithms embedded on ubiquitous mobile computing devices. In this paper we report the performance results of IDtector™ hand-held radiation detection system developed by Physical Sciences Inc. (PSI). The system combines real-time (1 Hz) threat detection and isotope identification with advanced search techniques for source localization in a compact and flexible package. The system is evaluated in the context of a wide-area search for a radioactive source. The use of PSI’s Poisson Clutter Split (PCS) algorithm implemented on the system results in detection and simultaneous identification of a nominal 1 mCi source from 15 m stand-off range, while operating at a mission relevant false warning rate of 1 in 4 hrs. Source localization is facilitated by a Spin-to-Locate (STL) technique which uses shielding by operator’s body to modulate the radiation flux and estimate source azimuth. STL can be employed immediately following detection and results in < 7º RMS error of azimuth estimation.

A robust network of distributed sensors is being designed and developed to detect, track, and identify potential threatening radiation sources in moving vehicles without interrupting the flow of traffic in typical highway scenarios with high confidence and very low false alarm rate. The system is being developed as part of an Advanced Technology Demonstration (ATD) program sponsored by the US Department of Homeland Security, Domestic Nuclear Detection Office (DHS/DNDO). The algorithmic basis for the system depends on a number of data fusion methodologies to optimally combine and exploit multi-sensor, multi-modal data. Specifically, data-level fusion of radiation measurements is being used to enhance detection and identification of radiation sources, while extracted feature-level data from auxiliary video sensors is used both to improve computational speed and accuracy as well as provide operationally relevant source attribution information. An overview of the current development work will be provided in two parts: 1) A theoretical description of the data fusion algorithms and their expected utility will be provided; and 2) Performance results from both simulated and real measurements will be used to demonstrate the efficacy of a system using the proposed data fusion algorithms. The expected value of the testbed system using the advanced algorithms will also be discussed. This work has been supported by the US Department of Homeland Security, Domestic Nuclear Detection Office, under competitively awarded contracts HSHQDC-13-C-B0034 and HSHQDC-14-C-B0049. This support does not constitute an express or implied endorsement on the part of the Government.

Hybrid system of L-edge densitometer and X-ray fluorescence spectrometry (XRF) is one of the instruments of on-site safeguards at nuclear facilities. Hybrid L-edge/XRF is an instrument of determination of nuclear material concentrations as transmission and reflection of continuous X-ray energy beams across nuclear material solution sample for safeguards. The system was designed for portable and compact type from advantage of using low energy X-ray beams without heavy shielding systems and liquid nitrogen cooling compared to K-edge/XRF densitometer. In this study, the system is designed using Monte Carlo method considering geometry, shielding, and physics for determination of concentration of uranium and minor actinides. The analysis of uranium concentration and minor actinides was considered by combination of linear extrapolation fitting from jump at L-edge of the nuclear material and the peak ratio of uranium to minor actinide from XRF measurement. In order to maximize the efficiency, the angle of detector for XRF was not only simulated but the collimator geometry was considered. Following simulation and analysis, the concentration of uranium and minor actinides could be estimated a given liquid nuclear material sample.

Abstract: The detection of unregulated radiological sources on a global scale is challenged by the unavailability of economical sensors that meet minimum required performance metrics. The performance of current gamma-ray sensors are all limited in one or more desirable traits, such as detection efficiency, energy resolution, linearity, room temperature operation, and cost of production. A new promising scintillator, KSr¬2I5:Eu, under development at the University of Tennessee, has achieved an energy resolution of 2.4% at 662 keV at room temperature at growth rates much higher than similarly performing scintillators. The detection capabilities of this scintillator, related to the DNDO mission, have yet to be characterized which is the purpose of this work. In order to gain a quantitative understanding of the detection capabilities of this scintillator a large data set of background sources, geometries seen in a portal monitoring system, and shielded and unshielded sources were constructed with the use of MCNP6. These geometries, background sources, and unregulated sources were then used to find the optimum detection method. Methods of detection that were considered included: gross counts, count rates as a function of source position, and spectroscopic information.

Studies to find an effective nondestructive analysis (NDA) method which can quickly provide information on uranium enrichment classification for safeguards inspectors are rapidly expanding due to an increase in demand and improvement in gamma spectroscopy technologies. Therefore, the present authors have designed and built a quad-CdZnTe (CZT) array with the purpose of on site, fast uranium enrichment screening. The purpose of this design is to: 1) rapidly analyse uranium enrichment from a suspicious sample; 2) easily transfer a portable gamma field case to any inspection points; 3) maximize detector efficiency. A CZT was selected due to better resolution and simpler experimental setups than a NaI and HPGe, respectively. Various sizes and configurations of CZT detectors were simulated and tested. To avoid interference from background radiation, the thickness of a lead collimator was optimized. A new portable gamma spectrometry system utilizing the quad-CZT array was built based on the desired design parameters. It consists of four CZT detectors, a lead (Pb) collimator, and electronics such as a multichannel analyzer, battery, and cables. Four CZT detectors are daisy-chained together and work as a single detector. Considering portability and mobility, all components are placed in a field case (H23.5 x W51 x L38 cm). The total weight of the system, including all components and field case, is 28 kg. In order to operate this system and analyze the output signals, a simple user interface and operating program was developed. The output signals from the CZT array are delivered to the personal computer through a USB port for display and analysis. Performance tests were conducted with different enriched uranium samples to build a database. The experimental results showed that there is much potential for this new portable gamma spectrometry system, based on a quad-CZT array, to quickly provide information on uranium enrichment classification.

Radioactive isotopes of xenon are key radionuclides to be monitored in case of nuclear emergency and for control of the Nuclear Non-Proliferation Treaty and the Comprehensive Nuclear Test-Ban Treaty. In case of nuclear emergency the concentrations of radioxenon in the close vicinity of the nuclear event are high and can exceed the dynamic range of radioxenon monitors, as it was observed after Fukushima Dai-ichi accident. Some organics have high absorption ability for noble gases. We explored the feasibility of such organics to serve as samples to measure radioxenon. Experiments were organized in which samples of salo (fatback), butter, cosmetic and medical greasy creams and pieces of DVDs were exposed to 131mXe concentration of 700 kBq m-3. Additional exposure to 222Rn at similar concentration was made to study whether 222Rn can be a proper surrogate for extensive laboratory studies needed to develop this method for practical application. The specimens were measured by liquid scintillation counting. The results showed that the signal from all specimens is well above the detection limits and remains quantitatively measurable even when the samples are taken for analysis with sufficient delay (up to 30 h) after the end of exposure. The other conclusion is that the desorption properties of samples exposed to 222Rn are similar to that exposed to 131mXe and therefore, 222Rn can be considered as proper radioxenon surrogate for laboratory studies on the method.

A novel analytical back projection Compton imaging algorithm has been developed to run on low-powered devices and allow real time imaging to be conducted. It is shown to give an intrinsic spatial resolution of 1.15 degrees. The algorithm works by reducing the complex 3d imaging space into a 2d image. A secondary effect of this algorithm is that the 2d images enable spatially gated and background subtracted total energy spectra to be easily produced. The speed of the algorithm also enables multiple Compton images to be produced in a short time and so calibration of a Compton camera’s sensitivity across its field of view can be quickly assessed. These sensitivity maps have been used to calculate source activities from Compton camera images. This paper presents details of the algorithm and examples of reconstructed Compton images, spatially gated total energy spectra, background subtracted spectra and calculation of sensitivity as a function of position across a camera’s field of view.

Radiation analysis techniques are used in both the mining and recycling industries to deliver elemental and mineralogical information for process optimization and metal accounting. However, the quality of an ore body, and the composition of scrap metal, can vary extensively leading to significant variation in the quality of material on a conveyor at any point in time. Accurate, real-time analysis can reduce costs, and enhance plant recovery through improved characterization of material delivered to, or handled within, a processing or recycling plant. Common techniques used for online material analysis include X-ray fluorescence, X-ray transmission, and neutron gamma analysis. However, these techniques suffer from low statistical accuracy and sample representivity. X-ray transmission systems traditionally use a broad spectrum X-ray generator to illuminate the sample. A detector array on the opposite side of the item is used to measure the intensity of X-ray flux passing through the items. More advanced systems perform coarse material differentiation using dual-energy X-ray absorption analysis. However, neither of these approaches enables accurate classification of material that is similar in nature. We detail the application of photon counting, energy resolved transmission spectroscopy to massively multichannel on-belt applications in the resource, recycling and aviation security industries. Enabled by very high rate, low dead-time pulse processing electronics we demonstrate the separation of metal and organic material that are very close in effective atomic number. By including the very latest model-based pulse processing technology, and communications architecture, each individual detector channel can process more than 4 million c/s and transfer 1,024-channel energy histograms at a rate of more than 1 KHz. In the largest system delivered to date, data from a detector array over 7 linear meters was processed with 3,996 channels of simultaneous processing.

For a baggage inspection, multiple-detector helical CT scanning technology has been deployed. In a helical CT, the detector array and the x-ray source are rotating continuously in a gantry with the slip-ring technology. With the slip-ring technology, an elaborate x-ray cable and drum system can be eliminated but may increase the production cost and instability of the system. For obtaining three dimensional images from a single rotation, cone-shaped x-ray beam geometry that covers a flat panel detector (FPD) has been developed; it is known as the cone-beam CT (CBCT) system. In many circumstances, one needs a large field-of-view (FOV) to cover the object without data truncation; the idea of using FPD in a half-fan geometry and image reconstruction thereof have been developed to meet the large FOV requirement. In the x-ray baggage inspection, an object support size can be as large as 30 cm in terms of FOV radius. The resulting FOV would be less than the required one even in a half-fan geometry with commercialized FPD. In this work, considering the dead space surrounding the active area of a packaged FPD, we proposed an asymmetrically jointed two FPD-based CBCT scanning protocol in a half-fan geometry and demonstrated its feasibility in a numerical study. We modified the conventional FBP algorithm to accommodate such separated data for image reconstruction. The algorithm has been tested by use of a numerical cylinder phantom that has four smaller cylinders inside. The image from the acquired truncated data in the numerical study was reconstructed successfully. Compared to the image from full data, the images from the truncated data suffered a little bit of high frequency noisy artefact near the boundaries of the object. Using two conventional FPDs, we have shown that an extra-large FOV can be implemented in a CBCT geometry. The proposed system is believed to be promising in a number of industrial applications.

Experimental and modelling research has been performed, focusing on the detection of air fluorescence, associated with alpha particle interactions with atmospheric molecules, in non-specific lighting conditions. The experimental system made use of ultra violet (UV) light emitting diodes (LEDs) as an accurate proxy for a variety of radiation source activities. Results are shown from a bespoke filtering system developed to isolate radiological or nuclear (RN) induced nitrogen emission wavelengths with the intent for daylight operation. A first principles computational model, developed in Geant4, calculated the fluorescence yield for a range of alpha sources. An estimate was found for the fluorescent yield of all the emissions of molecular nitrogen with wavelengths in the 260 - 720 nm range. Temperature, pressure and humidity factors were included within the model. The effect of humidity was found to be small but not negligible and scalable with the primary particle energy. Comments are included on the validation of experimental results against modelled predictions, including datasets collected under solar illumination. This project seeks to increase the current understanding of air fluorescence detection in contamination applications. © British Crown Owned Copyright 2015/AWE

Radiation detection has long been of fundamental interest in a wide range of areas such as nuclear forensics and the environmental awareness of radioactive materials. For example, the Fukushima nuclear accident stimulated citizen scientists to collect and share radiation data across the world. However, it is non-trivial to estimate exact radiation levels using volunteered geographic information (VGI) data due to the spatial and temporal granularity of measurements as well as unprecedented levels of data volume. In addition, the accurate background measurements are unavailable in all areas. This research provides an alternative to understand radiation level changes using graph comparison. Previous work has used sensor networks to detect and track radiation. While this approach uses static sensor networks, mobile sensor networks have obvious benefit to track illicit radioactive materials. However, all previous approaches use the predefined structure of the sensor networks. They might also know or calculate the background radiation levels. The aim of this paper is to understand radiation level changes without having such details. We assume that the region of high dose rates in an environment like Fukushima continues over time, irrespective of the background. Thus the structural similarity of radiation levels based on radiation interpolation maps will reveal the changes of radiation levels

The biggest advantage for adopting RMC approach, compared to Compton imaging or coded aperture approach lies on the unnecessariness of the position-sensitive radiation detectors, which often involve complicated fabrication processes in their production stage, as well as the complication in the electronics and signal processing stage, thus limits their viability and versatility. As an attempt to develop radiation-detection-based technology for the nuclear safeguard and treaty verification application, we build a fast and precise gamma-ray/neutron dual imager. Considering typical challenges in nuclear safeguards and security applications, a dual-mode imager can be very effective tool which can compensate drawbacks of radiation imagers that is based on the detection of only one type of particles. The RMC approach was thus utilized to quickly obtain a statistical pattern on the spatial distribution and the shape of the source. As a first step to develop the technique, a PSD-capable scintillator was modeled, and it was thus simulated for the dual-mode operation by MCNP6 and MCNPX-Polimi Codes. Nominal modulation curves for the combined source of neutron/gamma-ray were calculated varying parameters of the simulation. The influence on the response pattern, associated with the shielding effect determined by the mask design was investigated and the mask design was optimized in order to maximize the shielding effect. We developed the imaging algorithm based on maximum likelihood expectation maximization (MLEM) algorithm. The nominal modulation curves calculated by the Monte Carlo simulation codes were used as inputs for the imaging algorithms to reconstruct the spatial distribution of the source. The preliminary results of the simulated/reconstructed radiation image will be presented at the conference.

Defence Research and Development Canada has developed a low cost system to localise radiation sources and to differentiate them from extended contamination hazards. The system is called PACK (Point vs Area of Contamination Kit) and is designed to be used on a mobile platform. PACK integrates four directional radiation detectors (RadCompass from BTI) with other sensors for geospatial navigation, resulting in a low cost, simple, and robust system. Each RadCompass sensor is partially shielded using tungsten plates to limit its field of view, and each oriented to cover different directions. All of the sensor data is collected, fused and analysed in real-time using a miniaturised processing unit. Multiple computer models were developed to allow the simulation of various scenarios and system configurations. Live experiments with real radiation sources provided a higher level of validation of these simulations. The localisation algorithm utilises the four radiation sensor readings to determine the most probable source position. This capability was first tested using a simple Point Of Closest Approach (POCA) algorithm, which was later replaced by a Maximum Likelihood (ML) algorithm based on a bearing probability density function. The hazard type determination is accomplished by comparing the relative signal strength between the RadCompass sensors.

Isotope identification algorithms for handheld radio-isotope identifiers (RIIDs) have demonstrated a poor performance at automated identification. It is possible to improve identifications using a naï¿½ve Bayesian classifier for automated isotope identification that can deal with the challenges faced by handheld RIIDs. Performance of this method is presented on a large set of test spectra, including spectra measured from special nuclear material and other isotopes of interest.

There is a continuing need to improve the field analysis of radioactive analytes. The Field Alpha Spectrometry Tool (FaST) is a system designed do just that. It enables the rapid field screening and analysis of samples containing alpha emitting radionuclides. The system consists of two major components; the first is a Polymer Ligand Film (PLF) that enables rapid sample processing of an analyte in solid or liquid form into a planar form that is amenable to counting in an alpha spectrometer. The second part of the FaST system is an instrument designed for rapid, field-based measuring of alpha-decaying species. The instrument was constructed entirely from commercial components, and included an embedded touch screen interface developed within the Android operating system. The interface allows users to view and export spectra, calibrate the system, and set up custom regions of interest. The instrument is designed to be operated by non-specialists and has a simple user interface. Water, soil, and fused debris samples were successfully prepared and measured. Each of the samples was prepared from raw matrix material and measured with both the FaST system and a benchtop laboratory reference system. Testing was successfully carried out under laboratory settings and under relevant environmental conditions. Adjustments to the system hardware led to an improvement in energy resolution from ~4% FWHM to better than 1.5% in most cases. However, there is still some room for improvement as the laboratory system reached ~0.8% FWHM when measuring PLF samples.

This paper presents a mathematical framework to describe fission chain propagation induced by a 14 MeV interrogation source, which can be used to determine the multiplication of a subcritical fissile assembly. The technique assumes a one energy group point reactor and builds from the Böhnel equation, using the probability generating function as the primary mathematical foundation. These assumptions sacrifice accuracy for simplicity, but work well for small subcritical objects that better satisfy the assumptions of a point reactor. The characterization of subcritical fissile assemblies has applications in a variety of nuclear security fields. This technique is especially applicable to the characterization of HEU assemblies, since the low spontaneous fission rate in HEU leads to excessively long passive multiplicity measurement times. Additionally, the use of the associated particle method with fast scintillation detectors allows for the prompt fission neutrons to be counted with low background rates, due to the use of a small time window to detect the correlated events. The fast scintillators also detect gamma radiation, which could give useful fission chain signatures.
This paper focuses on the point kinetics model for determining multiplication via 14 MeV active interrogation measurements. There is a short overview of the passive framework, starting from the Böhnel equation and building to the active interrogation framework that is the focus of this work. The model is compared to both simulation and measurement. The probabilities and moments of the fission chain multiplicity distribution predicted by the new framework show good agreement with Monte Carlo calculations. The framework also estimates, to within two percent error, the multiplication of enriched and depleted uranium castings using data from coincidence measurements and nuclear data as inputs.

Nuclear technologies are widely used for energy generation, in research and industry. Safe control of nuclear systems is vital. To address the need for remote sensing of radiation and monitoring, the system based on unmanned aerial vehicles (UAV) was designed. Technical approach to monitoring is to employ a swarm of low-cost, small-scale UAVs equipped with navigational and sensing capabilities to perform the radiation surveillance in potentially radioactive locations, which allows the measurements to be dynamically tracked and mapped. Compact CLYC detector equipped with a digital data analysis system was developed for simultaneous gamma-ray spectroscopy and neutron measurements. Pulse shape discrimination was used to segregate neutron and photon signatures. The detector was integrated into the UAV via its communication and power interface enabling transmission of radiation, time and position data to a ground station via the 900-MHz telemetry radio. The monitoring data could be used for further analysis and prognostics in temporal and space domains. Moreover, based on the cooperative sensing algorithms, the swarm of UAVs can be programmed to search for unattended radiation sources. Maximum likelihood estimation (MLE) technique was utilized to locate the position of a radiation source based signal intensities measured in three or more locations by a single UAV, or simultaneously and cooperatively by multiple quadcopters.

We investigate the utility of coded aperture (CA) for roadside radiation threat detection applications. With coded aperture, information in the form of photon quantity is traded for directional information. Whether and in what scenarios this trade-off is beneficial is the focus of this study. We quantify the impact of a masking approach by comparing performance with an unmasked approach in terms of both detection and localization of a roadside nuclear threat. We simulate many instances of a drive-by scenario via Monte Carlo using empirical observations from the RadMap data to obtain background photons and synthetic injection of threat source. Simulation results suggest that the CA detector suffers significant loss of detection probability for weak sources, but only slightly for moderate source intensities. The masked approach also demonstrates consistent improvement in localization performance across all source intensities investigated. From these experiments we can begin to draw boundaries around the problem space in which CA detectors provide positive utility.

This paper describes a remote radiation imager used in environmental monitoring. The system consists of gamma ray detector, coded aperture mask, video camera, FPGA based digital electronics, ARM based control system and LED screen. The detector is based on custom designed 5*5 SiPM array and 11*11 YSO array, with the pitch of 1.8 mm. The modified uniformly redundant array coded aperture mask was used to ensure greater system sensitivity. The device can take image of the radiation field distribution, fuse it with optical image and then display the fused image in one picture on the screen. Preliminary experiment has been taken and the results showed the system to be full functional. The imager weighs 2.8 kg and is powered by lithium battery, which makes it the most portable among similar-type instruments.

Perspective high speed Adaptive Railroad Cargo Inspection System (ARCIS) is being developed at RadiaBeam Technologies. The idea of ARCIS relying on linac-based, adaptive, X-ray source of ramped energy packets of short X-ray pulses, new types of fast X-ray detectors, rapid processing of detector signals for intelligent control of the linac, and advanced radiography image processing. The requirements for such novel systems include high resolution (better than 5 mm line pair), penetration beyond 400 mm steel equivalent, high scan speeds (>10 km/h, up to 60 km/h), material discrimination (four groups of Z) with 100% image sampling for speed up to 45 km/h, low dose and small radiation exclusion zone. To meet and exceed these requirements, research into a new radiography methods and system design, and new detector materials has been initiated. To ensure ARCIS specification new S-band traveling wave linac with deep energy control has been designed. This linac will provide the packet of 400 ns X-ray pulses separated by the 100 ns gap with pulse energy ramping from 2 to 9 MeV within packet, and total beam power of up to 2 MW. This paper will discuss this and other requirements justification, the linac design approach and its principal components. A special attention will be given to electromagnetic design of the accelerating structure and the beam dynamics since they define the linac performance. Several important operational issues such as transient processes, thermal and mechanical performance will be covered. We will also discuss a novel multilayer X-Ray converter designed specifically for ARCIS to fully exploit advantages afforded by the ramped energy technique. Finally, some engineering, manufacturing and tuning aspects will be presented and discussed.

When evaluating detectors and algorithms for nuclear threat detection in populated environments, introducing actual sources is usually neither feasible nor economical. It is more practical to move the detector, (which is either airborne, vehicle-borne, or human portable) through the test environment and then to later artificially superimpose either measured or simulated source signatures on the recorded background data. We present a source injection algorithm that can be used to inject either measured or simulated source data into list-mode background data. It is designed to accommodate cases where measured "injection data" are available only at a limited set of locations. We describe a sampling scheme suitable for obtaining measured source injection data. We then use these data to demonstrate the source injection algorithm applied to list-mode data collected with a helicopter-borne detector system, where arbitrary detector poses and trajectories are possible. Stochastic methods are used both to select source events from a dataset containing both source and background events, and to scale the number of selected events to match the field conditions of detector-source distance, air attenuation, acquisition duration, and the relative strength of the measured and injected sources. This algorithm is planned to be used as part of the Airborne Radiation Enhanced-sensor System (ARES) Advanced Technology Demonstration.

The time-correlated pulse-height (TCPH) technique can be used to differentiate between multiplying and non-multiplying fission sources. In the past this technique proved effective at characterizing the multiplication of alpha phase plutonium metal through a passive measurement. Recently Sandia National Laboratories has completed a measurement campaign with its new Correlated Radiation Signature (CoRS) system involving active interrogation of highly enriched uranium (HEU) with an americium-lithium (Am-Li) source. Measurement results have shown Am-Li source to be a suitable interrogating source because of its relatively low-energy neutron spectrum. The TCPH technique was successfully used to determine the presence of a multiplying source when Am-Li source was sufficiently close to the material of interest. The presence of depleted uranium (DU) shielding limited the correlated pairs visible from the HEU. However, the effect of Lucite moderator on the inter-fission timing was noticeable in the TCPH distributions.

The High Efficiency Multimode Imager (HEMI) is a portable hybrid gamma ray imager based on CdZnTe coplanar grid detectors arranged in a fully populated backplane and partially populated (coded) front plane. This active mask arrangement provides coded aperture imaging for low energies and Compton imaging between planes for higher energies. The prototype instrument has been successfully fielded for aerial measurements in Fukushima Japan, however several imaging artifacts and field-of-view limitations were observed to arise from the parallel plane configuration. To overcome these limitations, a spherical arrangement of existing detector elements was proposed, and a prototype spherical HEMI instrument was designed with the same portable form factor and the same 96 detectors. Simulations indicate a lever arm distance (for the first two interactions) improvement of 4-10x over the parallel plane configuration. We present fabrication details and first results from this unique rotationally invariant hybrid imager. Additional 3D vision and spatial mapping tools will be integrated to form a unique Portable Radiation Imaging Spectroscopy and Mapping (PRISM) detection platform.