N4B3  Neutron Detectors: Compact Neutron Detectors

Thursday, Nov. 5  10:30-12:10  Golden West

Session Chair:  Scott Kiff, Sandia National Laboratories, United States; John Mattingly, North Carolina State University, United States

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(10:30) N4B3-1, 'GP2' - an Energy Resolved Neutron Imaging Detector Using a Gd Coated CMOS Sensor

D. E. Pooley1, J. W. L. Lee2, M. Brouard3, R. Farrow4, J. J. John5, W. Kockelmann1, R. B. Nickerson5, N. J. Rhodes1, E. M. Schooneveld1, I. Sedgwick6, R. Turchetta6, C. Vallance2

1ISIS, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, UK
2Dep. of Chemistry, University of Oxford, 12 Mansfield Rd, Oxford, UK
3Dep. Physical and Theoretical Chemistry, University of Oxford, South Parks Road, UK
4Campus and Technology Hub, STFC Daresbury Laboratory, Keckwick Lane, Warrington, Cheshire, UK
5Dep. of Physics, University of Oxford, Denys Wilkinson Building, Keble Rd, UK
6Dep. Technology, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, UK

This paper reports on the new ‘GP2’ detector. It has been developed to meet the increased demand for energy resolved neutron imaging, a technique for which new beamlines are being built at spallation sources worldwide. The GP2 detector utilises a sensor developed for Particle Imaging Mass Spectrometry (PImMS), which records the time and the spatial position of a detection event, generating ‘event-mode’ data. It has been made neutron sensitive by directly sputtering gadolinium on the surface, which also makes it optically blind. It is read-out by a compact camera assembly measuring only 15cm x 15cm x 11cm, achievable because the detector does not require vacuum or cooling. The sensor can be operated in open air, extremely close to the sample. The active area of GP2 is 22.6mm x 22.6mm, with a pixel size of 70µm x 70µm. Each pixel has four independent 12-bit SRAM registers recording the detection time. I.e. each pixel can record four independent hits per frame with 4095 available time increments. By checking the occupancy of the four registers a user can immediately verify if the detector is being saturated at an early time, which would artificially modify the TOF spectrum. The smallest time binning available is ?t=12.5ns although a typical bin width at a neutron source is ?t=1µs. The option to construct complex time-gated measurement windows is integrated into the camera. Beyond experimental characterisation, the detector has been used to demonstrate its scientific capability. This has included elemental analysis, Bragg edge analysis, phase determination, shape/dimension measurement and tomographic reconstruction. A tomographic measurement of the engineering materials copper, brass and steel, embedded in aluminum will be presented. Details of the experimental validation of this specification and the scientific highlights will be presented as well as the development of a prototype multi-layered device and our proposal to increase the active area to 20cm x 20cm.

(10:50) N4B3-2, Neutron Imaging with LiInSe2: a Semiconducting 16-Channel Imager

E. H. Herrera1, D. S. Hamm1, E. D. Lukosi1, A. C. Stowe2, B. Wiggins2, A. Burger3, H. Bilheux4, L. Santodonato4

1Nuclear Engineering, The University of Tennessee Knoxville, Knoxville, TN, USA
2Y-12 National Security Complex, Oak Ridge, TN, USA
3Fisk University, Nashville, TN, USA
4HFIR CG-1D, Oak Ridge National Laboratory, Oak Ridge, TN, USA

Isotopically enriched in 6Li, the semiconductor lithium indium diselenide, LiInSe2 (LISe), has promising characteristics for neutron detection and imaging. As a solid-state detector, it offers both reduced power and size. These features also make LISe a prime candidate for unified imaging devices created by mounting the detector crystal directly to an integrated circuit. This effectively reduces the detector and front-end electronics down to a small circuit board, reducing the burdens of traditional neutron detectors. Our goal was to demonstrate a functional neutron imaging system using single crystal LISe as the detector volume. Imaging a steel hex bolt and the PSI Siemens star generated novel resolution data for the LISe sensor material. By proving the capability of a 16-channel system, the design is ready to adapt to a high-resolution digital system utilizing ASIC technology.

(11:10) N4B3-3, Advancements in Microstructured Semiconductor Neutron Detector (MSND)-Based Instruments

R. G. Fronk1, S. L. Bellinger2, L. C. Henson2, D. E. Huddleston3, T. R. Ochs1, C. J. Rietcheck1, J. K. Shultis1, T. J. Sobering3, D. S. McGregor1

1Mechanical & Nuclear Engineering Dept., Kansas State University - S.M.A.R.T. Laboratory, Manhattan, KS, USA
2Radiation Detection Technologies, Inc., Manhattan, KS, USA
3Kansas State University - Electronics Design Laboratory, Manhattan, KS, USA

Microstructured semiconductor neutron detectors (MSNDs) represent a low-cost, high-efficiency means of solid-state thermal neutron detection. Straight trenches are etched into a pn-junction diode and backfilled with nano-sized 6LiF neutron converting material. Neutrons absorbed within the conversion material produce charged reaction products that deposit energy within the semiconductor substrate can be detected. Presently, single-sided MSNDs are approaching their theoretical maximum detection efficiency with devices nearing 35% intrinsic thermal neutron detection efficiency, and represent an order-of-magnitude improvement over common thin-film-coated thermal neutron detectors. MSNDs are fabricated either as 1-cm2 or 4-cm2 active area diodes, depending on their intended application. The small size and high intrinsic thermal neutron detection efficiency of the MSND enables many of them to be arranged into larger and more sophisticated instruments. A small, inexpensive electronics package named the ‘Domino’ has been developed as a means to facilitate the deployment of the MSND technology. The Domino is a complete electronics package that fully supports a single MSND without NIM equipment by supplying the necessary bias, signal amplification, and TTL-pulse generation for neutron detection. The MSND-based Domino electronics package was tiled and arrayed to form large-area portable neutron detector arrays that were used to measure a small 252Cf source. A hand-held portable ‘Briefcase’ detector arrayed 84 Dominoes to form a 12 in. by 15 in. detector system, weighing 21 lbs. A vehicle-portable ‘Panel Array’ detector arrayed 480 Dominoes to 1 m by 1 m. The ‘Briefcase’ detector and the ‘Panel Array’ detector reported 0.27±0.01 cps ng-1 and 1.45±0.01 cps ng-1, respectively, for bare 252Cf at a distance of 2 m.

(11:30) N4B3-4, The Development of the Neutron Detectors for the China Spallation Neutron Source(CSNS)

Z. Sun

China Spallation Neutron Source, Detector Group, Institute of High Energy Physics, Chinese Academy of Sciences, Dongguan, Guangdong, China

The China Spallation Neutron Source (CSNS) in Guangdong, China will become the first spallation neutron source in China. CSNS is designed to accelerate proton beam pulses to 1.6GeV kinetic energy at 25 Hz repetition rate. The accelerator is designed to deliver a beam power of 200 kW with the upgrade capability to 500 kW by raising the linac output energy and increasing the beam intensity. CSNS construction was started in 2011 and would last 6.5 years. The CSNS’ first target station accommodates 20 neutron scattering instruments. These instruments present numerous challenges for detector technology in the absence of the availability of Helium-3, which is the default choice for detectors for instruments built today. Several kinds of neutron detectors were under study in the detector group, such as two-dimensional position sensitive neutron detector based on scintillator (NDBS), Multi-wire Proportional Chamber (MWPC), and Gas Electron Multiplier (GEM). The neutron detector based on scintillator (NDBS) consists of two layers of 6LiF/ZnS(Ag), two layers of crossed wave-length shifting fiber arrays, several multi-anode photo multiplier tubes (MA-PMT), and the ASIC readout electronics. The active area is 200 mm × 450 mm. The position resolution of 4 mm and a neutron detect efficiency with better than 50% are obtained. The high pressure MWPC with 6 atm. 3He and 2.5 atm. C3H8 has been constructed. The active area is 200 mm × 200 mm. The position resolution of 1.23 mm (FWHM) and an excellent linearity are obtained. A new thermal neutron beam monitor with a Gas Electron Multiplier (GEM) is also developed to meet the needs of the next generation of neutron facilities. A prototype chamber has been constructed with two100 mm×100 mm GEM foils.

(11:50) N4B3-5, New High-Resolution Gadolinium-GEM Neutron Detectors for the NMX Instrument at ESS

D. Pfeiffer1,2, F. Resnati1,2, J. Birch3, M. Etxegarai3, R. Hall-Wilton1,4, C. Hoglund1,3, I. Llamas-Jansa1,5, E. Oksanen1, E. Oliveri2, L. Robinson1, L. Ropelewski2, S. Schmidt1,3, C. Streli6, P. Thuiner2,6

1European Spallation Source AB, SE-221 00 Lund, Sweden
2CERN, CH-1211 Geneva 23, Switzerland
3IFM, Linkoping University, SSE-581 83 Linkoping, Sweden
4Mid-Sweden University, SE-851 70 Sundsvall, Sweden
5Institute for Energy Technology IFE, NO-2007, Kjeller, Norway
6Vienna University of Technology, 1040 Vienna, Austria

ESS instruments like the macromolecular crystallography instrument NMX require an excellent neutron detection efficiency, high-rate capabilities, time resolution, and an unprecedented spatial resolution in the order of a few hundred micrometers over a wide angular range of the incoming neutrons. For these instruments solid converters in combination with Micro Pattern Gas Detectors (MPGDs) are a promising option. A GEM detector with Gadolinium converter was tested on a thermal neutron beam at the IFE research reactor in Norway. The µTPC analysis, proven to improve the spatial resolution in the case of 10B converters, is extended to Gadolinium based detectors. For the first time, a Gadolinium-GEM was successfully operated to detect neutrons with an estimated efficiency larger than 10 % at a wavelength of 2 Å and a position resolution better than 500 µm.