N2B2  Photodetectors 1

Tuesday, Nov. 3  10:30-12:30  San Diego

Session Chair:  Lorenzo Fabris, Oak Ridge National Laboratory, United States; Jean-Francois Pratte, Universite de Sherbrooke, Canada

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(10:30) N2B2-1, Singe Photon Time Resolution of State of the Art Silicon Photomultipliers

M. V. Nemallapudi, S. Gundacker, P. Lecoq, E. Auffray

PH-CMX-DS, CERN, Geneva, Switzerland

Comparison of the timing performance of different Silicon Photomultipliers (SiPM) can be useful for applications that employ these devices. In this study, we characterize some of the currently available SiPMs to compare the single photon time resolution (SPTR) values measured using a 420nm picosecond laser. We present the SPTR results as a function of bias overvoltage and the leading edge discriminating threshold level. Photo-conversions beyond the active region, that give rise to tails in the delay histogram, are accounted by an exponentially modified Gaussian fit. SPTR values in the range of 60- 80ps (sigma) were measured for most 3x3 mm2 devices by Hamamatsu and FBK. Improvement in SPTR was observed for smaller SiPMs due to a decreased capacitance. Single SPADs from FBK yield SPTR values of the order of 30ps (sigma). We measured the uniformity of SPTR over different SPADs within a SiPM by focusing the laser to the level of a single SPAD. Further investigation on the source of variation in the timing performance of various devices is ongoing.

(10:50) N2B2-2, Search for an Optimal SiPM in Cherenkov TOF PET

R. Dolenec1,2, S. Korpar1,2, P. Križan2,3, R. Pestotnik2

1Faculty of Chemistry and Chemical Engineering, University of Maribor, Maribor, Slovenia
2Experimental Particle Physics Department, J. Stefan Institute, Ljubljana, Slovenia
3Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia

Sub 100 ps FWHM coincidence time resolution has been previously measured in a TOF PET experiment using the Cherenkov light produced in lead fluoride crystals. As photodetectors, MCP PMTs had been used due to their excellent time resolution. In later experiments the MCP PMTs had been replaced with SiPMs, which improved the efficiency of the method to levels comparable with established methods based on detection of scintillation light. However, the SiPMs have slightly limited time resolution and have a high dark count rate, which represents a serious issue for PET application at room temperature. In this contribution the results of experiments performed with SiPM produced by Hamamatsu, Ketek, Advansid and Sensl and at different overvoltages and temperatures will be presented.

(11:10) N2B2-3, Characterization of the First Prototypes of Ultra-High Density RGB Silicon Photomultipliers

A. Gola1, F. Acerbi1, A. Ferri1, A. Heering2, Y. Musienko2,3, G. Paternoster1, C. Piemonte1, R. C. Ruchti2, N. Zorzi1

1Fondazione Bruno Kessler, Trento, Italy
2University of Notre Dame, Notre Dame, USA
3INR RAS, Moscow, Russia

We characterized the first RGB SiPMs with Ultra-High-Density cells (RGB-UHD) manufactured at Fondazione Bruno Kessler (FBK), Trento. The devices have cell sizes of 7.5 um, 10 um and 12.5 um, arranged in a honeycomb configuration, corresponding to a cell density of 20500, 11500 and 7400 cells/mm2, respectively. For each cell size, we tested four layout splits, corresponding to different distances of the active area from the cell border. Depending on these splits, the fill factor (FF) of the cells varies between 33% and 57% and between 47% and 68%, for the 7.5 and 10 um cells, respectively. These cells have a very small capacitance and gain, thus featuring very fast recovery time, lower correlated noise and less sensitivity to radiation damage, when compared to larger cells built with a similar technology. Such characteristics are of great interest in applications that require high dynamic range and/or good resistance to radiation damage, such as the CMS ECAL upgrade. We tested samples of the UHD-SiPM technology, featuring a circular active area with 1.5 mm diameter. The experimental characterization showed that all the cell sizes and layout splits were working and were capable of single-photon resolution. The microcell recharge time constant was 3.5 ns and 4.5 ns, for the 7.5 um and 10 um cells, respectively. At an overvoltage of 6 V, we measured a correlated noise probability below 10 % for both the 7.5 and 10 um cells. DCR was in the order of 200 KHz/mm2. With the 10 μm cell having the highest FF, we measured a photon detection efficiency of 27% at 515 nm and 6 V over-voltage. In this contribution, we will report on the detailed electro-optical characterization of the RGB-UHD technology.

(11:30) N2B2-4, Development of Superconducting-Tunnel-Junction Single-Photon-Detectors Integrated with FD-SOI MOSFET Amplifiers

K. Kiuchi1, S.-H. Kim1, Y. Takeuchi1, K. Takemasa1, K. Nagata1, K. Kasahara1, K. Moriuchi1, R. Senzaki1, S. Yagi1, H. Ikeda2, S. Matsuura2, T. Wada2, H. Ishino3, A. Kibayashi3, H. Sato4, S. Mima4, T. Yoshida5, R. Hirose5, Y. Kato6, M. Hazumi7, Y. Arai7, I. Kurachi7, E. Ramberg8, M. Kozlovsky8, P. Rubinov8, D. Sergatskov8, S.-B. Kim8, S. Shiki9, M. Ukibe9, G. Fujii9, M. Okubo9

1University of TSUKUBA, Tsukuba, Ibaraki, Japan
2JAXA/ISAS, Sagamihara, Kanagawa, Japan
3Okayama University, Okayama, Okayama, Japan
4RIKEN, Wako, Saitama, Japan
5University of Fukui, Fukui, Fukui, Japan
6Kinki University, Higashiosaka, Osaka, Japan
7KEK, Tsukuba, Ibaraki, Japan
8Fermilab, Batavia, Illinois, USA
9AIST, Tsukuba, Ibaraki, Japan

We present a new high resolution single photon infrared spectrometer for cosmic neutrino background(C?B) radiative decay search. We plan to improve the lower limit on neutrino lifetime to 10^14 year with this device, while the current lower limit is 10^12 year. The detector is require to have energy resolutiond E /E = 2% for infrared photons(40-80 µm) for this experiment. The diffractive grating optics with the superconducting tunnel junctions(STJs) as an infrared single photon counting device is chosen. Each STJ consists of Nb/Al/AlxOx/Al/Nb layers and their thicknesses are optimized for the operation temperature at 300 mK cooled by the 3He sorption refrigerator. Our STJs achieved the leakage current 200 pA and the measured data implies that the smaller area STJ fulfills our requirement. Even with these excellent STJs, the electron-like signal charges produced in the STJ is only 100 electrons for the 40 µm photon. FD-SOI MOSFETs are employed to amplify the STJ signal in order to increase signal-to-noise ratio(S/N). FD-SOI MOSFETs can be operated at cryogenic temperature of 300 mK, which reduces the noise of the signal amplification system. We report on three topics: (i) FD-SOI MOSFET based read-out circuit design (ii) FD-SOI MOSFET detailed characteristic at cryogenic temperature (iii) Thermal effects in STJ due to heat generation by FD-SOI MOSFET.

(11:50) N2B2-5, The VSiPMT: Progress on the Realization of a Larger Prototype

F. C. T. Barbato1, G. Barbarino1, L. Campajola1, R. De Asmundis2, G. De Rosa1, F. Di Capua1, P. Migliozzi2, C. M. Mollo2, D. Vivolo2

1University of Naples, Naples, Italy
2INFN - National Institute for Nuclear Physics, Naples, Italy

The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design for a revolutionary hybrid photodetector. The idea, born with the purpose to use a SiPM for large detection volumes, consists in replacing the classical dynode chain with a SiPM. In this configuration, we match the large sensitive area of a photocathode with the performances of the SiPM technology, which therefore acts like an electron detector and so like a current amplifier. The excellent photon counting capability, fast response, low power consumption and great stability are among the most attractive features of the VSiPMT. In order to realize such a device we first studied the feasibility of this detector both from theoretical and experimental point of view, by implementing a Geant4-based simulation and studying the response of a special non-windowed MPPC by Hamamatsu with an electron beam. Thanks to this result Hamamatsu realized two VSiPMT industrial prototypes with a photocathode of 3mm diameter. We now present the results of a full characterization of the VSiPMT industrial prototypes with their pro and contra and the preliminary tests we are performing to improve the VSiPMT features in the realization of a 2-inches and 3-inches VSiPMT prototype .

(12:10) N2B2-6, Photomultipliers with the Screening Grid at the Anode for TOF PET Block Detectors

M. Moszynski1, T. Szczesniak1, M. Grodzicka1, R. Leclercq2, A. West2, M. Kapusta3

1National Centre for Nuclear Research,, Otwock-Swierk, Poland
2ADIT, Sweetwater, Texas 79556, USA
3Molecular Imaging, Siemens Healthcare, Knoxville, TN 37932, USA

In spite of the excellent performance of SiPMs in application to the time-of-flight PET detectors, a development of a better photomultipliers for PET detectors is of importance. Timing depends mainly on detector time jitter and its quantum efficiency, thus improvements of these parameters is an obvious advantage. However, several studies in the past showed that a screening grid at the anode against a parasitic component induced at the anode by electrons traveling towards the anode from the preultimate dynode, improves significantly time resolution measured with scintillation detectors. ADIT Co. has started a development of a 1” diameter fast PMT with the screening grid at the anode to be applied in the block detectors in TOF PET scanners. In the present studies, we report on the first comparative study of the L25, classical PMT, with that equipped further with the screening grid. Improvement of time resolution up to 1.2 factor over PMT without screening grid and shift of the optimal time pick-off point to the first photoelectrons are main reasons for improvement in timing performance of PMTs with screening grid at the anode.