2019 IEEE Nuclear Science Symposium and Medical Imaging Conference
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Scintillators, Photodetectors and Applications I

Session chair: Moszyński, Marek, (National Centre for Nuclear Research (NCBJ), Radiation Detector's Division, Świerk (Otwock), Poland); Zhu, Ren-yuan, (California Institute of Technology, 256-48, HEP, Pasadena, USA)
Shortcut: N-01
Date: Monday, 28 October, 2019, 1:40 PM
Room: Charter 1
Session type: NSS Session

This session is focused on systems, ranging from single detector instruments to apparatus based on a large number of units.


1:40 PM N-01-01

SiPMs for direct scintillation light detection in noble liquids (#2278)

T. Tsang1

1 Brookhaven National Lab., Upton, New York, United States of America


The extremely low dark count rate of the state-of-the-art vacuum ultraviolet sensitive SiPMs working in cryogenic temperature is about five orders of magnitude lower than at room temperature. However, the dark rate or the corresponding dark current of the same SiPM working in purified noble liquids of Ar, Kr, and Xe are generally higher. We show that the higher dark rate is caused by the nonzero scintillation light events triggered by environmental radio-activity in an ordinary laboratory at sea-level. Although these background scintillation light in noble liquids are in single-photon low light level, in some applications it might be a nonnegligible background.

Keywords: Photon dePhoton detectors for UV, noble gas and liquid detectors
1:58 PM N-01-02

Cryogenic SiPM technology for a direct dark matter detection experiment (DarkSide-20k) (#1477)

A. Mazzi1, F. Acerbi1, M. Marcante1, G. Paternoster1, V. Regazzoni1, N. Zorzi1, A. Gola1

1 Fondazione Bruno Kessler, Center for Materials and Microsystems, Trento, Italy


We describe the development of cryogenic silicon photomultiplier (SiPM) technology that was carried out at Fondazione Bruno Kessler (FBK) to meet the project requirements of DarkSide-20k (DS-20k) experiment. DS-20k is a direct dark matter detection experiment, which will be installed at INFN Gran Sasso National Laboratory, Italy. It is based on a time projection chamber filled with low background liquid argon (LAr). The photodetection modules of DS-20k are based on SiPMs, with a total photosensing area of 14 m2. SiPM technology allows flexibility in detector design and assembly, low power consumption, high efficiency and low background thanks to improved radiopurity. The dedicated development of FBK SiPMs, based on NUV-HD technology, led to a specialized version, known as NUV-HD-Cryo. The SiPM production process was deeply redesigned, with a lower peak electric field at the junction, a highly stable quenching resistor with small temperature variations, and a process adjustment to reduce correlated noise at cryogenic temperature. The resulting NUV-HD-Cryo SiPMs show a photon detection efficiency of 50% at 6 V excess bias, at 420 nm with 30 µm cells. The primary dark count rate is of 10 mHz/mm2 at 6 V, at LAr temperature, with 22% direct crosstalk probability and ~10% afterpulsing probability. These results are enabling for the use the use of SiPM in the readout of liquid scintillators, allowing large area photodetector readout with low background level. The assembly of test photodetection modules is now in progress and will allow in the next months to evaluate detector performance at cryogenic temperature with integrated electronic readout.

Keywords: cryogenic SiPM, dark noise, silicon photomultiplier (SiPM), dark matter, liquid argon
2:16 PM N-01-03

Characterization of CLLBC Coupled to Silicon Photomultipliers (#1524)

F. Liang1, J. Smith1

1 FLIR Systems, Inc., Oak Ridge, Tennessee, United States of America


Cs2LiLaBr6−xClx:Ce (CLLBC) has high energy resolution for gamma detection and high sensitivity for neutron detection. It is one of the neutron-gamma dual-mode scintillators developed in recent years. This work studies the performance of an 18 mm CLLBC cube for gamma and neutron detection for temperatures between –20 and 50 C. In addition, the scintillator was coupled to the SensL C- and J-series silicon photomultipliers (SiPMs) for comparison. Throughout the temperature range, better energy resolution is observed for the scintillator coupled to the J-series SiPMs which can be attributed to the higher photon detection efficiency. For neutron detection, the output of the detector was recorded by a waveform digitizer and analyzed offline on a computer. To distinguish neutrons from gammas, a pulse shape discrimination technique was utilized. A good separation between neutrons and gammas is observed for all the temperatures. However, separating neutrons from the intrinsic alphas is somewhat difficult at low temperatures. In spite of that, this 18 mm CLLBC is a high-performance scintillator and is suitable for deployment in radiation detectors for safeguard and security applications.

Keywords: CLLBC, silicon photomultiplier, neutron detection, gamma detection
2:34 PM N-01-04

Energy Resolution, Pulse Shape Discrimination, and Coincidence Time Resolution with CLLBC Scintillators Coupled to Silicon Photomultipliers (#2536)

J. W. Cates1, R. Pavlovsky1, K. Vetter1, 2

1 Lawrence Berkeley National Laboratory, Applied Nuclear Physics, Berkeley, California, United States of America
2 University of California Berkeley, Nuclear Engineering, Berkeley, California, United States of America


Cs2LiLa(Br,Cl)6:Ce (CLLBC) is a recently developed elpasolite scintillator with excellent energy resolution for gamma rays, and it is lithium-loaded for thermal neutron detection. The Cl content of the crystal also facilitates a channel for fast neutron detection, although with lower efficiency than the thermal absorption channel. Achievable energy resolution is typically <4% for 662 keV deposited energy, and differing ionization kinetics for hot recoil electrons from gamma interactions and heavy, charged particles resultant from thermal neutron absorption facilitate pulse shape discrimination between gamma and neutron interactions. In this work, we present achievable energy resolution, pulse shaped discrimination, and coincidence time resolution (CTR) with 1.2x1.2x1.2 cm3 and 2.4x2.4x5.0 cm3 CLLBC crystals from Radiation Monitoring Devices Inc. coupled to arrays of SensL-J SiPM arrays. With an optimized signal processing chain, energy resolution of ~3% is achievable at 662 keV energy deposition for 1.2x1.2x1.2 cm3 crystals and ~3.5% is maintained for the 2.4x2.4x5.0 cm3 crystals coupled to larger SiPM arrays at room temperature. A temperature probe inside the hermetically sealed packaging of the crystal and photosensor allows corrections to be applied to spectral data to maintain this energy performance across a large temperature range. Excellent pulse shape discrimination (PSD) between gamma and neutron events is observed for both crystal geometries (FOM>3) using standard tail-to-total methods and also techniques that facilitate PSD using only a single charge integrator and analog-to-digital converter (FOM>2.5). We also report on the CTR between identical pairs of 1.2x1.2x1.2 cm3 and 2.4x2.4x5 cm3 CLLBC crystals using a high frequency electronic readout designed to combat the large device capacitance of the SiPM array.

Keywords: CLLBC, SiPM, SiPM Array, Pulse Shape Discrimination, Neutron Detector
2:52 PM N-01-05

High-Speed, Efficient, High-Resolution Gamma Ray Imaging, The ClearMind Project (#1650)

D. Yvon1, V. Sharyy1, M. Follin1, J. - P. Bard1, D. Breton2, J. Maalmi2, C. Morel3

1 CEA, Paris-Saclay Univ, IRFU, Gif sur Yvette, France
2 CNRS-IN2P3, LAL-Orsay, Orsay, France
3 Aix-Marseille Univ, CNRS-IN2P3, CPPM, Marseille, France


The ClearMind project develops a monolithic gamma ray detector (0.5 MeV to few MeV) with a large area (≥25 cm2), high efficiency, high spatial accuracy (< 4 mm3 FWHM) and high timing accuracy.
We use PbWO4 scintillating crystals on which are directly deposited photoelectric layers of refractive index greater than that of the crystals.
The crystal is encapsulated with a micro-channel plate multiplier tube (MCP-PMT) with a densely pixelated anode plane, in order to optimize photo-electrons timing and positioning measurements. The MCP-PMT is read out using transmission lines and a SAMPIC fast waveform recorder.
Our detector assets consist in:

  • Improving the efficiency of light collection in a high-density, and high-effective atomic number crystal. We expect a factor 4 gain on light collection efficiency compared to conventional assemblies.
  • Using the Cherenkov light emission for detection. The gain in optical coupling optimizes the detection efficienvy of Cherenkov photons, inherently very fast.
  • Using the map of photoelectrons produced at the surface of the crystal to reconstruct the properties of the gamma interactions. The scintillation photons provide the necessary statistics for a measurement of the energy deposited in the crystal, modest but compatible with a use on a PET imager, and an accurate positioning of the gamma ray interaction.
  • Using the SAMPIC waveform recorder and transmission lines, which allows excellent timing and spatial resolution with a reduced number of readout channel.

We will present the detector concept and simulation results supporting the foreseen performances as well as measured performances of our prototype bialkali photocathode deposited on PbWO4. A companion paper (M. Follin et al.) will be devoted to the ultrafast MCP-PMT readout technologies using the SAMPIC waveform digitizers.
ClearMind  is patented: D. Yvon, and V. Sharyy, FR N° 17/59065, 29 Sept. 2017, « Détecteur de photons à haute énergie », Applicant : CEA

Keywords: Fast Gamma Ray detector, Cherenkov Detector, Scintillator Detector, Time Of Fligth PET detector
3:10 PM N-01-06

Development of x-ray talbot-lau imaging system using submicron-diameter phase-separated scintillator fibers (#2597)

K. Kamada1, 2, H. Yamaguchi1, K. J. Kim1, A. Yamaji1, V. Kochurikhin3, 2, S. Kurosawa1, Y. Yokota1, Y. Shoji2, 1, Y. Ohashi1, A. Yoshikawa1, 2

1 Tohoku University, Sendai, Japan
2 C&A Corporation, Sendai, Japan
3 Prokhorov General Physics Institute of RAS, Moscow, Russian Federation


The 25 x 25 mm2 wafers of Tb doped GAP/a-Al2O3 eutectic were fabricated by μ-PD method using the Ir crucible with a 25 x 25 mm2 die. The proto-type of X-ray phase imaging detector was developed using the  CMOS sensor with the FOP and eutectic wafer. X –ray spots with 8.24mm period was observed using the detector. X-ray phase imaging of the nylon ball was carried out in this study. It could be confirmed that a phase change of about 2 μm as the phase change occurs in the air and the nylon spherical interface. A technique of X-ray phase imaging could be realized in the absence of absorption grating.
In this study, X-ray phase imaging without absorption lattice using eutectic structure have demonstrated for the first time in the world.
It is possible to fundamentally solve the reduction in sensitivity and the accompanying increase in the amount of X-ray irradiation to the subject, which is a problem in conventional X-ray phase imaging using absorption gratings.

Keywords: Scintillator, eutectic, x-ray talbot-lau imaging

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