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Neutron Imaging

Session chair: Clarke , Shaun D. (University of Michigan, Department of Nuclear Engineering & Radiological Sciences, Ann Arbor, USA); Monterial , Mateusz
Shortcut: N-07
Date: Tuesday, 19 October, 2021, 11:45 AM - 1:45 PM
Room: NSS - 3
Session type: NSS Session


Click on an contribution to preview the abstract content.

11:45 AM N-07-01

Neutron Imaging Using Organic Glass Scintillators (#880)

S. D. Clarke1, R. Lopez1, N. Giha1, W. Steinberger1, S. A. Pozzi1

1 University of Michigan, Department of Nuclear Engineering and Radiological Sciences, Ann Arbor, Michigan, United States of America


In this work, we develop of a compact neutron imaging system based on organic glass scintillator and silicon photomultiplier arrays. The recently developed organic glass scintillator has excellent neutron and gamma-ray detection efficiency and exhibits pulse shape discrimination capability that is nearly as good as current state-of-the-art materials such as trans-stilbene. We have cast and characterized 6 mm by 6 mm by 50 mm pillars of organic glass in our laboratory. When coupled to a silicon photomultiplier array, these pillars demonstrated better energy and timing resolution than the stilbene organic scintillator. This performance makes organic glass an ideal material for a compact neutron imaging system, which must resolve neutron scatter events on a sub-nanosecond time scale. We have demonstrated neutron imaging with pillars of organic glass scintillator coupled to arrays of silicon photomultipliers. Additional pillars of organic glass will be implemented into the system to improve the efficiency and imaging performance. The resulting system will be demonstrated using 252Cf and PuBe neutron sources in our laboratory. In addition, we will compare imaging performance to other compact neutron imaging systems that exist in literature.

Keywords: Organic glass scintillator, neutron imaging, pulse shape discrimination
12:00 PM N-07-02

Design and Commissioning of a Monolithic Neutron Scatter Camera (#1161)

J. Balajthy1

1 Sandia National Lab, Radiation and Nuclear Detection Systems, Livermore, California, United States of America

SVSC Collaboration


The Single Volume Scatter Camera (SVSC) Collaboration is a multi-institution effort led by Sandia National Laboratories to develop portable neutron imaging systems for a variety of applications in non-proliferation and arms control. Conventional neutron imagers are composed of several separate detector volumes organized in at least two planes. A neutron must scatter in two of these detector volumes for its initial trajectory to be reconstructed. As such, these systems typically have a large footprint and poor geometric efficiency. We report on the design and commissioning of a prototype monolithic neutron scatter camera that is intended to significantly improve upon the geometrical shortcomings of conventional neutron cameras. This device is the second monolithic prototype produced by the SVSC collaboration and utilizes a similar form factor to that of its predecessor. The detector volume is a block of EJ-204 plastic scintillator with dimensions (50mm x 56mm x 60mm). Two opposite faces of the scintillator block are optically coupled to arrays of 64 Hamamatsu S13360-6075PE silicon photomultipliers (SiPMs), which replace the H12700 multi-anode PMTs used in the previous prototype. The use of arrays of individual SiPMs allows electronic crosstalk to be well controlled but increases the dark rate of the device and introduces correlated noise sources from after-pulsing and optical crosstalk. Characterization studies on these systematic effects are presented here.

Keywords: Neutrons, Photodetectors, Position sensitive particle detectors, Silicon devices
12:15 PM N-07-03

Compact, High-Speed Pixel Design in Neutron Imager for Reflectometry (#585)

E. B. Johnson1, M. Kaffine1, C. Sosa1, E. van Loef1

1 Radiation Monitoring Devices, Watertown, Massachusetts, United States of America


To fully utilize the upgrades to the Spallation Neutron Source at Oak Ridge National Laboratory for neutron reflectometry, a high-speed, neutron-imaging device is required.  The neutron imager design requires a detection efficiency of 60% for 2 Å neutrons for event rates exceeding 2 Mcps per cm2 with less than 10% dead time.  The instrument design discussed in this work is based on detecting neutrons with an organic glass scintillator loaded with a boron compound and integrated with silicon photomultipliers connected to high-speed digital electronics.  With a high concentration of 10B, the scintillator thickness could be less than 1 mm to achieve 60% detection efficiency for 2 Å neutrons, and a thinner scintillator improves gamma ray rejection.  A technique using time over threshold in combination with pulse height discrimination can provide gamma-neutron separation within a time frame of 500 ns.  The readout concept is scalable for a high number of imaging pixel elements (scintillator and 1 mm SiPM) to obtain a 15 cm x 15 cm imaging unit.

AcknowledgmentThe effort was supported in part by the Department of Energy SBIR Grant (DE-SC0020610).  We are thankful for the support from Dr. Jason Hayward (UTK) and Dr. Richard Riedel (ORNL).
Keywords: Neutron Reflectometry, Digital Signal Processing, Pulse Shape Discrimination
12:30 PM N-07-04

Position reconstruction of double neutron scatters in a single-volume scatter camera (#1069)

J. Nattress1, M. Folsom1, M. Blackston1, L. Fabris1, K. Ziock1, B. Cabrerra-Palmer2, J. Brown2, E. Brubaker2, P. Hausladen2

1 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
2 Sandia National Laboratories, Livermore, California, United States of America


This presentation reports first experimental reconstruction of neutron double scatter events in a monolithic single volume neutron scatter camera (SVSC). For the monolithic SVSC concept to work, it is necessary to reconstruct the time and position of multiple neutron interactions in a single volume of organic scintillator (e.g., EJ-204) from the time and spatially dependent scintillator light pattern detected at the surfaces of the scintillator. This task is made difficult by the typical proximity in time and space of multiple interactions of the same neutron in a compact detector. To demonstrate accurate event reconstruction, a set of events is needed of which a significant fraction consists of two hydrogen scatters. To address this need, data enriched with neutron double scatter events were recorded using a setup consisting of a source, the SVSC, and a scatter detector positioned to require a 90-degree scatter in the SVSC. By selecting the time of flight between the SVSC and scatter detector, a subset of events is identified where more than 50% of events consist of double hydrogen scatters. Results from reconstruction of these events will be reported.

Keywords: single volume, neutron scatter
12:45 PM N-07-05

Development of a neutron imaging sensor based on event-driven silicon-on-insulator pixelated device (#1314)

L. Zhang1, M. Uenomachi2, K. Shimazoe1, H. Takahashi1, A. Takeda3, Y. Kamiya4, K. Mori3, T. G. Tsuru5, I. Kurachi7, Y. Arai6

1 University of Tokyo, Graduate School of Engineering, Tokyo, Japan
2 RIKEN, Nishina Center for Accelerator-Based Science,, Saitama, Japan
3 University of Miyazaki, Department of Applied Physics and Electronic Engineering,, Miyazaki, Japan
4 University of Tokyo, Department of Physics and International Center for Elementary Particle Physics, Tokyo, Japan
5 University of Kyoto, Kyoto, Japan
6 KEK, High Energy Accelerator Research Org., Tsukuba, Japan
7 D&S Inc., Tokyo, Japan


We have developed a neutron imaging pixelated sensor based on 10B coated XRPIX7 event driven SOI-CMOS pixel silicon device. XRPIX7 is aimed to operate the event driven mode, which can readout the energy deposition pattern with the programmed area size through the in-pixel trigger function. XRPIX can achieve high coincidence time resolution (~1 μs), superior readout time (~10 μs) and wide bandpass (0.5-40 keV). In this study, neutron irradiation test is performed to investigate sensor’s response. With time-of-flight measurement by the event driven XRPIX7 neutron imaging sensor, neutron events are successfully identified. By the energy deposition pattern, the capability to classify the neutron events and other events is confirmed. This will be useful for the applications that require neutron/γ recognition.

Keywords: imaging sensor, semiconductor, neutron
1:00 PM N-07-06

A Multimodal Gamma-ray and Neutron Imaging and Mapping System and Upgrades to Real-Time Signal Processing (#1451)

R. Pavlovsky1, J. Cates1, K. Vetter1, 2, M. Turqueti1

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


Abstract—Lawrence Berkeley National Lab (LBNL) has previously
demonstrated gamma-ray mapping of point and distributed sources using
small unmanned aerial systems (sUAS) and in handheld configurations
with monolithic CLLBC detectors in the Neutron and Gamma-Ray
Source Localization and Mapping Platform (NG-LAMPv1). NG-LAMPv1
has been extensively demonstrated to provide gamma-ray and neutron
mapping in 3D and real-time with Scene Data Fusion (SDF). SDF,
implemented on our Localization and Mapping Platforms (LAMP),
enables 3D scene capture via LiDAR data fused with radiation data that
is co-collected. We report on a next-generation LAMP system, enabling
gamma-ray imaging via Compton and coded mask modalities as well
as neutron imaging via coded mask implementations. The new system,
dubbed NG-LAMPv2, consists of nominally 64 detector elements of 1.27 x
1.27 x 1.27 cm3 CLLBC scintillators, which provide enhanced resolution
for coupled gamma-ray and neutron mapping in 3D and with ∼4% global
energy resolution at 661.7 keV. In this work, we show select results from
the completed system in sUAS configurations, as well as report on data
acquisition upgrades to perform real-time digital signal processing for
enhanced performance in portable configurations. A preliminary result
with our new data acquisition chain shows 3.2% energy resolution at
661.7 keV for a single module.

AcknowledgmentThis material is based upon work supported by the Defense Threat Reduction
Agency under IAA DTRA 10027-30527 and DTRA 13081-36242. This support does
not constitute an express or implied endorsement on the part of the United States
Government. Distribution A - distribution is unlimited.
Keywords: Gamma-ray Imaging, Gamma-ray Mapping, Neutron Mapping, Neutron Imaging, real-time signal processing
1:15 PM N-07-07

PSD_CHIP: A Highly Programmable SiPM Readout ASIC for Neutron Imaging Applications (#154)

J. Johnson1, B. Boxer1, S. Hillbrand1, V. Cottles2, C. R. Grace3, G. Wagner2, M. Tripathi1

1 UC Davis, Department of Physics and Astronomy, Davis, California, United States of America
2 ARC, White Bear Lake, Minnesota, United States of America
3 LBNL, Engineering, Berkeley, California, United States of America


Silicon Photomultipliers (SiPMs) are becoming widely used as replacements for photomultiplier tubes (PMTs) in photo-detection. In conjunction, suitable scintillators are being developed and improved for fast neutron/gamma discrimination applications. As such, there is a rising demand for suitable electronics to serve both as front-ends for high density SiPM array readout and to aid in particle discrimination. The latter is a crucial capability needed for neutron imaging systems. PSD_CHIP is an ASIC designed to demonstrate these two key components for a portable neutron imager system’s electronics. It provides a scalable multi-channel SiPM readout front-end system and a novel fast analog pulse shape discrimination (PSD) method. The chip’s front-end system is explicitly designed for readout of SensL SiPMs, which have two coupled outputs: a capacitively coupled fast output (FOUT) and a resistively coupled standard output (SOUT). The ASIC features a high level of programmability on- chip to allow for adapting for use with various scintillators in a final integrated neutron imaging setup. PSD_CHIP has been designed and submitted for fabrication.

Keywords: fast neutrons, gammas, imaging, PSD, SiPMs
1:30 PM N-07-08

Optically Segmented Single Volume Scatter Camera for Neutron Imaging: Interaction Position Calibration (#640)

P. E. Maggi1, K. Keefe2

1 Sandia National Laboratory, Livemore, California, United States of America
2 University of Hawaii at Manoa, Department of Physics and Astronomy, Honolulu, Hawaii, United States of America

On behalf of the SVSC Collaboration


We present an updated silicon photomultiplier (SiPM) based, optically segmented neutron imager that advances previous designs presented by the Single Volume Scatter Camera collaboration. Previous work by the University of Hawaii demonstrated a 64 channel system, though it suffered from a difficult calibration procedure and high electrical crosstalk. The current 16 channel imager was created with a modular design for ease of calibration and scalability. The imager module in this work consists of 16 Teflon wrapped EJ-204 bars (20 cm long, 5 mm x 5 mm square cross section) coupled to SensL J-series SiPMs at each end (6.13 mm x 6.13 mm, 6.33 mm pitch). The bars are arranged in two columns of 8 bars, and each end (18 channels, 16 SiPMs + 2 trigger lines) was read-out by a custom DRS4-based data acquisition board. Position calibrations were performed using a Na-22 source to provide coincident 0.511 MeV gamma rays. A tag-detector, a 50mm x 6 mm x 6mm transStilbene bar wrapped in Teflon, coupled to a single J-series SiPM, mounted to a linear stage was scanned along the length of the assembly. The signal from the tag SiPM was input into a DG535 pulse generator which provides a logic pulse to simultaneously trigger each data acquisition board. The interaction position within the detector was reconstructed using two methods: the time difference between the pulse rise at each end of a bar and the logamplitude ratio (LAR) of the pulse height at each end of a bar. The aggregate position resolution across all bars with the time-based method was 40.1 + 9.9 mm, and 46.3 + 6.5 mm with the log-amplitude method. The best linear unbiased estimate (BLUE) gives position resolutions of 29.5 + 4.2 mm. These values are preliminary and indicate a degradation compared to the previous single EJ-204 bar paper which measured a BLUE of approximately 10 mm.

AcknowledgmentSNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
Keywords: Neutron Imaging, Radiation detection

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