Recent Developments in Neutron Detection and Multiplicity Counting with Liquid Scintillator

Recent Developments in Neutron Detection and Multiplicity Counting with Liquid Scintillator
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Total Pages: 11
Release: 2010
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ISBN:

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For many years at LLNL we have been developing time-correlated neutron detection techniques and algorithms for many applications including Arms Control, Threat Detection and Nuclear Material Assaying. Many of our techniques have been developed specifically for relatively low efficiency (a few %) inherent in the man-portable systems. Historically we used thermal neutron detectors (mainly 3He) taking advantage of the high thermal neutron interaction cross-sections but more recently we have been investigating fast neutron detection with liquid scintillators and inorganic crystals. We have discovered considerable detection advantages with fast neutron detection as the inherent nano-second production time-scales of fission and neutron induced fission are preserved instead of being lost in neutron thermalization required for thermal neutron detectors. We are now applying fast neutron technology (new fast and portable digital electronics as well as new faster and less hazardous scintillator formulations) to the safeguards regime and faster detector response times and neutron momentum sensitivity show promise in measuring, differentiating and assaying samples that have very high count rates as well as mixed fission sources (e.g. Cm and Pu). We report on measured results with our existing liquid scintillator array and progress on design of nuclear material assaying system that incorporates fast neutron detection.

Neutron and Gamma Pulse Shape Discrimination in a Liquid Scintillator Counter for Neutron Multiplicity Measurements of Enriched Uranium

Neutron and Gamma Pulse Shape Discrimination in a Liquid Scintillator Counter for Neutron Multiplicity Measurements of Enriched Uranium
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Total Pages: 8
Release: 2004
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ISBN:

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A new neutron multiplicity counter is being developed which utilizes the fast response of liquid scintillator (NE-213) detectors. Current uranium coincidence counting methods rely on the assay samples to conform to the calibration standards with respect to the sample uniformity, geometry, material type, etc. There exists a wide range of material throughout the DOE complex where these attributes are non-standard or unknown. A neutron counter with short die-away time makes possible the measurement of higher order coincidences. This information can be used to more accurately assay many of the problem items in the inventory. In addition, such a counter would allow for rapid inventory measurements of all forms of uranium. Liquid scintillator detectors also allow for energy discrimination between interrogation source neutrons and fission neutrons, allowing for even greater assay sensitivity. Liquid scintillator detectors are sensitive to? and neutron radiation. Differences in the timing of scintillation light produced in?-ray and neutron interactions allows for separation of these events using pulse shape discrimination (PSD). PMT pulses resulting from neutron and? interactions in the Liquid scintillator are read in using a fast waveform digitizer with a 1 GS/s sampling rate. The pulse shapes are then compared to? and neutron pulse templates and a?2 comparison determines the species. Integrated rise time can also be used to discriminate between they and neutron pulses. The results of these studies are presented.

Digital Data Acquisition Techniques ForFast Neutron Detection UsingLiquid Scintillator

Digital Data Acquisition Techniques ForFast Neutron Detection UsingLiquid Scintillator
Author: Ghulam Jaffar
Publisher:
Total Pages:
Release: 2007
Genre:
ISBN:

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The motivation of this project is to explore the use of digital pulse processing techniques for fast neutron and gamma ray detection in liquid scintillator. Digital techniques can simplify the performance of scintillation detectors where both timing information and pulse-height spectroscopy are required. Software based pulse shape discrimination (PSD) and timing algorithms have been developed that can be used in various neutron experiments in the time-of-flight (TOF) mode over a wide neutron energy range. These algorithms can be applied to current pulses produced directly from the photomultiplier tube and thus removing the need for processing electronics, which are typically required in an analog pulse shape system. The digital techniques developed in this study were applied to a large volume 'Demon' liquid scintillator detector. The Demon detector has a high intrinsic efficiency over a large energy range that is 50% for neutrons of 10 MeV and about 50% for y-rays of 1275 keV. During the normal Demon experiments the energy of fast neutron is measured using analog TOF methods.

Neutron Detection

Neutron Detection
Author: William Douglas Allen
Publisher:
Total Pages: 278
Release: 1960
Genre: Science
ISBN:

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