Neutron detection and multiplicity counting using a boron-loaded plastic scintillator/bismuth germanate phoswich detector array

Technical Report · Sun Mar 01 04:00:00 EST 1998

DOI:https://doi.org/10.2172/663186· OSTI ID:663186

Miller, M C

Neutron detection and multiplicity counting has been investigated using a boron-loaded plastic scintillator/bismuth germanate phoswich detector array. Boron-loaded plastic combines neutron moderation (H) and detection ({sup 10}B) at the molecular level, thereby physically coupling increasing detection efficiency and decreasing die-away time with detector volume. Both of these characteristics address a fundamental limitation of thermal-neutron multiplicity counters, where {sup 3}He proportional counters are embedded in a polyethylene matrix. Separation of the phoswich response into its plastic scintillator and bismuth germanate components was accomplished on a pulse-by-pulse basis using custom integrator and timing circuits. In addition, a custom time-tag module was used to provide a time for each detector event. Analysis of the combined energy and time event stream was performed by calibrating each detector`s response and filtering based on the presence of a simultaneous energy deposition corresponding to the {sup 10}B(n,alpha) reaction products in the plastic scintillator (93 keV{sub ee}) and the accompanying neutron-capture gamma ray in the bismuth germanate (478 keV). Time-correlation analysis was subsequently performed on the filtered event stream to obtain shift-register-type singles and doubles count rates. Proof-of-principle measurements were conducted with a variety of gamma-ray and neutron sources including {sup 137}Cs, {sup 54}Mn, AmLi, and {sup 252}Cf. Results of this study indicate that a neutron-capture probability of {approximately}10% and a die-away time of {approximately}10 {micro}s are possible with a 4-detector array with a detector volume of 1600 cm{sup 3}. Simulations were performed that indicate neutron-capture probabilities on the order of 50% and die-away times of less than 4 {micro}s are realistically achievable. While further study will be required for practical application of such a detection system, the results obtained in this investigation are encouraging and may lead to a new class of high-efficiency, short die-away time neutron multiplicity counters capable of extending current nondestructive assay methods for special nuclear materials.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 663186
• Report Number(s): LA--13315-T; ON: DE98006019
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
BGO DETECTORS
COUNTING TECHNIQUES
DATA ACQUISITION SYSTEMS
DESIGN
EXPERIMENTAL DATA
NEUTRON DETECTION
NONDESTRUCTIVE ANALYSIS
PLASTIC SCINTILLATION DETECTORS
RADIOACTIVE MATERIALS
THEORETICAL DATA