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Dual-Mode Fast Organic Isotopic Scintillators

Description:

TECHNOLOGY AREA(S): Materials, Sensors, Nuclear 

OBJECTIVE: The topic seeks to advance the current state of the art in materials research for the detection of SNMs and WMDs. The emphasis is on the efficient detection of neutrons as well as gamma-rays, with superior neutron/gamma discrimination and better gamma-ray energy resolution than that of NaI:Tl using fast organic materials that are deemed low cost and rugged. 

DESCRIPTION: Innovative approaches for low-cost organic scintillation materials that enable dual-mode, neutron/gamma radiation detection are sought. The proposed materials or systems may include new compositions and designs, or improve upon the existing ones through recently developed methods of materials and systems engineering. The key performance requirements are to develop dual-mode, e.g. sensitive to both neutrons and gammas, scintillators that can retain the excellent neutron detection and PSD characteristics of stilbene, while adding increased gamma-ray sensitivity and energy resolving capability for isotope identification, as well as providing faster decay time over stilbene for high count rate applications and TOF studies. The use of these materials will allow development of integrated detection systems capable of high count rates to utilize TOF techniques for neutron imaging and neutron energy information, dual gamma-ray and fast neutron detection with high sensitivity and PSD, better energy resolution and isotope identification than that of NaI:Tl. Commercial inorganic scintillators provide many of these characteristics but are often expensive and not available in large sizes, while organic single crystals such as stilbene provide efficient fast neutron detection and good PSD but lack gamma-ray spectroscopy and are still relatively expensive. Hence, in addition to the key performance requirements mentioned above, the proposed materials or systems must include a cost-benefit analysis relative to the commercially available options. It is anticipated that the proposed materials can be scaled to very large sizes in a cost effective manner unlike the current, state-of-the-art inorganic scintillator technologies. 

PHASE I: Phase I must demonstrate the feasibility of the selected materials and/or systems to provide efficient gamma-ray and neutron detection in combination with neutron/gamma PSD with a Figure-Of-Merit (FOM) equal to or better than that of stilbene, while having improved gamma-ray sensitivity and spectroscopic capabilities. Detectors or systems that can provide high count rates and TOF capabilities are preferred. At the end of Phase I, demonstrate pathways for scaling up the materials to 1” (diameter) x 1” (length), and meet the following performance goals: • Light yield greater than 10,000 photon/MeV; • Energy resolution better than that of NaI:Tl, or< 7% (FWHM) at 662 keV; • Faster scintillation decay time than that of stilbene (<2 ns); • Neutron/Gamma PSD equal to or better than that of stilbene (FOM> 3); • Unit cost of the materials/systems lower than that of stilbene. 

PHASE II: Further develop the chosen production methodology from Phase I and produce larger organic scintillators, e.g. > 3” (diameter) x 3” (length) with targeted performance goals. By the end of Phase II development, mature materials production process must be established, as well as pathways towards achieving low cost materials production. At the end of phase II, the goal is to fully commercialize 2” (diameter) x 2” (length) chosen organic scintillators, with the objective to commercialize even larger size crystals. Prototype instruments that integrate the chosen organic materials with optical readout, e.g. PMT or SiPM, shall be developed and demonstrated in Phase II and delivered to DTRA for further evaluation. 

PHASE III: Team up with national laboratories or commercial partners to develop commercial quality prototype instrument utilize the developed fast organic scintillator to accomplish the goals of neutron and gamma-ray detection in combination with efficient neutron/gamma PSD and gamma-ray spectroscopy. The commercial prototype instrument should provide unprecedented capabilities to DTRA for Warfighter’s missions, domestic security and commercial applications to support first responders and regulatory inspections, border and port security, power plant maintenance, and environmental clean-up, etc. 

REFERENCES: 

1: ​ANSI N42.34, American National Standard Performance Criteria for Hand-Held Instruments for the Detection and Identification of Radionuclides.

2:  ​G. Knoll, Radiation Detection and Measurement, Wiley, 2010.

3:  ​Market Survey Report

4:  https://www.dhs.gov/sites/default/files/publications/ND-PRD-MSR_0215-508_0.pdf.

KEYWORDS: Low-cost Fabrication Methods, Organic Scintillation Materials, Gamma-ray Detection, Neutron Detection, Neutron/gamma Pulse Shape Discrimination, Gamma-ray Spectroscopy 

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