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Portable, Fieldable, Non- Helium-3 Based Neutron Multiplicity Counter



TECHNOLOGY AREA(S): Electronics, Nuclear Technology, Sensors

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 5.4.c.(8) of the solicitation.

OBJECTIVE: To develop a portable, fieldable neutron multiplicity counter based on non-Helium-3 neutron detection technology. A Helium-3 replacement medium would have similar or better performance in the key areas of neutron detection efficiency and gamma-rejection while minimizing dead-time and double-pulsing. A new medium should also permit comparable or better size, weight, and power consumption to existing Helium-3-based systems.

DESCRIPTION: DTRA seeks to develop a neutron multiplicity counter based on non- Helium-3 neutron detection technology. A neutron multiplicity counter does not simply record that a neutron was counted, but also when. To be an effective medium when applied to neutron multiplicity counting, detection efficiency is of paramount importance. The threshold neutron absolute detection efficiency is 0.5% for either bare Cf-252 source or Cf-252 source with 1” polyethylene shield at 50 cm distance. At the same time, gamma-rays must be rejected and the twin toxic effects of double- pulsing (where a single neutron gets counted as two) and dead-time (any period after a neutron is counted when the detector is blind) must be thoroughly abated. The detector shall be insensitive to gamma-rays in 1 R/hr Ba-133 gamma field and shall be able to operate in presence of low dose radiography X-ray equipment (e.g. XRS-3@ 8 ft). A timing resolution on the order of tens of nanoseconds or less would also be highly desirable. The electronics shall be able to support data rate up to 500,000 neutron counts per second. Any Helium-3 replacement needs to permit construction of a rugged instrument for field-use that is physically robust, insensitive to adverse environmental conditions[1], and has reasonable size, weight, and power consumption. The detector shall be able to operate on battery power for a continuous 10 hours period at 20 ºC and capable of running from AC power. The charging time for rechargeable battery shall be less than 6 hours and the battery compartment shall be accessible without special tools. The detector shall be able to fit through an 18 inch opening, weighs less than 50 lb, and support removable Cadmium or Gadolinium shielding for optimal configuration.

PHASE I: Identify key operational components and develop the initial design of the multiplicity counting instrument. Extensive modelling studies must be performed to demonstrate detector sensitivity, meet the physical, power consumption, timing resolution and data rate requirements. Demonstrate pathways to meeting performance goals in Phase II.

PHASE II: Develop a prototype instrument that accomplishes the goals described above. The instrument shall not be dependent on post-acquisition analysis of data. Typical multiplicity counting requires list-mode data acquisition. Demonstrate the neutron multiplicity counting capability equivalent to the most advanced portable multiplicity counter based on Helium-3.

PHASE III DUAL USE APPLICATIONS: Team up with national laboratories or commercial partners to develop a commercial instrument, for military applications of interest to DTRA as well as domestic applications (FBI, Department of Energy, etc) to support missions responding to an improvised nuclear device (IND) deployed by adversaries using irregular means.


  • MIL-STD-810G, Environmental Engineering Considerations and Laboratory Tests.

KEYWORDS: Portable, field useable, neutron multiplicity counter


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