Year
2012
Abstract
The global critical shortage in 3 He gas has led to the introduction of neutron detector technologies based on other media. A significant class of these new technologies employs the 10 B medium as a coating in gaseous detectors, like Proportional Technologies’ small-diameter straws, GE’s boronlined tubes, Centronic’s boron-coated tubelets, and Precision Data Technology’s multi-plate detectors. We present performance simulations and supporting measurements of a straw-based multiplicity counter, replicating the dimensions of the 3 He-based High-Level Neutron Coincidence Counter (HLNCC-II). This counter has been designated as the initial target system for neutron replacement efforts supported by the DOE. The proposed counter replaces the 3 He tubes with straws, 4.43 mm in diameter, uniformly distributed within the counter’s polyethylene ring. Simulations include exploration of straw array pitch dimension ranging from 1.0 cm up to 1.6 cm and as well as variation of the 10 B4C coating thickness from 0.7 µm to 1.6 µm. Results show that high detection efficiency, in some cases exceeding that obtained in 3 He-based counters of equal dimensions, can be achieved, directly disproving the common notion that 10 Blined counters are limited to much lower efficiencies. Furthermore results show that die away time can match or exceed that of 3 He systems yielding improved figure of merit expressed as e 2 /t. Simulations also show that small-diameter straw detectors offer significantly better performance, compared to other 10 B-based solutions under evaluation for safeguards applications that employ suboptimal geometries such as 1\" tubes with thick coatings.