A double-helix neutron detector using micron-size 10 B powder

A double-helix electrode configuration is combined with a 10B powder coating technique to build large-area (9in.×36 in., or about 23cm by 91cm) neutron detectors. The neutron detection efficiency for each of the four prototypes is comparable to 3.7×103cm3 of 3He inside a cylindrical tube 91cm long. One unit has been operational continuously for 18 months and the change of efficiency is less than 1%. An analytic model for pulse height spectra is described and the predicted mean film thicknesses agree with the experiment to within 30%. Further detector optimization is possible through film texture, powder size, moderator box and gas. The estimated production cost per unit is less than 3k US$ and the technology is thus suitable for deployment in large numbers.