The Adaptation of Multi-Wire Proportional Chambers with Delay-Line Readouts for Neutron Radiographic Imaging

A proportional chamber employing delay-line readout has been adapted for thermal-neutron imaging through the use of a boron converter plate as one of the chamber electrodes. A small prototype chamber using natural B for a converter has achieved 0.5% thermal-neutron-detection efficiency and better than 2 mm resolution (10% - 90% knifeedge). A converter-plate-model calculation gives good agreement with the measurements and shows how efficiency and resolution vary with chamber thickness, energy discrimination, and B and Alovercoating thicknesses. Substitution of 10B for the natural B would give a five-fold increase in efficiency and the calculations indicate that a further improvement in both efficiency and resolution of up to 50% is achievable in a single-plate system. The results of these calculations and a comparison with measurements are presented.