A novel method for detecting neutrons using low density high porosity aerogel and saturated foam

作者：Nelson Kyle A^*; Neihart James L; Riedel Todd A; Schmidt Aaron J; McGregor Douglas S

来源：NUCLEAR INSTRUMENTS %26 METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 2012, 686: 100-105.

DOI：10.1016/j.nima.2012.04.084

• He-3 replacement
• Neutron detection
• Aerogel
• Foam

As a result of the recent shortage of He-3 for neutron detection, several new detectors have been proposed as viable alternatives. Thin-film coated diodes and boron-lined proportional counters are suggested options, but both suffer from the %26quot;wall-effect%26quot;, where only one interaction product can be measured per event. The %26quot;wall-effect%26quot; greatly reduces the neutron detection efficiency of the device. A new method is presented using low-density high-porosity materials where both reaction products can escape the absorber and contribute to a single event. Measuring both reaction products simultaneously greatly increases the detection efficiency of the device. Experimentally obtained pulse-height spectra from saturated foam and borosilicate aerogel detectors are presented. Aerogel is a low-density solid, typically less than 50 mg/cm(3), and can be developed with B-10 in the structure. The thermal neutron response pulse-height spectrum from borosilicate aerogel is presented. Additionally, polyurethane foam, another low-density high-porosity material, was saturated with LiF and B2O3 to levels greater than 20 percent by weight and tested as a neutron detection medium. The foam saturated with 4.5 percent (LiF)-Li-6 was cut into 10 sheets, each 2 mm thick, and a neutron response pulse-height spectrum was collected. The thermal neutron detection efficiency was measured to be 7.3 percent, and the neutron to gamma-ray rejection ratio, acquired using a Cs-137 gamma-ray source, was calculated to be 1.71 x 10(6). Theoretical calculations also show that neutron detection efficiencies above 60 percent can be easily achieved using enriched (LiF)-Li-6 foam at 20 percent or higher saturation levels.

• 出版日期2012-9-11