Current status of aerogel as a neutron converting material

Due to the recent ³He shortage, numerous alternative neutron conversion materials have emerged as potential ³He replacements. One such material is lithium-borosilicate aerogel which, unlike substrates coated with a neutron conversion material, is composed of the neutron conversion materials (Li and B) which are contained within the aerogel structural matrix. Additionally, silica-based aerogels can be utilized in high-temperature environments due to the material's high melting temperature range between 700-1000°C. Two different types of geometries of lithium-borosilicate were produced by Aerogel Technologies™ for a feasibility study in the use of aerogel as a neutron-conversion material. Neutron sensitivity testing of the samples was performed using a moderated-²⁵²Cf source and the resulting count rates, relative to background, indicate that the samples were sensitive to, and able to detect, neutrons. Additionally, simulations were performed using MCNP6 to define the optimal composition of a lithium-borosilicate aerogel sample containing macrochannels incorporated into the bulk of the sample. The resulting maximum theoretical thermal neutron detection efficiency was 45.2% for a sample containing 50% ⁶Li, 5% ¹¹B, 30% O, and 15% Si.