Neutron thickness gauge - for measuring hydrogenated layers esp surface water with neutrons slowed by paraffin or polyethy

摘要

One or more, pref. two, sources of rapid neutrons e.g. Am enriched Be, are set in a block of absorbent material, pref. paraffin or polyethylene, so that neutrons slowed to an energy of about 0.03 eV to 1 keV are released at a set distance from the surface of a layer of hydrogenated material of unknown thickness (in the region 0 to 5 mm). A detector count of reflected neutrons is used as a measure of the thickness of the hydrogenated layer. May be used for measuring the thickness of layers of emulsions or resins, but esp. for measuring the average depth of water lying on a wet road in studies of tyre friction, aquaplaning etc. with an accuracy of about 0.08 mm (of water).