GB724223A - Improvements in and relating to phosphorescent materials - Google Patents

Abstract

A phosphorescent material for use in the detection and measurement of thermal neutrons comprises a sintered mixture of an alkali borate and silver-activated zinc sulphide in approximately equal parts by weight. The alkali borate can be sodium tetraborate or lithium tetraborate. The material can be prepared by mixing the alkali borate with silver-activated zinc sulphide in approximately equal parts by weight and sintering the mixture by heating at a temperature in excess of the melting point of the borate but not greater than the melting point of the zinc sulphide. The mixture can be sintered in air, an inert atmosphere or vacuo for approximately 10 to 20 minutes at a temperature between 800 DEG C. and 1000 DEG C. After cooling, the material appears in large chunks which can be reduced in size to large granules having a greatest dimension of the order of one-eighth of an inch. Greater efficiencies per unit volume of the phosphor can be obtained by using sodium tetraborate enriched in the isotope B10 or lithium tetraborate enriched in the isotope B10 and/or Li6. A thermal neutron flux can be detected by pulverizing the phosphorescent material and mixing it with oxygenated tetraethylene glycol dimethacrylate prepared in accordance with Specification 724,188. The mixture is coated on a sheet of polymeric methyl methacrylate and air excluded therefrom to produce hardening. The resulting article will produce light when exposed to a thermal neutron flux and can be utilized with any light sensitive devices or media for detecting neutrons, for example a photographic plate positioned adjacent the article. Specification 473,715, [Group III], also is referred to.