Design of neutron detectors utilizing luminescent glass

The impetus for the development of new neutron detector designs has come from the worldwide commissioning of neutron spallation sources. The feature of these sources is their broadband neutron emission and the consequent potential which they provide for neutron investigation of all types of structures in materials ranging from biological molecules to steels. The primary advantage of conventional neutron detectors filled with boron fluoride or helium 3 gas is their intrinsically low background count; their major drawback is a slow response time, high cost, and relative inflexibility in design for coping with large areas or complex geometry detection. This paper presents design strategies for glass neutron scintillators. These lithium silicate glasses, doped with Cesium ions, have high detection efficiencies for neutrons, fast decay times, total flexibility in shape and emission centered at 400 nm, and can be well matched to PM and image intensifier photocathodes. The neutron counting applications require one or a combination of the following systems: for neutron flux counting, a slice of glass of appropriate thickness coupled to a PM/photodiode feeding an operational amplifier and scaler; with no appreciable x-ray or other interfering radiation present, a slice of glass oc appropriate thickness coupled to a PM, a Schmitt trigger, and a window discriminator; for low signal-to-noise ratio, a sandwich layer construction