Light collection systems for thin film scintillation detectors

Three different designs for light guides used with thin film scintillators employed as δE detectors are described. Each system was tested in nearly identical conditions and configurations except for the light-scattering mechanism, using NE102A and Pilot B films and alpha-particles. Light-collection efficiencies, as well as energy and time resolutions are compared. It was found that simple hollow cylindrical reflector in which the reflective surface was produced by vacuum evaporation of aluminium on a thin plastic sheet, was an efficient light guide for large-area thin-film scintillation detectors. Coupled to two matched and selected RCA 8850 phototubes operated in coincidence mode, this system was capable of giving a pulse height resolution of 21% and time resolution of 0.4 ns for a 1.1 mg/cm2 NE102A detector and alpha-particles of 5.48 MeV incident energy. The TFD mounting feature of this design allows a comparison of different detectors without disturbing any other parameter. It thus provides a very effective system for testing and comparing the properties of thin scintillator films on a very reliable basis. (orig.)