A Modified Fast Analog Technique for Determining Luminescence Decay Times of Scintillators

Abstract

We have modified our previous fast analog technique to determine the luminescence decay times of scintillators following an excitation with a Sr90β3-source. In the original technique [1], the sample was excited with a nitrogen-pumped dye laser, and the fluorescence pulses (consisting of typically 50 to 1000 photons) were detected by a multi-channel plate photomultiplier tube (MCP-PMT). The output from the MCP-PMT was directed to a fast waveform digitizer triggered externally by the exciting laser. In the modified technique, the digitizer acquires the fluorescence decay in the internal trigger mode, as no corresponding external trigger pulse is available from the Sr90source. For efficient light collection from scintillators, an ellipsoidal mirror assembly has been tested. The fluorescence decays are acquired as multi-photon pulses and are subsequently corrected for the temporal instrument response by using a deconvolution technique. The overall time resolution of the technique is about 100 ps. The fluorescence decay time obtained using this technique for a commercial scintillator (SCSN-81) agrees well with literature. We also discuss our results on new epoxy-polymer based scintillators prepared in our laboratory. The primary motivation for this work was development of new scintillators with shorter fluorescence decay times for high collision rate experiments.