A TECHNIQUE TO OPTIMIZE THE TIME RESOLUTION OF NE213 SCINTILLATION DETECTORS

A technique has been described to optimize time resolution of NE213 scintillation detectors. The technique involves minimization of transit time spread and space charge effects in the photomultiplier. The photomultiplier space charge effect was minimized by optimizing the voltage between the photocathode and the first dynode while the transit time spread was minimized by using a 6th dynode signal as timing signal instead of a conventional anode signal. During these studies the time resolution of the detector for correlated gamma rays from Na-22 and Co-60 as well as their ratio was used as a check for optimization of detector time resolution. The detector time resolution is improved by 14 and 21% for Na-22 and Co-60 sources when voltage between the photocathode and the first dynode is optimized. By using the 6th dynode signal for timing analysis, a further improvement of 4 and 6% is achieved in the detector time resolution for Na-22 and Co-60 sources respectively.