Achieving high rates with CsI(Tl)-photomultiplier detectors

It is noted that a CsI(Tl) crystal together with a photomultiplier makes a very efficient detector for particle identification. However, its drawback, for high signal dynamics, is the low counting rate (typically several hundreds counts/s). The authors propose two remedies which enable this detector to have counting rates greater than 10000 counts/s. The first is a reliable pile-up detection scheme, based on a novel type of signal arrival recognition. This scheme can work for signal dynamics up to 100. The implementation implies signal shortening (200 ns) and low-level discriminator/pulse duration decoding logic. The second is a scheme that prevents the photomultiplier from being operated at high instantaneous and average currents. This is accomplished by shorting three stages of the photomultiplier, which gives a smaller gain. Good dynode HV (high voltage) stabilization was also implemented.<
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