Time variant shaping

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Role of the pulse processor
Analog pulse shaping
Time variant shaping
Digital pulse shaping
Fixed process time
Adaptive pulse shaping
Resolution & count rate
Pulse pile-up protection
Comparing different pulse processors
Summary

The pulse processor

Time variant shaping can be used to overcome the calibration problems and rate sensitivity of analog shaping (Kandiah et al. 1975). By switching to a very short time constant right after the measurement is complete, the pulse returns very rapidly to the baseline. The shaping circuit can then be switched back to long time constants ready to measure the next voltage step. This method removes any count rate-induced shift but requires complex circuitry because each event has to be recognized as being present before the sequence of shaping can be initiated. In the absence of any real events, the electronics can also measure the voltage ramp, and therefore monitor the baseline automatically, so that changes in the slope of the ramp caused by variable detector leakage are compensated and peak shift is negligible.

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