Pulse Height Spectroscopical Measurements
3.2.6 Pile-up Rejection
Pile-up rejection is to prevent the spectroscopical filter to be applied to events too close
following each other to be evaluated properly. If there is another voltage step within the
length of the filter, the energies are partially or fully added. Pile up is a problem getting
increasingly worse with filter length and count rate. It can be easily seen as background
right of a peak and sometimes as pile-up peak at exactly double energy.
Recognizing pile-up is task of the trigger logic. The ability to prevent pile-up depends very
much on the time resolution, and therefore on the used trigger filter, see table 11.
The PUR setting is by default on, and may only be switched off for troubleshooting,
checking the performance of the pile-up rejector or with some really weird preamplifier
signals (overshoot or ringing).
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Figure 11: Lower end of a CZT spectrum. The counts left of the valley near 0keV are
caused by electronical noise and a too low trigger filter
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CZT373cs_02_7.spe
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