Active D-C Restoration in Nuclear Pulse Spectrometry

It is well-known that while the use of single clipping yields optimum energy resolution in nuclear pulse spectrometry it suffers from the drawback of producing rate-dependent baseline shifts. On the other hand the use of double clipping removes the baseline shift but degrades the signal-to-noise ratio. A scheme has been devised which circumvents some of these problems by producing a signal proportional only to the peak-to-peak excursion of an input signal. When operating with double clipped signals this improves the signal-to-noise ratio and also reduces tail-pile-up difficulties. Single clipped signals can also be used and produce an output amplitude which is independent of baseline position, allowing the use of single clipping at high counting rates, although in this case the system exhibits a noise disadvantage. The technique employed is based on the principle of "active D-C restoration" and circuit details, together with representative results, are given.