Time Variant Filters for Generating Bipolar Pulses with Signal-to-Noise Ratios of Unipolar Pulses in Nuclear Pulse Amplifiers

Abstract

A time variant filter employing a simple gating technique was developed to produce bipolar pulses with signal-to-noise (S/N) ratios as good as those of unipolar pulses. The gated bipolar pulse discussed herein has an S/N ratio of a unipolar pulse shaped like the first lobe of the bipolar pulse. For the special case of symmetrical bipolar pulse shaping, the improvement in S/N ratio over the single measurement of the bipolar signal produced by conventional time invariant filters is 41.4%, and the improvement over the time invariant peak-to-peak measurement is 22.5%. The S/N ratio of the symmetric bipolar triangular pulse discussed in this paper is within 7.5% of the S/N ratio of the theoretically optimum unipolar pulse, but the system must be direct coupled from the radiation detector to the linear gate if count rate dependent peak shifts are to be avoided.