New Concepts in Nuclear Pulse Amplifier Design

Network analysis and synthesis techniques were applied to design a new experimental nuclear pulse amplifier whose performance is superior to any other similar type of amplifier. The amplifier is designed to closely approximate desirable overall transfer functions. The instrument consists of broadband, fixed-feedback amplifiers and a novel passive, linear lumped-element network. The gain of the amplifier is adjusted by passive, constant-impedance attenuators. The variation of crossover time with attenuator position (for both fine and coarse controls) is less than ±0.5 nsec, and it is not necessary to make separate trimming adjustments for each attenuator setting. The pulse-shaping network yields a unipolar output pulse having a monotonic return to the base line and having a theoretical signal-to-noise ratio superior to that of any published lumped-element network, and having minimum pileup distortion for a given noise-corner time-constant. The bipolar pulse has nearly equal-amplitude positive and negative peaks, but with no tertiary overshoot. No delay lines are used. Minimum pile-up distortion and excellent recovery from overload are achieved by the use of polezero cancellation techniques throughout the system. This amplifier was evaluated for overload recovery, crossover walk, pile-up distortion, common mode rejection, and noise-to-signal ratio.