A Dual Parameter Discriminator for Use with Gas Scintillation Proportional Counters

A new diagnostic tool has recently been developed at Los-Alamos for use in optimizing the performance of gas scintillation proportional counters. The instrument is a Dual Parameter Discriminator which allows for discrimination of nuclear pulses either by height, risetime, or both. This makes possible the generation of risetime spectra for different pulse height ranges, and pulse height spectra for different risetime ranges. The Dual Parameter Discriminator will easily measure risetimes up to about 45 microseconds. It has a lower risetime threshold of 100 nanoseconds, and will discriminate over the entire risetime range in 100 nanosecond increments, selected by front-panel thumbwheel switches. This wide dynamic range makes it useful in measuring the characteristics of large gas scintillation proportional counters which produce signals with risetimes too long to be measured using conventional techniques. The discriminator also has provision to store 0 to 5 volt pulse heights directly in an analog shift register, eliminating the need for capacitive holding circuits which are subject to droop and repeatability errors. The instrument contains both analog and digital outputs for connection either to a pulse height analyzer or computer.