252Cf-plasma desorption mass spectrometry multistop time digitizer

Abstract

A multistop time digitizer is described which was designed specifically for 252Cf-plasma desorption time-of-flight mass spectrometry. The digitizer is a high resolution time intervalometer capable of measuring the times of a number of stop events following a common start. A resolution of 78.125 ps is achieved. The time range can be varied from 5 ms to 320 ms in 16 steps. Stop event processing time takes less than one microsecond, enabling high resolution measurements of closely spaced bursts of events. The digitizer consists of the following three modules. A clock module provides the accurate time reference including a precision time calibrator. An analog module contains a special tandem stretcher by which the high resolution and low differential nonlinearity are achieved. A digital module comprises the counting, logic and interface circuits. Up to four complete digitizers can be housed in and powered by a standard CAMAC crate.