Optimum event rate for a CCD detector

Abstract

A simple event-counting technique is considered that can be implemented on detector systems with adjustable exposure times. A single measurement cycle has two steps: exposure and readout. During readout a threshold is used to discriminate against background noise, making it impossible to differentiate between single or multiple events. The actual event rate can be estimated by accumulating the results of repeated measurement cycles, and applying a correction based on the probability for multiple events to occur. By considering the uncertainty in the estimation of the event rate, and assuming a Poisson process, it is shown that optimum exposure requires an average event count per exposure of roughly 1.7. The technique is applied to a high-energy electron-counting system based on a linear CCD photodetector.