Individual photon counting using e2v L3 CCDs for low background astronomical spectroscopy

Abstract

Sensitive, photon counting array detectors have the potential to dramatically improve the sensitivity of space-based astronomical spectrographs. We present first results from a program evaluating e2v L3 electron-multiplying CCDs as photon counting arrays. We find that L3 CCDs function well as photon counters, and see no show stoppers for our target applications. These include both ground and space-based instruments. Although we do detect spurious charge exceeding the dark current floor of the CCD, we find that physical dark current in the multiplication register is a significant component. This finding is significant because dark current, unlike clock induced charge (another potential culprit), is a problem that CCD designers have solved before.