Accounting for Spontaneous Charge Production in the EMCCD Gain Register
Abstract:
An electron-multiplying charge-coupled device (EMCCD) is often used for taking images with space telescopes and other devices. Photons hit the pixels and photo-electrons are created, and these are multiplied via impact ionization as they travel through the gain register from one gain stage to the next. A high gain means a high multiplication factor, and this is achieved through a high voltage difference across a gain stage. If the gain is high enough, the chance of spontaneous charge production increases. The probability distribution function governing the gain process in the literature only accounts for charge multiplication if one or more electrons enters the gain register. I derive from first principles the modified probability distribution that accounts for spontaneous charge production. I also examine some high-gain EMCCD data and show through maximum likelihood estimation that the data conform better to the modified distribution versus the usual one in the literature. The use of the modified distribution would in principle improve the accuracy of signal extraction from a frame.
