Research On EMCCD Multiplication Characteristic And Photon Count Imaging Strategy

EMCCD (Electron Multiplication Charge-Coupled Device) achieved the multiplication of photo-generated charge signals in all solid-state technology of devices by adopting the impact ionization mechanism, and the EMCCD imaging system can obtain high quality images with the cold finger is cooled with LN2in a Dewar. To study the charge multiplying characteristic of EMCCD, an ionization rate model is presented based on the impact-ionization theory. Aiming at two TI IMPACTRON EMCCD devices, we develop a multiplication model at low fields (E<2.0x105V/cm) using avalanche multiplication integral formula. A method is put forward to predict the amounts of signal passing through the multi-stage cascaded electron multiplication register containing a fixed-voltage gate, which is useful to adjust and correct the gain of EMCCD devices. The model is suitable for lower temperature environment, in which electron-multiplication technology can be applied to photon counting strategies.Through analyzing and discussing the photon’s signal and the noises’charges in the EMCCD in detail, we introduce the probability density model of the output value of the multiplication register of an EMCCD and the probability density model of three dominate noises of an EMCCD imaging system. In this paper, a program of Monte Carlo simulation which has been applied extensively in particle transfer is designed, to imitate output of the EMCCD in Photon Counting operation.By introducing the discrete photon response and Photon Counting application technology in EMCCD imaging, this paper reveals the methods and processes for Photon Counting, as well as the condition of photon counts. The best amplitude threshold by which the most readout noise events is cut is computed with simulations. A series of simulations are conducted with the photon flux ranging from0.001phton/pixel/frame to1phton/pixel/frame, and the fraction of real events counted, noise events counted and the SNR indicate that Photon Counting imaging is very suitable for low flux with the CIC (Clock In Charge) noise being reduced as less as possible, and coincidence loss will be more severe as the flux becomes higher, which spark that Photon Counting does not work any more. The research works of this thesis are supported by the Joint Fund of Astronomy of National Science Foundation of China (NSFC) and Chinese Academy of Sciences (CAS)(Grant No.10978013).