Theoretical calculation of CsI photocathode’s response sensitivity of soft X-ray streak camera

CsI photocathode's response sensitivity is an important parameter for the quantitative diagnosis of X-ray spectroscopy by soft X-ray streak camera, and its theoretical calculation has important guiding significance. The current theoretical analytical model are based on the one-dimensional random walking model of secondary electrons generated by thin film photocathodes, including the Henke model under the condition of normal incidence of X-rays and energy greater than 1keV, and the Fraser model under variable angle incidence and photocathode thickness greater than 100nm, which have certain limitations. In this paper, the basic expression of the probability of secondary electron transmission are introduced, and the general expression of the response sensitivity of CsI photocathode are deduced in a larger parameter range (X-ray energy 0.1-10keV, photocathode thickness 10-200nm) varies with X-ray energy E, photocathode thickness t, and the angle θ between X-ray and cathode surface. Finally, the theoretical calculation results of this paper are compare and discussed with the Henke model, Fraser model, literature data and experimental data on Beijing synchrotron radiation facility, which verifies the accuracy and universality of the computational model, and a theoretical reference is provided for the optimal design of CsI photocathode in high-time-resolution spectrometric quantitative measurement.