Generation of a quasi-monochromatic x-ray via collision of electron with tightly focused laser pulses

The nonlinear Thomson backscattering process of electron under circularly polarized laser pulses is studied. The influence of the central collision position of the electron and laser pulses on the spectral characteristics of the scattered light is analyzed. The results show that the frequency broadening caused by doppler nonlinear frequency shift can be reduced and the monochromicity of the emitted light can be improved by adjusting the central collision position or the initial position of electron appropriately. At the same time, taking the requirements for the radiation intensity of scattered light into account, the optimal situation to generate quasi-monochromatic x-rays is presented. Besides, a scheme to increase the radiation energy of backscattered light by controlling the laser pulse width is proposed without changing the frequency band width. It provides a solution to overcome the problem that the radiation energy is too weak in the scheme of changing the initial position of electron. In addition, it was found that the interference fringes of the emitted light growing greatly as the pulse width increases.