Diffusion and kinetic energy of electrons accelerated by focused few-cycle azimuthally polarized pulses

Using the model of the focused few-cycle azimuthally polarized ultrashort pulses based on the complex sink-source method, the electron acceleration by the pulses is studied. Under the same peak intensity and beam waist width, the maximum exit kinetic energy of electrons will be increased with the increase of the time domain widths of the pulses. Then, with the further increase of the pulse time domain widths, the maximum exit kinetic energy of the electron will be slowly decreased. The diffusion angle of the electron beam can be as small as 2° and changes little with the carrier envelope phase of the pulse. When the carrier envelope phase is changed, the diffusion angle of the electron beam is reduced by more than 1 order of magnitude with the increase of the time domain widths of the pulses. For the first time, to the best of our knowledge, we found that, by choosing the pulse with the appropriate time domain width, an electron beam with a small diffusion angle and high kinetic energy can be obtained at the same time. When the pulse duration is increased, the radiation spectrum of the acceleration radiation is found to undergo a significant redshift for the first time. These studies can be applied in the fields of high-energy physics experiments, medicine, material detection, and others.