Simulation Of Electron Acceleration And Terahertz Radiation Driven By Laser Interaction With Gas Target

When the laser interacts with the plasma,the mass force of the laser first drives the electrons to move,which generates the charge separation field in the plasma,also known as the wake field wave.Tail wave field of the electric field gradient can be as high as 100 Ge V than a conventional accelerator acceleration for three to four orders of magnitude higher than that of gradient,the centimeter scale can be put into an acceleration to Ge V energy,therefore,based on the mechanism of laser plasma wave acceleration,is expected to develop mesa small electronic accelerator and radiation sources,thus reducing the production cost,greatly improve its range of application.High energy electrons can radiate rays of different energies,such as THz rays,X rays and gamma rays,by rotating motion.These rays of different energies have a wide range of applications in industrial and medical fields,such as nondestructive testing of materials,industrial flaw detection and medical diagnosis.In this paper,we mainly study the plasma wake structure and electron acceleration generated by the interaction between a strong laser and a gas target.Since the high-energy electron radiation is also related to the electron lateral oscillation amplitude,the electron energy and the electron lateral oscillation amplitude are paid more attention.By exploring the characteristics of high-energy electron cyclotron radiation,the interaction mode between laser and gas target is designed to improve electron energy and electron lateral oscillation amplitude.The dynamic particle simulation method(PIC)is used to simulate the design of a gas target for the combination of nitrogen and helium,in which the helium part is a channel with a parabolic density distribution.A linearly polarization laser with a wavelength of 800nm and an intensity of 1x10¹⁹W/cm² is selected to carry out parameter scanning on the density of helium plasma.It is found that when the density of helium plasma is 0.0018n_c,the electron gets the maximum energy,which reaches 520Me V,but the transverse oscillation amplitude of the electron is only 1 micron.Furthermore,the laser off-axis incident gas target is used to increase the electron lateral oscillation amplitude,and the parameter scanning of the off-axis deviation is carried out.It is found that when the off-axis deviation is 5 microns,the electron lateral oscillation amplitude reaches 2.5 microns,while the electron energy does not decrease.The simulation results show that off-axis laser incident is beneficial to increase the electron lateral oscillation amplitude,thus increasing the radiation energy.The terahertz damped radiation in the linear wake wave is studied.The calculation shows that the terahertz radiation is concentrated in a small cone centered on the laser axis,and the peak energy deviates from the laser axis,which is related to the thickness of the plasma.