The Role Of Pulsed High Current Electron Beam, The Next Time The Target Ejecta Speed Measurement,

The interaction of the focused 20MeV, 2.5 kA, 60 ns electron beam (FWHM spot size 1.5mm) with the tantalum converter target produces back-ejecta target material, which results in the discharge of the accelerator module and influences the everyday operation. At present, the shutter is considered maybe a useful and feasible way to block off the back-ejecta target material, and the shutting time of the shutter is decided by the velocity of the back-ejecta target material.As LIA is developed from single pulse to multi-pulse nowadays, the importance of how to improve the design of the converter target to make each pulse produce desired X-ray must be considered. The long target plasma channel created by preceding pulses may make the incoming electron beam unstable and expand the final spot size as well as the backstreaming ions which consist of contaminant ions and target material ions. In addition, the beam-target interaction will vaporize and disperse the target material rapidly, which may result that there is not enough target material to produce enough X-ray dose with the incoming beam.The observation and measurement of the beam-target interaction area under strong electromagnetic and radial interference is probed in this paper. The phenomenon of the beam-target interaction is observed for the first time through fast photography, and the experimental result shows that the axial velocity of back ejecta target material is faster than 2.9mm/μs. In the theoretical research, the electron beam's energy deposition in different tantalum target is simulated by the Monte-Carlo program MCNP, on the basis of which the vaporized target material's dynamics is simulated by solving the series of Euler equations for mass, momentum and energy respectively, and we reach a velocity of 9.7mm/μs under the ideal conditions. According to the simulation and experimental result, the elementary mechanism of destruction of the different tantalum targets bombarded by the high intensity current pulse electron beam is presented. The progress of destruction and some phenomena in the experiment are explained.