A nanosecond relativistic high-current electron beam as a tool for materials processing

The results of investigations on the formation of a relativistic high-current electron beam with a SINUS-7 accelerator and its application to the materials modification are presented in the paper. The maximum electron energy of the beam and pulse duration were 1.4 MeV and 50 ns, respectively. The current density at the center of the beam measured with a Faradey cup was found to be 7 kA/cm². The temperature and stress fields in the target induced by the electron beam irradiation were simulated with the BETAINI numerical code based on solving the hydrodynamic equations. It was numerically established that a stress wave is formed near the irradiated surface, which moves towards the rear side of the target with the amplitude being 7 GPa. The targets used were of different thicknesses (2-6 mm), which produced different spalled layer depths, on the order of magnitude of hundreds of microns. Thus, the depth of the spalled layer is shown to depend on the thickness of the target with the dependence being directly proportional for these. Based on experiments and calculations the spalled strength of copper was determined being 1.3 GPa at a strain rate of 5×10⁵ s^-1. Scanning electron microscopy of the spalled surface was also carried out.