Simulation on distributed target material impacted by high intensity current multi-pulse electron beam

The bremsstrahlung and energy deposition of multi-pulse high intensity relativistic electron beam injecting into multi-layer tantalum-graphite target are investigated. The energy deposition is calculated by Geant4 code, and the bremsstrahlung by fundamental radiation theory and Monte-Carlo method. The calculated results show the energy deposition in the hotspot of each layer decreases. The emittance and the radial distribution of the bremsstrahlung and electron beam are mostly affected by the tantalum layers. The low energy deposition rate and high heat capacity of graphite layers can improve the thermodynamic properties of the target. For a single pulse, at the tantalum-graphite thickness ratio 1∶1, the graphite can absorb all heat deposition of the neighboring tantalum layers, and the bremsstrahlung efficiency is 35.4%. With 4 pulses, the ratio should be 1∶13, and the total bremsstrahlung efficiency decreases to 19.9%. Considering the requirement of bremsstrahlung X-ray quantity and quality, the total thickness of tantalum should be 1.2 mm if the Ta-C thickness ratio is 1∶5, and 0.7 mm if the ratio is 1∶10.