Intense Relativistic Electron Beam Interaction With A Two-Pulse Radiography Converter

摘要

Summary form only given. The interaction of a relativistic electron beam pulse (typical 20 MeV, 2 kA, 60 ns, 1 mm radius) with a Bremsstrahlung converter is numerically investigated in the context of two-pulse x-ray radiography. In such experiment, two short and intense pulses of electrons, about 1 μs delayed, create x-ray pulses to image a dynamic object at different times. Due to the high energy density deposited by the first pulse, the converter is partially ablated and surrounded by a plasma plume at the second electron pulse arrival [1]. The energy deposition of the electron beam in millimeter-sized converters is calculated by the Monte Carlo, muliparticle transport code DIANE developed at CEA. The subsequent converter material expansion is calculated by the CEA 3D hydrodynamic code HESIONE using a multiphase equation of state. The temperature in the target rises to few eV and to pressure to ~ 1 Mbar, which induces a fast expansion. The transverse flow of material decreases the mass converted interacting with the second electron pulse, whick is detrimental to the Bremsstrahlung yield. Another consequence of the converter ablation concerns the second electron pulse propagation through the centimeter-sized plasma plume which could lead to a variation of the X-ray source. We report on our theoretical and numerical work to describe these phenomena, and the desing of some key experiments aimed to test and validate our calculations.