Optimization of an electromagnetic generator for strong shocks in low pressure gas
Résumé
affiche P41 Accretion and ejection processes are key elements to predict the evolution of Young Star Objects (YSOs) and their feedback to the interstellar medium. The observational signature of accretion is correlated to the presence of a strong shock which forms when the matter from a circumstellar disk hits the photosphere of the star. In this context, laboratory plasma astrophysics is a powerful tool to study the dynamics of these hypersonic processes. In parallel with experimental studies of radiative shocks in moderate pressure Xenon, driven by high-power lasers (U. Chaulagain et al., this conf.), strong shocks in low pressure rare gases can be generated using a very different technique: an electromagnetic gun. A low-inductance high-voltage generator at the kJ level drives a high current pulse, peaking at 150 kA in a 1-μs risetime. The principles of plasma sheath formation and acceleration are presented and modeled with a lumped circuit. A parametric study of the generator, coupled to the moving plasma, is presented, leading to proposed optimized geometries. A passive optical diagnostic is used to measure the shock profile and speed (typ. 20 km/s). In order to pre-process other complementary diagnostics, detailed MHD simulations, using the GORGON code, give reference information for the plasma parameters of the moving ionized sheath. Work supported by DIM ACAVÎle-de-France region, Labex PLAS@PAR (ANR-11-IDEX-0004-02), Observatoire de Paris and UPMC university.