61 / 2020-02-27 23:00:07

Shock Ignition Related Study of Hot Electron Generation via Advanced X-ray spectroscopy and Time Resolved Imaging

Shock ignition; Laser driven suprathermal electrons; X-ray plasma diagnostics

全体主题 > 激光和粒子束聚变

Despite generally acknowledged importance of the hot electron (HE) role in a development of shock ignition (SI) approach to inertial confinement fusion, the detailed mechanisms of their generation and impact on formation and dynamics of strong shocks are not fully understood yet. New theoretical approaches that allow complex treatment of parametric instabilities, HE generation, and energy deposition resulted in advancements of numerical codes which need reliable experimental data for their verification.
We resume the results of time integrated x-ray spectroscopic investigation of HE generation based on a combination of the high spectral and spatial resolution with the extremely large dispersion of the vertical geometry Johann spectrometer [1] and compare them with time resolved measurements performed at the Prague facility PALS. The latter experimental setup combines the spherically bent crystal of quartz (422) with the x-ray streak camera to obtain magnified time resolved monochromatic images of K-shell emission due to the HE action in laser irradiated Cu targets. By using a single laser beam (wavelength 1.315 μm, pulse duration 0.3 ns, focal spot size 100 μm), the bare or plastic coated Cu targets were irradiated at intensities up to 1.5×1016 W/cm2. The recorded x-ray images provide information on temporal profiles of the HE generation, their lateral spread and energy deposition inside the targets. The observed dependencies of the duration, relative delay vs the laser beam maximum, and integrated Cu Kα emissivity are discussed with respect to alternate mechanisms of the HE production.
The experimental data are complemented by hydrosimulations performed with the FLASH code and kinetic simulations with the EPOCH code. The results obtained contribute to a development of advanced methods for HE diagnosis at shock ignition relevant conditions.