Investigating the hohlraum radiation properties through the angular distribution of the radiation temperature

Abstract

The symmetric radiation drive is essential to the capsule implosion in the indirect drive fusion but is hard to achieve due to the non-uniform radiation distribution inside the hohlraum. In this work, the non-uniform radiation properties of both vacuum and gas-filled hohlraums are studied by investigating the angular distribution of the radiation temperature experimentally and numerically. It is found that the non-uniform radiation distribution inside the hohlraum induces the variation of the radiation temperature between different view angles. The simulations show that both the angular distribution of the radiation temperature and the hohlraum radiation distribution can be affected by the electron heat flux. The measured angular distribution of the radiation temperature is more consistent with the simulations when the electron heat flux limiter fe=0.1. Comparisons between the experiments and simulations further indicate that the x-ray emission of the blow-off plasma is overestimated in the simulations when it stagnates around the hohlraum axis. The axial position of the laser spot can also be estimated by the angular distribution of the radiation temperature due to their sensitive dependence. The inferred laser spot moves closer to the laser entrance hole in the gas-filled hohlraum than that in the vacuum hohlraum, consisting with the x-ray images taken from the framing camera. The angular distribution of the radiation temperature provides an effective way to investigate the hohlraum radiation properties and introduces more constraint to the numerical modeling of the hohlraum experiments.

An improved view-factor method including plasma filling for angular distribution of radiation temperature from a laser-driven hohlraum

“…In particular, the calculations become much lower than the experiments with the increase of time. The calculations with ERV show reasonable agreement with the measurements of all angles within the ±3% accuracy of the experimental observation [18,54,57]. It merits mentioning that the plasma filling has slight impact on the radiation temperature from the U42.…”

“…These deviations indicate that it is necessary to investigate the radiation distribution inside the hohlraum from multi-angle detection, which conduces to understand the hohlraum radiation properties and ensure that the radiation drive on the capsule could be more correctly inferred from the DANTE or FXRDs measurement [18].…”

Summary of laser plasma physics sessions at the first AAPPS-DPP conference

“…The invited talk by Yang [L-I24] reported an experimental investigation on the hohlraum radiation properties through the angular distribution of the radiation temperature performed on the SG-III prototype in Mianyang. Comparison between the experimental observations and the two-dimensional radiationhydrodynamic simulations was carried out (Zhang et al 2014(Zhang et al , 2016aHao et al 2014;Yang et al 2014). The difference between the 2D simulations and the real 3D effects caused by limited beam numbers on SG-III prototype laser facility was considered, and the influence of power balance and pointing accuracy of laser beams on the measured results was evaluated.…”