First experimental comparisons of laser-plasma interactions between spherical and cylindrical hohlraums at SGIII laser facility

Abstract

We present our recent laser-plasmas instability (LPI) comparison experiment at the SGIII laser facility between the spherical and cylindrical hohlraums. Three kinds of filling are considered: vacuum, gas-filling with or without a capsule inside. A spherical hohlraum of 3.6 mm in diameter, and a cylindrical hohlraum of 2.4 mm × 4.3 mm are used. The capsule diameter is 0.96 mm. A flat-top laser pulse with 3 ns duration and up to 92.73 kJ energy is used. The experiment has shown that the LPI level in the spherical hohlraum is close to that of the outer beam in the cylindrical hohlraum, while much lower than that of the inner beam. The experiment is further simulated by using our 2-dimensional radiation hydrodynamic code LARED-Integration, and the laser back-scattering fraction and the stimulated Raman scatter (SRS) spectrum are post-processed by the high efficiency code of laser interaction with plasmas HLIP. According to the simulation, the plasma waves are strongly damped and the SRS is mainly developed at the plasma conditions of electron density from 0.08 nc to 0.1 nc and electron temperature from 1.5 keV to 2.0 keV inside the hohlraums. However, obvious differences between the simulation and experiment are found, such as that the SRS back-scattering is underestimated, and the numerical SRS spectrum peaks at a larger wavelength and at a later time than the data. These differences indicate that the development of a 3D radiation hydrodynamic code, with more accurate physics models, is mandatory for spherical hohlraum study.

Interaction of parametric instabilities from 3ω and 2ω lasers in large-scale inhomogeneous plasmas

“…Thus, the particular profiles of different species plasmas will be formed along the path of an inner-ring laser propagation. Chen et al researched the parametric instabilities in gas-filled hohlraums with a capsule, and compared the simulated results with experimental data in the SGIII laser facility [21]. They found that the plasma waves were strongly damped and the SRS was mainly developed at plasma conditions of electron density from 0.08n c to 0.1n c .…”