In indirect-drive inertial confinement fusion, kinetic effects at the gold-gas interface alter temperature and density distributions, impacting laser propagation and hohlraum energetics^[1,2]. High-density gold plasma drives electrostatic shocks in gas, with interfacial  electric field reflecting upstream ions to tens of keV. We injected a 1:1 hydrogen-deuterium gas mixture onto a gold planar target surface and measured ion energy spectra along the target normal direction^[3]. The experiments revealed peak velocities of approximately 1500 km/s for hydrogen ions and 1100 km/s for deuterium ions. Based on hybrid simulations Ascent-H, we attribute this disparity to the complex electric field structures during the underdeveloped shock formation stage. The simulations demonstrate that electrostatic shocks become more fully developed with increasing initial upstream electron density^[4]. Additionally, proton radiography measurements were employed to map the interfacial electric field distribution. These advancements provide crucial insights into the underlying physics of inertial confinement fusion.
 

1. Shan, L.Q., Cai, H.B., Zhang, W.S., et al. Experimental evidence of kinetic effects in indirect-drive inertial confinement fusion hohlraums. Physical Review Letters 120(19), 195001 (2018)
2. Zhang, W.-S., Cai, H.-B., Shan, L.-Q., et al. Anomalous neutron yield in indirect-drive inertial-confinement-fusion due to the formation of collisionless shocks in the corona. Nuclear Fusion 57(6), 066012 (2017)
3. Yuan Zongqiang, Deng Zhigang, Teng Jian, et al. Geant4 simulations of measurement of energy spectra of reflected ions generated by nanosecond-laser-drive non-relativistic collisionless electrostatic shocks. High Power Laser and Particle Beams, 2022, 34: 122005.
4. Yuan Zongqiang, Zhang xu, Yao peilin et al. Experimental diagnosis of high-speed ions at the gold bubble/gas interface (Manuscript in preparation).

inertial confinement fusion, high-speed ions, bubble/gas interaction, ion acceleration