Variations of implosion asymmetry with hohlraum length and time in indirect-drive inertial confinement fusion

Abstract

In order to achieve the high density compression in laser indirect-drive inertial confinement fusion, the implosion symmetry and hohlraum radiation uniformity are strictly required. To study the variations of implosion asymmetry with hohlraum length and time, three kinds of hohlraum lengths are adopted in experiment. X-ray emission from capsule fuel is measured by an X-ray framing camera. Based on measured capsule compression process and ellipticity variation, it is preliminarily judged that the medium hohlraum of 1700 μm long is the closest to implosion symmetry demand of Shenguang Ⅲ prototype laser facility. Time-resolved implosion asymmetry is derived from a simplified analytic model, in which used is the time-resolved hohlraum radiation nonuniformity derived from a view-factor code. The derived results of the time-resolved implosion asymmetry are basically in agreement with experimental results. The physical mechanism for how hohlraum radiation nonuniformity evolution induces the variations of implosion asymmetry with hohlraum length and time is analyzed.

First integrated implosion experiments on the SG-III laser facility

“…It has 8 driving laser beams with the same incident angles which are the same as SG-II laser, and it also has a backlight beam (or a Thomson scattering probe beam). The hohlraum energetics [8][9][10], radiation uniformity [11], LPI [12][13][14], planar RT instability [15,16] and integrated implosion performance [17] were studied on the SG-III prototype platform. For the integrated implosion experiments using 1 ns squared pulse, the YOC reached 70% when the implosion was dominated by shock compression, and it decreased to about 5% when the shell thickness was increased and the implosion was dominated by inertial compression at the convergence-ratio similar to that on SG-II.…”