The 6th International Conference on Matter and Radiation at Extremes (ICMRE2023)

160 / 2023-04-14 23:21:40

Experimental study on the hohlraum energetics in view-factor “I”-raum

view-factor, I-raum, drive-deficit

Inertial Confinement Fusion Physics > Alternative ICF and pulsed power technology-I

  In indirect-drive inertial confinement fusion, multiple laser beams are converted to soft x-ray to implode the capsule in the center of a hohlraum. A critical issue for achieving ignition is the drive symmetry on the capsule. As the gold bubbles expand, the gold bubbles of outer rings may block the transmission of inner rings, which will lead to the degeneration of the drive symmetry. In order to avoid the outer gold bubbles blocking the inner rings, a peanut-like hohlraum (I-raum) is designed to increase the radius of the wall where the outer rings irradiate, which delays the time of the outer gold bubbles entering the inner channel.

  Pre-radiation hydrodynamic simulation shows that the driving radiation temperature (Tr) on the capsule is equivalent in both a I-raum and a cylindrical hohlraum (246eV vs 249eV). However, experiment shows that the driving Tr on the capsule in a I-raum is much lower than that in a cylindrical hohlraum (225eV vs 240eV). The I-raum has an additional 20% drive-deficit compared with the cylindrical hohlraum. To study the additional drive-deficit, experiment of hohlraum energetics were carried with view-factor I-raum and view-factor cylindrical hohlraum, which were truncated 1/3 on one side. Tr were measured from both the open end and the LEH end of the view-factor hohlraum. Experiment results show that the Tr from the open end of the view-factor I-raum does lower than that of the view-factor cylindrical hohlraum, which indicates that the pre-radiation hydrodynamic simulation overestimates the driving Tr on the capsule in a I-raum. According to the post analysis of scaling law of hohlraum energetics, the increase of the wall area leads to the decrease of the Tr in I-raum. In addition, laser spot motion and gold bubble expansion were also measured. Through this experiment, the reason of drive-deficit in I-raum is clarified, and the improvement of radiation hydrodynamic simulation is further promoted.