MODELING SUPERSONIC-JET DEFLECTION IN THE HERBIG–HARO 110-270 SYSTEM WITH HIGH-POWER LASERS

First Inertial Confinement Fusion Implosion Experiment in Octahedral Spherical Hohlraum

In inertial confinement approaches to fusion, the asymmetry of target implosion is a major obstacle to achieving high gain in the laboratory. A recently proposed octahedral spherical hohlraum makes it possible to naturally create spherical target irradiation without supplementary symmetry control. Before any decision is made to pursue an ignition-scale laser system based on the octahedral hohlraum, one needs to test the concept with the existing facilities. Here, we report a proof-of-concept experiment for the novel octahedral hohlraum geometry on the cylindrically configured SGIII laser facility without a symmetry control. All polar and equatorial self-emission images of the compressed target show a near round shape of convergence ratio 15 under both square and shaped laser pulses. The observed implosion performances agree well with the ideal spherical implosion simulation. It also shows limitations with using the existing facilities and adds further weight to the need to move to a spherical port geometry for future ignition laser facilities.

Novel Target Designs to Mitigate Hydrodynamic Instabilities Growth in Inertial Confinement Fusion

High density carbon (HDC) ablator is one of the promising candidates toward thermonuclear ignition in inertial confinement fusion (ICF), but it shows the largest ablation front instability growth as compared to other traditional ablator materials. In this Letter, we propose a novel HDC-CH capsule design, opening the way to mitigate the hydrodynamic instabilities by using CH as the outermost ablator layer, while keeping HDC as the main ablator for maintaining the advantage of short laser pulses. The CH layer is completely ablated during the shock transit phase. In the HDC-CH design, it is the first shock reflected from the HDC/CH interface that meets the ablation front first, which reduces the ablation front growth factor by about one order of magnitude at peak implosion velocity due to the Richtmyer-Meshkov and the Rayleigh-Taylor instabilities. Our 2D simulation studies demonstrate convincingly that the ablation front growth factor of the HDC-CH capsule can be significantly reduced at both the end of shock transit phase and the time at peak implosion velocity, as compared to a HDC capsule. This novel HDC-CH capsule not only keeps the main advantage of the HDC ablator, but also has the advantage of low hydrodynamic instabilities, which can provide a larger margin toward ICF ignition. It can be applicable to both indirect-drive and direct-drive targets.

Laboratory Study on Disconnection Events in Comets

When comets interacting with solar wind, straight and narrow plasma tails will be often formed. The most remarkable phenomenon of the plasma tails is the disconnection event, in which a plasma tail is uprooted from the comet's head and moves away from the comet. In this paper, the interaction process between a comet and solar wind is simulated by using a laser-driven plasma cloud to hit a cylinder obstacle. A disconnected plasma tail is observed behind the obstacle by optical shadowgraphy and interferometry. Our particle-in-cell simulations show that the difference in thermal velocity between ions and electrons induces an electrostatic field behind the obstacle. This field can lead to the convergence of ions to the central region, resulting in a disconnected plasma tail. This electrostatic-field-induced model may be a possible explanation for the disconnection events of cometary tails.