Formation and evolution of a pair of collisionless shocks in counter-streaming flows

Abstract

A pair of collisionless shocks that propagate in the opposite directions are firstly observed in the interactions of laser-produced counter-streaming flows. The flows are generated by irradiating a pair of opposing copper foils with eight laser beams at the Shenguang-II (SG-II) laser facility. The experimental results indicate that the excited shocks are collisionless and electrostatic, in good agreement with the theoretical model of electrostatic shock. The particle-in-cell (PIC) simulations verify that a strong electrostatic field growing from the interaction region contributes to the shocks formation. The evolution is driven by the thermal pressure gradient between the upstream and the downstream. Theoretical analysis indicates that the strength of the shocks is enhanced with the decreasing density ratio during both flows interpenetration. The positive feedback can offset the shock decay process. This is probable the main reason why the electrostatic shocks can keep stable for a longer time in our experiment.

Full particle-in-cell simulation of the interaction between two plasmas for laboratory experiments on the generation of magnetized collisionless shocks with high-power lasers

“…Collisionless shocks play important roles in the generation of high-energy particles in various situations, which is one of the most important outstanding issues in plasma physics. 1,2 Recently, laboratory experiments using highpower lasers are conducted on the generation of collisionless shocks propagating into unmagnetized [3][4][5][6] and magnetized [7][8][9][10][11] plasmas. In particular, the laboratory experiments of magnetized collisionless shocks are of great interest since the most astrophysical and solar-terrestrial plasmas hosting the collisionless shocks are magnetized.…”

Electron stochastic acceleration in laboratory-produced kinetic turbulent plasmas

“…Optical diagnostics is widely used in laboratory astrophysics studies 17 , 43 , 44 , here, we use it to measure the self-generated magnetic fields, plasma density, and filament structures. As shown in Supplementary Fig.…”

Status and development of high-power laser facilities at the NLHPLP

“…These facilities can be operated independently or combined to support extensive experimental capabilities. Accordingly, this platform is of great significance to interested scientists worldwide, providing various physical experiments, such as fast ignition [25,26] (eight beams used for pre-compression and a picosecond PW beam used for ignition), indirectdrive physics [29][30][31][32] , direct-drive physics [21] , laboratory astrophysics (collisionless shocks) [23,28,[33][34][35][36] , equation of state [24,37] , HED physics [27,38] , and diagnostic instruments development [24,[39][40][41] . Each facility is equipped with a basic set of diagnostics, including a spectrometer (X-ray, visible, and UV), streaked slit camera (X-ray and visible), near backscatter imager, energy disperse spectroscopy (electron/ion/proton), nuclear track analysis system, and neutron angular distribution detector.…”

“…In addition, the SG-II 5 PW facility [19] , as an extreme light source, is under construction and the prior two optical parametric amplifiers have been accomplished. All of the present running facilities constitute an open multifunctional platform [20] , and many important achievements [21][22][23][24][25][26][27][28] , especially for target physics in ICF research, were witnessed in a series of experiments on this platform.…”