High-Mach number collisionless shock and photo-ionized non-LTE plasma for laboratory astrophysics with intense lasers

Abstract

We propose that most of the collisionless shocks in the Universe, for example, supernova remnant shocks, are produced because of the magnetic field generated by Weibel instability and its nonlinear process. In order to verify and validate the computational result confirming this theory, we are carrying out model experiments with intense lasers. We are going to make a collisionless counter-streaming plasma with intense laser ablation based on the scaling law to laser plasma with the particle-in-cell simulation resulting in Weibelmediated shock formation. Preliminary experimental data are shown. The photo-ionization and resultant non-LTE plasma physics are also very important subjects in astrophysics related to mainly compact objects, for example, black hole, neutron star and white dwarf. Planckian radiation with its temperature 80-100 eV has been produced in gold cavity with irradiation of intense lasers inside the cavity. The sample materials are irradiated by the radiation inside the cavity and absorption and self-emission spectra are observed and analyzed

Collisionless shockwaves formed by counter-streaming laser-produced plasmas

“…The generation of collisionless shockwaves has been studied in our work (Kato and Takabe 2008;Takabe et al 2008) and other groups' previous work (Forslund and Shonk 1970, Mason 1972) with particle-in-cell simulations. The results show that two types of instabilities can generate collisionless shockwaves in counter-streaming plasmas.…”

Filamentation Instability of Counterstreaming Laser-Driven Plasmas

“…Due to the long mean-free-path between ions in opposing streams, the streams interpenetrate, establishing supersonic counterstreaming conditions in the ion populations, while the electrons form a single thermalized cloud. Meanwhile, the plasma density is also sufficient so that the the ion skin depth d i = (m i /µ 0 ne 2 ) 1/2 , is much smaller than the system size L. These conditions allow the growth of an ion-driven Weibel instability, for which d i is the characteristic wavelength [14][15][16]. The Weibel-generated electromagnetic fields were observed with an ultrafast pro- ton radiography technique [17], and identified through good agreement with analytic theory [6] and particle-incell simulations, discussed below.…”

High-power laser experiments to study collisionless shock generation

“…Recent numerical and PIC simulation studies show that there are two possible collisionless shocks in unmagnetized plasmas: One is an electrostatic (ES) shock [1,2], and the other is a Weibel-instability mediated shock in self-generated magnetic field [3,4].…”