High-power laser experiments to study collisionless shock generation

Abstract

Abstract.A collisionless Weibel-instability mediated shock in a self-generated magnetic field is studied using two-dimensional particle-in-cell simulation [Kato and Takabe, Astophys. J. Lett. 681, L93 (2008)]. It is predicted that the generation of the Weibel shock requires to use NIF-class high-power laser system. Collisionless electrostatic shocks are produced in counter-streaming plasmas using Gekko XII laser system [Kuramitsu et al., Phys. Rev. Lett. 106, 175002 (2011)]. A NIF facility time proposal is approved to study the formation of the collisionless Weibel shock. OMEGA and OMEGA EP experiments have been started to study the plasma conditions of counter-streaming plasmas required for the NIF experiment using Thomson scattering and to develop proton radiography diagnostics.

Radiation from particles moving in small-scale magnetic fields created in solid-density laser-plasma laboratory experiments

“…Rather, proton-radiography or Thomson scattering, via the injection of external particles, is the prescribed diagnostic tool. 27,28 In principle, the sub-Larmor-scale ions should emit Weibler radiation, but this will be orders of magnitude less intense (because of their higher mass) than the radiation produced by electrons via alternative radiation mechanisms. In addition, plasma dispersion would certainly screen out any ion Weibler radiation, since the characteristic emission frequencies will be well below the electron plasma cutoff frequency.…”

“…23,[27][28][29][30] This is achieved via weaker laser intensities and longer pulse durations ($10 14 W/cm 2 and $1 ns, for a recent Omega laser experiment)-although higher intensities are believed to be required for the creation of a shock. 27,28 Recently, the formation of filamentary structures indicative of ion-driven Weibel-like magnetic fields has been observed in a scaled laboratory experiment at the Omega Laser Facility. [28][29][30] Electrons moving in small-scale magnetic turbulence emit radiation that is distinct from both synchrotron and cyclotron radiation.…”

“…It is strongly believed that presently existing laser facilities, such as OMEGA/OMEGA EP and NIF, will eventually observe these Weibel-mediated shocks in the laboratory, i.e., to make a "gamma-ray burst in a lab" [24][25][26] . In contrast to the aforementioned solid-density plasmas, these plasmas flow freely inbetween laser ablated metal plates 23,[27][28][29][30] . This is achieved via weaker laser intensities and longer pulse durations (∼ 10 14 W/cm 2 and ∼ 1 ns, for a recent Omega laser experiment) -although higher intensities are believed to be required for the creation of a shock 27,28 .…”

“…In contrast to the aforementioned solid-density plasmas, these plasmas flow freely inbetween laser ablated metal plates 23,[27][28][29][30] . This is achieved via weaker laser intensities and longer pulse durations (∼ 10 14 W/cm 2 and ∼ 1 ns, for a recent Omega laser experiment) -although higher intensities are believed to be required for the creation of a shock 27,28 . Recently, the formation of filamentary structures indicative of ion-driven Weibel-like magnetic fields have been observed in a scaled laboratory experiment at the Omega Laser Facility [28][29][30] .…”

Collisionless electrostatic shock generation using high-energy laser systems

“…Possibility of an experiment with high-energy laser has been discussed, and found that high-density (electron density ∼10 20 cm −3 ) and high-flow velocity (∼1000 km/s) plasmas are required to produce collisionless Weibel shock [58,59]. In order to achieve these plasma parameters, a highenergy laser system with an energy of >hundreds of kJ or the world largest laser, the National Ignition Facility (NIF) laser (LLNL, U.S.A), is required [58,59].…”