Studying Electromagnetic Beam Instabilities in Laser Plasmas for Alfv´enic Parallel Shock Formation

We present measurements of the collisionless interaction between an exploding laser-produced plasma (LPP) and a large, magnetized ambient plasma. The LPP is created by focusing a high energy laser on a target embedded in the ambient Large Plasma Device (LAPD) plasma at the University of California, Los Angeles. The resulting super-Alfv´enic (MA = 5) ablated material moves parallel to the background magnetic field (300 G) through 12m (80 δi) of the LAPD, interacting with the ambient Helium plasma (ni = 9×1012 cm−3) through electromagnetic beam instabilities. The debris is characterized by Langmuir probes and a time-resolved fluorescence monochromator. Waves in the magnetic field produced by the instabilities are diagnosed by an array of 3-axis ‘bdot’ magnetic field probes. Measurements are compared to hybrid simulations of both the experiment and of parallel shocks.