The first laboratory observation of transition from electrostatic toward electromagnetic collisionless shocks in laser driven plasmas

There exists a set of conditions where electrostatic collisionless shocks are unstable to streaming instabilities causing the generation and amplification of magnetic fields. Given the right conditions, the streaming instabilities can produce an electromagnetic shock. Previous theoretical and simulation work has explored this transition. In this presentation, we present the first experiment to access this physical process. A CH supersonic plasma flow collides with a hydrogen gas jet gas puff to create an electrostatic collisionless shock at the OMEGA laser facility. Imaging 2ω Thomson scattering, D³He backlit proton radiography, and electron spectroscopy diagnose the shock. Thomson scattering measurements show density and temperature jumps from the shock and prove low collisionality. Proton radiographs and associated reconstructions show a strong shock electrostatic potential early in time. Later in time, this potential decays away into a turbulent-like structure. Filamentation structures due to the beam-Weibel instability emerge and increase in wavelength with time. Electron spectroscopy data show the acceleration of electrons with a high energy power-law tail, a signature of electromagnetic shocks. PIC simulations show the formation of an electrostatic shock and the generation of magnetic fields due to instabilities. In total, these data show an electrostatic shock decaying and transitioning toward an electromagnetic shock.