Previous work has demonstrated the use of a plasma mirror (PM), after a laser-plasma accelerator (LPA), for generating Compton gamma-rays by retro-reflecting the spent laser pulse into the just-accelerated electrons. Here, we investigate the use of a PM to stimulate Compton backscatter (CBS) by retro-reflecting a spent pulse from the Texas Petawatt (TPW) laser after it has driven a cm-scale, GeV LPA. A comparative analysis between the electron and CBS pointing and divergence reveals strong agreement, from shot-to-shot, suggesting a reliable, non-invasive extension for GeV-beam metrology. Our observations confirm the self-aligning PM method is scalable to GeV LPAs, while also suggesting a technique with unique advantages and a robustness that can potentially be exploited for investigations of nonlinear Compton backscatter from ultralow divergence, GeV electrons using the Texas Petawatt Laser.

Overview of progress in construction and testing of the laser systems of ELI-Beamlines, accomplished since 2015, is presented. Good progress has been achieved in construction of all four lasers based largely on the technology of diode-pumped solid state lasers (DPSSL). The first part of the L1 laser, designed to provide 200 mJ < 15 fs pulses at 1 kHz repetition rate, is up and running. The L2 is a development line employing a 10 J / 10 Hz cryogenic gas-cooled pump laser which has recently been equipped with an advanced cryogenic engine. Operation of the L3-HAPLS system, using a gas-cooled DPSSL pump laser and a Ti: sapphire broadband amplifier, was recently demonstrated at 16 J / 28 fs, at 3.33 Hz rep rate. Finally, the 5 Hz OPCPA front end of the L4 kJ laser is up running and amplification in the Nd:glass large-aperture power amplifiers was demonstrated.

We exploited the Faraday effect to imprint polarization shifts on a transverse probe that captured the structure of a GeV laser-plasma accelerator. Our measurements suggested a plasma bubble diameter approximate to 50.8 +/- 10.1 mu m.

We have built and implemented a time-resolved ellipsometry diagnostic for dynamic material properties experiments at Sandia National Laboratories. This diagnostic measures the complex dielectric value of a sample experiencing dynamic compression, with a time resolution of a few nanoseconds. We show and discuss the dynamic ellipsometry measurements taken from shock loading experiments on a gas gun. This work is relevant to geophysical materials at high pressure-temperature conditions.

Radiative shocks and blast waves are important in many astrophysical contexts, such as supernova remnant formation, cosmic ray production, and gamma ray bursts. Structure formation on radiative blast wave fronts in late-stage supernova remnants is expected to play a role in star formation via seeding of the Jeans instability. The origin of these structures is believed to be an instability described theoretically by Vishniac [1], which has been subject to continued numerical and experimental study. We report here on a series of experiments designed to examine the effect of magnetic fields on the Vishniac overstability. Preliminary results suggest that a strong transverse magnetic field appears to shift the overstability to longer wavelengths, which may have implications for gravitational star formation models. We present unmagnetized results from an experiment in progress which decomposes the spatial structure of the blast wave for quantitative analysis of magnetic and radiative effects. (C) 2017 Elsevier B.V. All rights reserved.

We present equation of state (EOS) measurements of solid-density copper heated to 5-10 eV. A copper sample was heated isochorically by hydrogen ions accelerated from an adjacent foil by a high intensity pulsed laser, and probed optically. The measured temperature and expansion are compared against simulations using the most up-to-date wide range EOS tables available.

We measure the range of plasma ions in cold cluster gases by using the Petawatt laser at the University of Texas-Austin. The produced plasma propagated in all directions some hitting the cold cluster gas not illuminated by the laser. From the ratio of the measured ion distributions at different angles we can estimate the range of the ions in the cold cluster gas. It is much smaller than estimated using popular models, which take only into account the slowing down of charged particles in uniform matter. We discuss the ion range in systems prepared near a liquid-gas phase transition. (C) 2017 Elsevier B.V. All rights reserved.