Plasma scale length effects on protons generated in ultra-intense laser–plasmas

The energy spectra of protons generated by ultra-intense (1020 W cm−2) laser interactions with a preformed plasma of scale length measured by shadowgraphy are presented. The effects of the preformed plasma on the proton beam temperature and the number of protons are evaluated. Two-dimensional EPOCH particle-in-cell code simulations of the proton spectra are found to be in agreement with measurements over a range of experimental parameter

Topical Issues for Particle Acceleration Mechanisms in Astrophysical Shocks

Particle acceleration at plasma shocks appears to be ubiquitous in the universe, spanning systems in the heliosphere, supernova remnants, and relativistic jets in distant active galaxies and gamma-ray bursts. This review addresses some of the key issues for shock acceleration theory that require resolution in order to propel our understanding of particle energization in astrophysical environments. These include magnetic field amplification in shock ramps, the non-linear hydrodynamic interplay between thermal ions and their extremely energetic counterparts possessing ultrarelativistic energies, and the ability to inject and accelerate electrons in both non-relativistic and relativistic shocks. Recent observational developments that impact these issues are summarized. While these topics are currently being probed by astrophysicists using numerical simulations, they are also ripe for investigation in laboratory experiments, which potentially can provide valuable insights into the physics of cosmic shocks.Comment: 13 pages, no figures. Invited review, accepted for publication in Astrophysics and Space Science, as part of the HEDLA 2006 conference proceeding

Time resolved, in situ, X-ray diffraction from laser shocked solids

SIGLEAvailable from British Library Document Supply Centre- DSC:D181920 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Laboratory plasma astrophysics simulation experiments using lasers

Laboratory astroplasma physics experiments advance both our astrophysics and plasma physics knowledge. Contemporary high-energy, high-power laser technology enables us to reproduce in the laboratory the conditions of temperature and pressure that are met in extreme stellar environments. The focus is on experiments designed to address key aspects of the plasma physics occurring in supernova remnants. In this approach, a plasma physics model of the astrophysical object is identified and then scaled, and applied to a laboratory experiment. This offers the possibility of detailed measurements, which can be repeated as the input conditions are altered. Results from a scaled experiment designed to address aspects of collisionless plasma interaction in a young supernova remnant are presented. This experimental study is based on the interaction of two millimetre-scale counter-streaming laser-produced plasmas, created from exploded thin plastic foils in an intense transverse magnetic field. The dynamics of the two plasmas and their interaction are studied with, and without, magnetic fields, through spatially and temporally resolved measurements of the electron density

Creation of a uniform high magnetic-field strength environment for laser-driven experiments

Measurement of magnetic fields generated by a high-energy, high-intensity laser-driven millimeter-scale Helmholtz coil target is reported. The magnetic field is derived from a reverse current that passes through two coils of 1.25-mm radius. A peak field of 7 T with a time decay of 17 ns is inferred from a series of induction coil measurements when the hot-electron temperature driving the reverse current is approximately ~15 keV. A simple model of the laser-driven Helmholtz coil target suggests how the target should be optimized to produce high-peak fields and indicates that peak magnetic fields above 100 T are accessible. This could lead to exciting experiments in laser-plasma physics, in particular, experiments related to laboratory astrophysics