Laboratory astroparticle physics

Abstract:

We present a proposal for testing the prediction of non-equilibrium quantum field theory below the Schwinger limit. The proposed experiments should be able to detect a measurable number of gamma rays resulting from the annihilation of pairs in the focal spot of two opposing high intensity laser beams. We discuss the dependence of the expected number of gamma rays with the laser parameters and compare with the estimated background level of gamma hits for realistic laser conditions.

Abstract:

We investigate ultrafast (fs) electron dynamics in a liquid hydrogen sample, isochorically and volumetrically heated to a moderately coupled plasma state. Thomson scattering measurements using 91.8 eV photons from the free-electron laser in Hamburg (FLASH at DESY) show that the hydrogen plasma has been driven to a nonthermal state with an electron temperature of 13 eV and an ion temperature below 0.1 eV, while the free-electron density is 2.8x10{20} cm{-3}. For dense plasmas, our experimental data strongly support a nonequilibrium kinetics model that uses impact ionization cross sections based on classical free-electron collisions.

Abstract:

An experiment designed to launch laser-ablation-driven shock waves (10 to 70 Mbar) in a planar liquid-deuterium target on the OMEGA Laser System and to diagnose the shocked conditions using inelastic x-ray scattering is described. The electron temperature (Te) is inferred from the Doppler-broadened Compton-downshifted peak of the noncollective (αs = 1kλD > 1) x-ray scattering for Te > T Fermi. The electron density (ne) is inferred from the downshifted plasmon peak of the collective (αscatter > 1) x-ray scattering. A cylindrical layer of liquid deuterium is formed in a cryogenic cell with 8-μm-thick polyimide windows. The polyimide ablator is irradiated with peak intensities in the range of 1013 to 10 15 W/cm2 and shock waves are launched. Predictions from a 1-D hydrodynamics code show the shocked deuterium has a thickness of ∼0.1 mm with spatially uniform conditions. For the drive intensities under consideration, electron density up to ∼5 × 1023 cm -3 and electron temperature in the range of 10 to 25 eV are predicted. A laser-irradiated saran foil produces Cl Ly αemission. The spectrally resolved x-ray scattering is recorded at 90° for the noncollective scattering and at 40° for the collective scattering with a highly oriented pyrolytic graphite (HOPG) crystal spectrometer and an x-ray framing camera. © 2010 IOP Publishing Ltd.