Laboratory astroparticle physics

Abstract:

X-ray spectra and conversion efficiencies of the laser-produced chlorine Ly- α and K- α line radiation have been investigated to develop X-ray probes for the collective scattering regime. The Ly- α radiation was produced by either smoothed or un-smoothed laser beams with nanosecond-long laser pulses yielding high conversion efficiencies of up to 0.3% sufficient for X-ray scattering measurements. However, the time-integrated measurements show a significant dielectronic satellite emission on the red wing of the primary Ly- α line which must be avoided to resolve the plasmon feature in the scattering spectra. We find no red wing emission features for ultra-short pulse laser produced K-α radiation. The bandwidth of ΔE/E = 2 × 10^-3 is suited for collective scattering, but the conversion efficiency falls short of the high values achieved for the Ly-α. These findings indicate that present laser-produced X-ray sources will restrict the choice of detectors and plasma conditions for collective X-ray scattering from dense plasmas.

Abstract:

High Mach number blast waves were created by focusing a laser pulse on a solid pin, surrounded by nitrogen or xenon gas. In xenon, the initial shock is strongly radiative, sending out a supersonic radiative heat wave far ahead of itself. The shock propagates into the heated gas, diminishing in strength as it goes. The radiative heat wave also slows, and when its Mach number drops to two with respect to the downstream plasma, the heat wave drives a second shock ahead of itself to satisfy mass and momentum conservation in the heat wave reference frame; the heat wave becomes subsonic behind the second shock. For some time both shocks are observed simultaneously. Eventually the initial shock diminishes in strength so much that it can longer be observed, but the second shock continues to propagate long after this time. This sequence of events is a new phenomenon that has not previously been discussed in the literature. Numerical simulation clarifies the origin of the second shock, and its position is consistent with an analytical estimate. © 2006 American Institute of Physics.

Abstract:

We describe measurements characterizing the interaction of ultra-high intensity Petawatt laser pulses with solid targets. Experiments were performed on the Petawatt laser at RAL, and the Titan laser at LLNL. © 2006 Optical Society of America.

Abstract:

Short pulse (< 100 fs) tunable X-ray and VUV laser sources, based on the. free electron laser (FEL) concept, will be a watershed for high energy density research in several areas. These new 4(th) generation light sources will have extremely high fields and short wavelength (similar to 0.1 nm) with peak spectral brightness -photons/(s/mrad(2)/mm(2)/0.1% bandwidth- 10(10) greater than 3(rd) generation light sources. We briefly discuss several applications: the creation of warm dense matter (WDM), probing of near solid density plasmas, and laser-plasma spectroscopy of ions in plasmas. The study of dense plasmas has been severely hampered by the fact that laser-based probes that can directly access the matter in this regime have been unavailable and these new 4(th) generation sources will remove these restrictions. Finally, we present the plans for a user-oriented set of facilities that will incorporate high-energy, intense short-pulse, and x-ray lasers at the first x-ray FEL, the LCLS to be opened at SLAC in 2009.