J. Edwards

Measurement and Analysis of Radiation Transport in Laser-Irradiated Targets

The transport of soft-X-ray radiation through thin foil plastic targets, 0.1 and 5 μm thick, has been studied using time-resolved XUV spectroscopy in the 10 to 70 A spectral wavelength region. An intense source of radiation was produced by overcoating one side of the target with 0.1 μm of gold and irradiating it with green laser light at an intensity between 1·1014 and 5·1014 W cm-2. The experimental results were simulated with a multi-group radiation transport calculation which was coupled to a one-dimensional hydrodynamics model.

Time resolved soft x‐ray imaging with submicron spatial resolution (invited)

Recent progress in multilayered mirror technology has allowed the developments of novel imaging systems for probing of high density plasmas in the soft x‐ray regime. The experimental system described here basically consists of a spherical multilayered mirror which reflects a narrow band (∓5 eV) of soft x‐ray radiation in the 50 to 200 eV energy region. The mirror images either the self‐emission of a laser produced plasma and/or the shadow of the expanding plasma generated by a separate laser produced x‐ray source with approximately 50× magnification in the image plane and submicron resolution in the target plane. The time resolution of about 150 ps is obtained with either a gated microchannel plate intensifier as detector or a short pulse x‐ray backlighter. This imaging technique has been applied to several different studies of laser produced plasmas. Measurements of the overdense plasma profiles were carried out by imaging the self‐emission produced by bremsstrahlung. Two‐dimensional x‐ray radiographs of...

High density plasmas for recombination X-ray lasers

The scaling of recombination XUV lasers to shorter wavelengths requires laser plasmas produced at initial electron densities close to solid. With pump laser pulses longer than a few tens of picoseconds the hydrodynamic motion of the plasma during the interaction makes this difficult to achieve. In contrast, when picosecond laser pulses are used the laser energy is absorbed close to solid density since the plasma expansion is insignificant during the laser pulse. This results in hot near solid density plasmas which are needed for hydrogenic recombination X-ray lasers operating in the water window. Experimental observations have shown that a fully ionized aluminium plasma with a temperature of about 400 eV and a density well above 1023 cm−3 is produced when an aluminium target is irradiated with a single 3.5 ps high power KrF laser pulse.

Experimental observations of L‐ and M‐shell spectra emitted from plasmas produced by the irradiation of solid targets with single 3.5 ps, KrF laser pulses

L‐ and M‐shell x‐ray spectra obtained when solid targets were irradiated by single, 3.5 ps, KrF laser pulses with irradiances above 1016 W cm−2 are presented. Modeling of the experimental conditions with a one‐dimensional hydrocode and time‐dependent atomic physics is shown to be consistent with the experimental results.

Laser Plasma Interaction Studies Relevant for Inertial Confinement Fusion

Several basic processes occurring during the interaction of laser irradiation with matter have been investigated by using the high power laser systems of the SERC Central Laser Facility. The main effort of the recent research concentrated on ICF related studies with improved laser illumination uniformity generated by Random Phase Plate (RPP) Arrays and Induced Spatial Incoherence (ISI) techniques or a combination of both. In addition, highly transient plasmas have been produced by a prepulse-free 12 ps high power Raman shifted KrF laser pulse.