Professor Justin Wark

Abstract:

We present detailed simulations of the optical spectra emitted from an Argon plasma whose conditions correspond to those thought to prevail within sonoluminescing bubbles. The model incorporates detailed atomic physics based on atomic data from the Opacity Project database, and includes bound-bound, bound-free, and free-free transitions. Line broadening is treated by use of the modified semi-empirical method. The spectral model is used as a postprocessor of hydrodynamic simulations. We find good agreement with experimental spectra and accurately reproduce experimental pulse widths. We also predict that whilst the majority of the optical emission corresponds to bound-free transitions, there remains the possibility of observing line emission in both the UV and IR regions of the spectrum. © 2001 Elsevier Science Ltd. All rights reserved.

Abstract:

The increase in the XUV mass absorption coefficient of liquid aluminium, produced by high-power-laser shock-compression, is measured using XUV laser radiography. At a photon energy of 63 eV a change in the mass absorption coefficient by up to a factor of ∼2.2 is determined at densities close to twice that of solid and electron temperatures of the order of 1 eV. Comparison with hydrodynamic simulations indicate that the absorption coefficient scales with density as ρ1.3±0.2.

Abstract:

We present detailed simulations of the optical spectra emitted from an argon plasma whose conditions correspond to those thought to prevail within sonoluminescing bubbles. The model incorporates detailed atomic physics based on atomic data from the Opacity Project database, and includes bound-bound, bound-free and free-free transitions. Line broadening is treated using the modified semi-empirical method. The spectral model is used as a postprocessor of hydrodynamic simulations. While finding excellent agreement with the shape of experimental spectra, we calculate an intensity that is a factor of 100 greater than that in experiment. We also predict that whilst the majority of the optical emission corresponds to bound-free transitions, there remains the possibility of observing broad line emission in both the UV and IR regions of the spectrum.