Professor Simon Hooker

Abstract:

The inverse bremsstrahlung (IB) heating rates of a plasma as a function of density and laser intensity were calculated using a molecular dynamic (MD) code. The code belonged to the class of particle-particle-particle-mesh codes. The equations solved by the MD code avoided several assumptions which were inherent to alternative methods. The results of the MD code were compared to previous results for plasmas of low coupling. The results of the calculations for dense, moderately coupled plasmas were also presented. An analytic expression for the IB heating rate, based on a fit to the rates calculated by MD code, was also presented.

Abstract:

A molecular dynamic (MD) code is used to calculate the inverse bremsstrahlung (IB) heating rates of a plasma as a function of density and laser intensity. The code belongs to the class of particle-particle-particle-mesh codes. Since the equations solved by the MD code are fundamental, this approach avoids several assumptions which are inherent to alternative methods, for example those which employ a Coulomb logarithm, and is not restricted to weakly coupled plasmas. The results of the MD code are compared to previously published results for plasmas of low coupling. The results of calculations for dense, moderately coupled plasmas are also presented. An analytic expression for the IB heating rate, based on a fit to the rates calculated by the MD code, is suggested. This expression includes terms nonlinear in the plasma density.

Abstract:

The results of the first experimental demonstration of a short-wavelength laser driven within a gas-filled capillary-discharge waveguide were described. The xenon gas was mixed with the hydrogen and strong lasing on the 4d 95d-4d95p transition in Xe8+ at 41.8 nm was observed. Analysis shows that lasing was strongly correlated with good guiding of the pump pulse and numerical simulations indicate that gain is likely to have been achieved over a significant fraction of the 30 mm length of the capillary. The success of this proof-of-principle experiment suggests that this and other short-wavelength lasers could be driven within waveguides of this type, leading to increased energy output and reduced beam divergence.

Abstract:

We present the status of optical field ionization soft X-ray lasers. The amplifying medium is generated by focusing a high-energy circularly polarized 30-fs 10-Hz Ti: sapphire laser system in a gaseous medium. Using xenon or krypton, strong laser emission at 41.8 and 32.8 nm, respectively, has been observed. After presenting the basis of the physics, we present recent characterization of the sources as well as dramatic improvement of their performances using the waveguiding technique.

Abstract:

In many cases the length over which particles can be accelerated in a laser-driven plasma accelerator is limited by refraction or diffraction of the driving laser pulse. In order to overcome this limitation the driving pulse must be guided or channeled through the plasma, In this paper we briefly review of the techniques used to guide laser pulses with peak intensities up to 10(19) W cm(-2), and describe recent experimental results.