Oxford Centre for High Energy Density Science (OxCHEDS)

Abstract:

A range of laser-driven proton-induced reactions in copper from a petawatt laser-solid interaction were investigated. The experiment was carried out on petawatt arm of VULCAN Nd:Glass laser at the Rutherford Appleton Laboratory, U.K. where Cu foils were exposed to the proton beams from the laser-irradiated target which induced nuclear reactions. This technique used a very thin layer of copper which was inserted into the proton beam which had a smaller impact on the proton beam and was optimized according to the energies and intensities of the protons. The results show that the energy spectrum of the accelerated protons was in the range of 10-40 MeV.

Abstract:

Calculations of the modal photon densities and gain in a photopumped Cl XVII-Se XXXII X-ray laser are presented. In this paper we undertake a realistic simulation of the generation of both Cl and Se plasmas, using a high-power optical laser, which includes radiation from both Ly-α fine-structure components of H-like Cl pumping the 2p3/2-5d5/2 transition in Li-like Se. The calculations are performed in two dimensions in a realistic geometry taking into account plasma gradients. This gives information about the spatial extent and time evolution of X-ray lasing gain on the 5-4 transitions (39.5 Å) in Li-like Se. We find that gain (about 200 cm^-1) is expected only when the optical laser includes a pre-pulse. Calculations show that the absorption of pumping radiation in the pumped plasma can reduce the gain by 20%. Time-dependent calculations have shown that the gain is reduced by 30% in comparison to the steady-state calculations. The effect of the spectral profile and self-radiation of 5d5/2-2p3/2 transition in Li-like Se reduces the gain by about 2%. © 2003 Elsevier Ltd. All rights reserved.

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.