Progress with the colliding shock lens.

Abstract

The Colliding Shock Lens (CSL) exploits the interference of shock waves in a gas to form a region in which high pressure, temperature and density change the refractive index of the gas, making it possible to focus laser light. They are real optical elements, sometimes have very good optical qualities and can be made out of air. CSL's are dynamic lenses, which last for a few microseconds and are always evolving. As gas structures, they can be applied to focus high power laser light when solid lenses would be damaged. The shocks are generated by spark gaps or exploding wires. In the former case, ignitrons were used to trigger the CSL circuit but are unreliable and have become obsolete. In this thesis an alternative, more reliable and cheaper trigger mechanism is investigated, using needle pins. The CSL's that were tested previously were too small for any practical use and in this thesis a continuation into the feasibility of scaling the optical aperture of the CSL is investigated. Another application of colliding shocks is the formation of virtual capillaries, which are a series of spark gaps set out on the surface of a cylinder, forming a cylin- drical lens. In this thesis a set of exploding wires on a circumference are investigated. The limitations with the above experiments is that physical probes positioned at points of interest would interfere with the experiment, hence making it impractical to determine the parameters of interest as mentioned above. Computational Fluid Dynamics (CFD) is employed in this thesis to try and alleviate the above problem.