Imaging and spectroscopy of laser-produced colliding plasmas

Laser-produced plasmas are formed when short pulse, high power lasers are focused onto a surface Applications range from VUV / X-ray sources for lithography, microscopy and radiography to X-ray lasers, thin him deposition, analytical spectroscopy and electron / ion beam generation A battery of particle and optical techniques are currently being used to fully characterise the properties of laserproduced plasmas.\ud \ud Over the past forty years much experimental and theoretical / computational work has focussed on the generation and expansion of LPP’s in vacuum Recently however, the dynamics of LPP’s expanding into background gasses has received increased interest This has been driven by the need to control the growth conditions of thin films produced using pulsed laser deposition The dynamics of LPP’s expanding into background gasses are very different from that of the vacuum case and leads to plume splitting and sharpening effects.\ud \ud Although much is known about the properties of laser-produced plasmas expanding in vacuum and into background gasses, very little is known about the expansion and interaction of a LPP into another LPP The aim of this project is the study of this system, colliding laser-produced plasmas Colliding plasma experiments may be cast as a model system for atmospheric and/or astrophysical colliding systems, for example when tracer elements are injected into supersonic winds at high altitude or collisionless plasma interaction in young supernova remnants Colliding plasmas have also been considered as a possible solution to the problem of particulate deposition in PLD.\ud \ud In order to study colliding plasmas m this work we have used, primarily, three diagnostic techniques VUV photoabsorption imaging was used in order to track the evolution of dark plume matter, or non-emitting plasma species residing m ground and metastable states We have also performed combined conventional gated CCD imaging and imaging spectroscopy to study excited species in the interaction region