Hannover 2010 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 14: Miscellaneous

P 14.3: Vortrag

Mittwoch, 10. März 2010, 17:00–17:15, B 302

Divergence optimized targets for laser proton acceleration — •Oliver Deppert¹, Knut Harres¹, Frank Nürnberg¹, Gabriel Schaumann¹, Marius Schollmeier², and Markus Roth¹ — ¹Institut für Kernphysik, Technische Universität Darmstadt, Germany — ²Sandia National Laboratories, Albuquerque, USA

The irradiation of thin metal foils by an ultra-intense, relativistic laser pulse leads to the generation of a highly laminar, high intense proton beam accelerated from the target rear side by the TNSA mechanism. This kind of acceleration mechanism strongly depends on the geometry of the target. The acceleration originates from the formation of a Gaussian-like electron sheath at the rear side of the target leading to an electric field in the order of TV/m. This sheath field-ionizes the target rear side instantaneously and therefore is able to accelerate predominantly protons from a hydrogen contamination layer. The sheath adds an energy dependent divergence to the local beam profile. For further applications it is essential to reduce the divergence already from the "source" of the acceleration process. Therefore numerical simulations where performed with the PIC-Code PSC in order to optimize the proton acceleration with respect to beam divergence. The results leads to the design of three different target geometries. The targets consist of a hemispherical, proton focusing part and a cone-like top part for collimation. Both, the results from the simulations and the technique of fabrication such sub-millimeter to µm targets will be presented. Finally, the results from the experimental campaign at the PHELIX laser system will be compared with the numerical calculations.