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Project A.2.5

Ultra-thin carbon foils for radiation pressure ion acceleration and soliddensity Thomson source

Over the past few years, targets of few nanometer thickness performed exceptionally well for efficiently accelerating ion bunches by the radiation pressure of high power laser pulses. Diamond-like carbon (DLC) has outstanding properties 6; most importantly due to its low absorption it can withstand spurious pre-pulses, enabling relativistic laser interaction with targets as thin as the laser skin depth. For applications in A.3.1 and A.3.5 as well as for the depending projects it is of vital importance to develop the DLC-production to a routine status that allows mass production for few-Hz repetition rate experiments.

This involves developing methods to quantify relevant parameters such as thickness and density during the production process with an accuracy of several percent. Furthermore, diagnostics of the free-standing targets will be developed to bridge the gap between the production process and the actual experiment. Supported by numerical simulations advanced target geometries are envisioned, employing nano-tube technologies for density tailoring, focused ion beam processing and master stamps to generate almost arbitrary shaped targets, ranging from hemispherical shells to micrometer-size guiding structures.

Especially the latter promises a way to concentrate laser energy to spot sizes below the current limit of a few micrometers. Thus, focused intensities could be increased by a factor of 10 using advanced targetry. External collaborators are Prof. M. Roth (TU Darmstadt) and Dr. C. Spindloe (RAL).