Refluxing of fast electrons in solid targets irradiated by intense, picosecond laser pulses

Quinn, M. N. and Yuan, X. H. and Lin, X. X. and Carroll, D. C. and Tresca, O. and Gray, R. J. and Coury, M. and Li, C. and Li, Y. T. and Brenner, C. M. and Robinson, A. P. L. and Neely, D. and Zielbauer, B. and Aurand, B. and Fils, J. and Kuehl, T. and McKenna, P. (2011) Refluxing of fast electrons in solid targets irradiated by intense, picosecond laser pulses. Plasma Physics and Controlled Fusion, 53 (2). ISSN 0741-3335 (https://doi.org/10.1088/0741-3335/53/2/025007)

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Abstract

The propagation of fast electrons produced in the interaction of relativistically intense, picosecond laser pulses with solid targets is experimentally investigated using K-alpha emission as a diagnostic. The role of fast electron refluxing within the target, which occurs when the electrons are reflected by the sheath potentials formed at the front and rear surfaces, is elucidated. The targets consist of a Cu fluorescence layer of fixed thickness at the front surface backed with a propagation layer of CH, the thickness of which is varied to control the number of times the refluxing fast electron population transits the Cu fluorescence layer. Enhancements in the K-alpha yield and source size are measured as the thickness of the CH layer is decreased. Comparison with analytical and numerical modelling confirms that significant refluxing occurs and highlights the importance of considering this phenomenon when deriving information on fast electron transport from laser-solid interaction experiments involving relatively thin targets.