Publications associated with Plasma Accelerators and Ultrafast X-rays

A study of fast electron energy transport in relativistically intense laser-plasma interactions with large density scalelengths

Physics of Plasmas 19 (2012)

RHH Scott, F Perez, JJ Santos, CP Ridgers, JR Davies, KL Lancaster, SD Baton, P Nicolai, RMGM Trines, AR Bell, S Hulin, M Tzoufras, SJ Rose, PA Norreys

A systematic experimental and computational investigation of the effects of three well characterized density scalelengths on fast electron energy transport in ultra-intense laser-solid interactions has been performed. Experimental evidence is presented which shows that, when the density scalelength is sufficiently large, the fast electron beam entering the solid-density plasma is best described by two distinct populations: those accelerated within the coronal plasma (the fast electron pre-beam) and those accelerated near or at the critical density surface (the fast electron main-beam). The former has considerably lower divergence and higher temperature than that of the main-beam with a half-angle of ∼20°. It contains up to 30% of the total fast electron energy absorbed into the target. The number, kinetic energy, and total energy of the fast electrons in the pre-beam are increased by an increase in density scalelength. With larger density scalelengths, the fast electrons heat a smaller cross sectional area of the target, causing the thinnest targets to reach significantly higher rear surface temperatures. Modelling indicates that the enhanced fast electron pre-beam associated with the large density scalelength interaction generates a magnetic field within the target of sufficient magnitude to partially collimate the subsequent, more divergent, fast electron main-beam. © 2012 American Institute of Physics.

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