Evidence of locally enhanced target heating due to instabilities of counter-streaming fast electron beams

Petra Koester, Nicola Booth, Carlo A. Cecchetti, Hui Chen, Roger G. Evans, Gianluca Gregori, Luca Labate, Tadzio Levato, Bin Li, Mikako Makita, James Mithen, Christopher D. Murphy, Margaret Notle9, Rajeev Pattathil, David Riley, Nigel Woolsey and Leonida A. Gizzi

Phys. Plasmas 22, 020701 (2015)

Abstract

The high-current fast electron beams generated in high-intensity laser-solid interactions require the onset of a balancing return current in order to propagate in the target material. Such a system of counter-streaming electron currents is unstable to a variety of instabilities such as the current-filamentation instability and the two-stream instability. An experimental study aimed at investigating the role of instabilities in a system of symmetrical counter-propagating fast electron beams is presented here for the first time. The fast electron beams are generated by double-sided laser-irradiation of a layered target foil at laser intensities above 10(19) W/cm(2). High-resolution X-ray spectroscopy of the emission from the central Ti layer shows that locally enhanced energy deposition is indeed achieved in the case of counter-propagating fast electron beams.