K. L. Lancaster[1], D. Farley[1], J. Pasley[1], W. Trickey[1], C. D. Murphy[1], C. Underwood[1], C. Ridgers[1], A. Horne[1], P. Koester[2], R. Gray[3], Z. Davidson[3], J. S. Green[4], A. P. L. Robinson[4], N. Booth[4], R. Heathcote[4], M. Notley[4], R. Clarke[4], I. Musgrave[4], C. Spindloe[4][5].

[1] York Plasma Institute, Department of Physics, University of York, Heslington, York, YO10 5DD, UK.

[2] Intense Laser Irradiation Laboratory (ILIL), Instituto Nazionale di Ottica (INO-CNR), Via Moruzzi I, 56124, Pisa, Italy.

[3] SUPA Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.

[4] Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK.

[5] Scitech Precision Ltd, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK.

Currently we are able produce with laser plasma interactions some of the most extreme conditions on earth. When ultra-intense lasers are focused on to solid material, the fields associated with the laser are so strong that electrons can easily escape the atoms in the material. Absorption of the laser pulse results in the generation of a population of relativistic electrons, with currents on the order of Mega Amps. The physics associated with how the electrons are produced and subsequently transported in plasma is complex and proves challenging to diagnose and study. Importantly, these fast electrons are the driver for much of the subsequent physics during these interactions including generation of energetic particles/ photon sources, unique atomic physics states such as hollow atoms, hydrodynamic phenomena, production of warm / hot dense matter relevant to stellar interiors, heating of matter relevant to alternative laser driven fusion schemes such as fast ignition, and conditions relevant for understanding of nuclear astrophysics in the most extreme objects in our universe.

This talk will illustrate some of the experiments happening on petawatt-class lasers concerning how to control important fast electron beam parameters (such as divergence) using novel structured targets. Alex Robinson et al[1] first proposed using targets incorporating a resistivity gradient to confine fast electrons. At the material interface of a high resistivity feature, e.g. a wire, surrounded by a lower resistivity material a strong magnetic field is generated which confines electrons to areas of higher resistivity and higher current density. In this talk experiments using targets with novel silicon embedded features created by Scitech Precision Ltd* using MEMS technology will be presented. A novel duel channel front surface imaging system was created in order to enable both pre-shot alignment and on-shot focal spot position, information critical for performing these types of complex experiments. Data from a recent guiding experiment using the VULCAN PW system will be presented. Temperatures at the rear side of guiding targets have been inferred from rear surface expansion velocities (measured using optical probing techniques) in conjunction with radiation-hydrodynamic simulations.

[1] A. P. L. Robinson and M. Sherlock, PoP, 14 083105 (2007)

* http://scitechprecision.com/