Prof Peter Norreys FInstP;

Abstract:

In a recent experiment at Lawrence Berkeley National Laboratory (Geddes et al 2008 Phys. Rev. Lett. 100 215004), electron bunches with about 1 MeV mean energy and small absolute energy spread (about 0.3 MeV) were produced by plasma wave breaking on a downward density ramp. It was then speculated that such a bunch might be accelerated further in a plasma of low constant density, while mostly preserving its small absolute energy spread. This would then lead to a bunch with a high mean energy and very low relative energy spread. In this paper, trapping of a low-energy, low-spread electron bunch on a downward density ramp, followed by acceleration in a constant-density plasma, has been explored through particle-in-cell simulations. It has been found that the scheme works best when it is used as a separate injection stage for a laserwakefield accelerator, where the injection and acceleration stages are separated by a vacuum gap. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Abstract:

Fusion power is a step closer with the demonstration of control over the extreme thermal radiation pressure created by high-power laser beams within a cavity.

Abstract:

Laser-plasma wakefield-based electron accelerators are expected to deliver ultrashort electron bunches with unprecedented peak currents. However, their actual pulse duration has never been directly measured in a single-shot experiment. We present measurements of the ultrashort duration of such electron bunches by means of THz time-domain interferometry. With data obtained using a 0.5 J, 45 fs, 800 nm laser and a ZnTe-based electro-optical setup, we demonstrate the duration of laser-accelerated, quasimonoenergetic electron bunches [best fit of 32 fs (FWHM) with a 90% upper confidence level of 38 fs] to be shorter than the drive laser pulse, but similar to the plasma period. © 2010 The American Physical Society.

Abstract:

WP10 is one of the working packages of the HiPER project and it has the goal of addressing, in a systematic and programmatic way, some of the key experimental uncertainties on the way towards fast ignition (and shock ignition) in a perspective of risk reduction, so to contribute to the definition of the basic characteristics of the HiPER project. The paper describes the key points contained in the short term HiPER experimental road map, as well as the results of two first experiments performed in "HiPER dedicated time slots" in European Laser Facilities. © 2010 American Institute of Physics.