Prof Peter Norreys FInstP;

Abstract:

The Vulcan laser at the Rutherford Appleton Laboratory in England has been used to show, for the first time, that picosecond laser generated non-thermal K-alpha radiation can be used effectively as a backlighter for radiographic imaging of an implosion. This novel method of x-ray radiography features high temporal resolution, high signal to noise ratio and monochromatic imaging. We present here the Ti K-alpha backlit images of a series of six-beam driven spherical implosions of thin-walled 500 micron Cu doped CD shells. These images, separated by ∼ 0.5ns intervals, capture various states of implosion in and around a stagnation time observed to be ∼ 3.25 ns. Images of imploding coned Cu doped CD shells used in fast ignition research are additionally presented. These images, taken near the previously determined stagnation time, show an imploded core collapsed around an attached gold laser entry cone. These radiographic results were linked to a study of fast electron transport within imploded Cu doped coned CD shells as a result of interaction with a high intensity, short pulse laser. The radiographic results, then, served as a verification of a smooth and uniform implosion and provided an empirical determination of stagnation time, both prerequisites for the electron transport diagnosis.

Abstract:

The Vulcan Nd:glass laser at the Central Laser Facility (CLF) has recently been upgraded to the Petawatt level (10 15 Watts). The facility is now operational to the UK and international user community. During the first user experiments, the power and focussed intensity were increased gradually up to the Petawatt regime. Considerable experience has been gained operating the Vulcan facility in this mode. The Petawatt facility is designed to deliver irradiance on target of 10 21 W.cm -2 for a wide-ranging experimental programme in fundamental physics and advanced applications. This includes the interaction of super-high intensity light with matter, fast ignition fusion research, photon induced nuclear reactions, electron and ion acceleration by light waves and the exploration of the exotic world of plasma physics dominated by relativity.

Abstract:

The Vulcan Nd: glass laser at the Central Laser Facility is a Petawatt (1015 W) interaction facility available to the UK and international user community. The facility came online to users in 2002 and considerable experience has been gained operating the Vulcan facility in this mode. The facility is designed to deliver irradiance on target of 1021 W cm-2 for a wide-ranging experimental programme in fundamental physics and advanced applications. This includes the interaction of super-high-intensity light with matter, fast ignition fusion research, photon induced nuclear reactions, electron and ion acceleration by light waves and the exploration of the exotic world of plasma physics dominated by relativity.

Abstract:

The development of ultra-intense lasers has facilitated new studies in laboratory astrophysics and high-density nuclear science, including laser fusion. Such research relies on the efficient generation of enormous numbers of high-energy charged particles. For example, laser-matter interactions at petawatt (10(15) W) power levels can create pulses of MeV electrons with current densities as large as 10(12) A cm(-2). However, the divergence of these particle beams usually reduces the current density to a few times 10(6) A cm(-2) at distances of the order of centimetres from the source. The invention of devices that can direct such intense, pulsed energetic beams will revolutionize their applications. Here we report high-conductivity devices consisting of transient plasmas that increase the energy density of MeV electrons generated in laser-matter interactions by more than one order of magnitude. A plasma fibre created on a hollow-cone target guides and collimates electrons in a manner akin to the control of light by an optical fibre and collimator. Such plasma devices hold promise for applications using high energy-density particles and should trigger growth in charged particle optics.

Abstract:

The structure of the hot electron beams emitted in laser-solid target interactions was analyzed. It was observed that electron beams were emitted from the rear of thin solid targets irradiated by a high-intensity short-pulse laser. It was shown that the most important condition in which electron beam filamentation due to Weibel-like instabilities become a factor were situations where large regions of low-density plasma exist. The results suggest that Weibel-like instabilities might not be important for the fast-ignitor scheme.