Prof Peter Norreys FInstP;

Abstract:

Petawatt (PW) lasers are unique tools to study plasmas under extreme conditions. There are many applications for these plasmas that potentially have an impact on a wide range of scientific disciplines. A number of these are highlighted here in this review including: fast ignition of fusion targets; high brightness x-ray harmonic generation from oscillating plasma surfaces and the production of super-strong magnetic fields. This is a rich field of investigation, and space prevents a detailed discussion of some of these fascinating topics, including electron and ion acceleration processes that were highlighted at the London conference. Fortunately, they are presented elsewhere in other invited papers in this special issue.

Abstract:

Recent progress in the physics of fast ignition of fusion targets is reviewed here. Fundamental studies on hot electron energy transport show that the scheme looks promising if the heating pulse can be guided close enough to a compressed core. The idea of using cone-guided compression was first demonstrated experimentally under a Japan-UK collaboration. The use of the gold cone was extremely successful and showed a 103 neutron increase out of CD target implosion with a 300 J/0.5 ps enforced heating laser pulse. The heated temperature was close to 1 keV. In order to increase the temperature to 10keV, a 10kJPW-1 laser system is necessary. Osaka University has started constructing such a laser system.

Abstract:

Vulcan is established as a world leading user facility for studies of ultra-high intensity laser interactions with matter. The Petawatt(PW) Upgrade project will deliver an order of magnitude increase in laser power to target, delivering interaction intensities of 10 21 Wcm -2. Before commencing operation to users a commissioning study was carried out. The objectives of this investigation were: To perform radiological surveys of the facility in anticipated target configurations and to install additional shielding for high-Z interactions as required To measure the target irradiance and the X-ray spot size To investigate the effects of electromagnetic noise on the chamber and target area equipment To determine the level of debris produced from the target and to devise a suitable operating scheme to protect chamber optics from damage Installation of an optical probe Contrast measurement of the laser pulses This report will review the experimental and radiological data obtained from the thirteen solid target interaction shots fired during the commissioning run in the newly constructed PW interaction facility 1) where doses of 45 mSv @ 1m were obtained. Commissioning of the PW laser and compressor chain is reported in separate articles, as is the commissioning of the large aperture gratings at high laser fluences 2).

Abstract:

The transport of intense relativistic electron beams in solid density plasma was analyzed. Ponderomotive kinetics modeling code (MPK) for the average relativistic laser-plasma interaction for laser absorption in under-dense or below critical density plasma was proposed. The focused peak intensity of the Petawatt laser system was measured as high as 3.1020W / cm 2. It was found that there was significant lateral electron transport, but of low energy electrons, into the solid.

Abstract:

Experimental measurements of electron transport and isochoric heating in 100 J, 1 ps laser irradiation of solid Al targets are presented. Modeling with a hybrid PIC code is compared with the data and good agreement is obtained using a heuristic model for the electron injection. The relevance for fast ignition is discussed.