Prof Peter Norreys FInstP;

Abstract:

We have developed PW(0.5ps/500J) laser system to demonstrate fast heating of imploded core plasmas using a hollow cone shell target. Significant enhancement of thermal neutron yield has been realized with PW-laser heating, confirming that the high heating efficiency is maintained as the short-pulse laser power is substantially increased to near equivalent power to the ignition condition. The efficient heating could be caused by the efficient guiding of heating pulse with the hollow cone and self-organized relativistic electron transport. According to the experimental results, we are now developing a 10kJ-PW laser system to study the ignition-equivalent temperature heating physics.

Abstract:

We have developed a PW (0.5 ps/500 J) laser system to demonstrate fast heating of imploded core plasmas using a hollow cone shell target. Significant enhancement of thermal neutron yield has been realized with PW-laser heating, confirming that the high heating efficiency is maintained as the short-pulse laser power is substantially increased to a value nearly equivalent to the ignition condition. It appears that the efficient heating is realized by the guiding of the PW laser pulse energy within the hollow cone and by self-organized relativistic electron transport. Based on the experimental results, we are developing a 10 kJ-PW laser system to study the fast heating physics of high-density plasmas at an ignition-equivalent temperature.

Abstract:

Tens of MeV proton beams have been generated by interactions of the VULCAN petawatt laser with foil targets and used to induce nuclear reactions in zinc and boron samples. The numbers of 11C, 66Ga, 67Ga, 68Ga, 61Cu, 62Zn, 63Zn, and 69mZn nuclei have been measured and used to determine the proton energy spectrum. It is known that (p,n) reactions provide an important method for producing neutron sources and in the present experiment up to ∼109 neutrons sr-1 have been generated via 11B(p,n)11C reactions. Using experimentally determined proton energy spectra, the production of neutrons via (p,n) reactions in various targets has been simulated, to quantify neutron pulse intensities and energy spectra. It has been shown that as high as 4 × 109 neutrons sr-1 per laser pulse can be generated via 7Li(p,n) 7B reactions using the present VULCAN petawatt laser-pulse conditions. © 2004 American Institute of Physics.

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.