Prof Peter Norreys FInstP;

Abstract:

Positron emission tomography (PET) is a powerful diagnostic/imaging technique requiring the production of the short-lived positron emitting isotopes 11C, 13N, 15O and 18F by proton irradiation of natural/enriched targets using cyclotrons. The development of PET has been hampered due to the size and shielding requirements of nuclear installations. Recent results show that when an intense laser beam interacts with solid targets, megaelectronvolt (MeV) protons capable of producing PET isotopes are generated. This report describes how to generate intense PET sources of 11C and 18F using a petawatt laser beam. The work describing the laser production of 18F through a (p,n) 18O reaction, and the subsequent synthesis of 2-[18F] is reported for the first time. The potential for developing compact laser technology for this purpose is discussed.

Abstract:

Measurements of ultrahigh magnetic fields produced during intense laser interaction with solids were presented. Polarization measurements of high-order laser harmonics suggest the existence of magnetic field strengths of 0.7±0.1 GG. It was found that denser regions of the plasma can be probed using higher order harmonics. The technique was found to be useful for the measurements of multi-GG level magnetic fields.

Abstract:

The VULCAN laser was used for investigating 7Li(p,n) 7Be reactions with the help of Cu and CH primary and LiF secondary targets. CR-39 plastic track detector measured the neutron yield which was 3×10 19 Wcm -2 for CH primary targets and up to 2×10 8 sr -1 for Cu primary targets. At various angles, the angular distribution of neutrons was measured that indicated a relatively anisotropic distribution of neutrons over 180°. The reactions were found to be fficient for neutron radiography on high repetition, table-top lasers.

Abstract:

The energy transport properties were investigated within a dense plasma using a Kα fluorescence layer. A spherically bent Bragg crystal monochromatic two-dimensional (2D) x-ray imaging technique was utilized to record the origin of Kα photons created in a 20 μm thick buried Ti or Cu fluor layer in a planar Al or CH target. It was found that one or more processes cause lower energy electrons to travel at very large angles very near the front surface of the target. The results show that laser generated electrons penetrating through more than 100 μm of Al, emerge from a >150 μm wide region and travel in a 40° full-width cone.

Abstract:

The ultrafast heating of implosions using cone/shell geometeries was discussed. The study was carried out by using the 1054 nm, nanosecond, 0.9 kJ output of the VULCAN Nd:glass laser to drive 186 μm diameter, 6 μm wall thickness Cu-dopped deuterated plastic (CD) shells in 6-beam cubic symmetry. It was found that x-ray preheat, combined with lower ablation pressures, indicate that infrared drive was unlikely to be useful in full scale direct drive ignition design. The results show that the higher density of the compressed plasma promotes more collimated flow, but at the cost of reduced background heating.