Oxford Centre for High Energy Density Science (OxCHEDS)

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:

The optical reflectance of a strong shock front in water, which increases with pressure above 100 GPa, was discussed. The water Hugoniot equation of state up to 790 GPa was also determined. The shock velocity measurements, made by detecting the Doppler shift of reflected light, were used for the purpose. It was found from a fit to the reflectance data, that an electronic mobility gap ∼2.5 eV controls thermal activation of electronic carriers at pressures in the range of 100-150 GPa. The results show that above 150 GPa, electronic conduction contributes significantly to the total conductivity along the Neptune isentrope.

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.