Characteristics of high energy Kα and Bremsstrahlung sources generated by short pulse petawatt lasers

We have measured the characteristics of high energy Kalpha sources created with the Vulcan Petawatt laser at RAL and the JanUSP laser at Lawrence Livermore National Laboratory. High energy x-ray backlighters will be essential for radiographing high energy-density experimental science targets for NIF projects especially to probe implosions and high areal density planar samples. Hard Kalpha x-ray photons are created through relativistic electron plasma interactions in the target material after irradiated by short pulse high intensity lasers. For our Vulcan experiment, we employed a CsI scintillator charge coupled device (CCD) camera for imaging and a CCD camera for single photon counting. We have directly measured the 22 keV Ag Kalpha source size using the RAL petawatt laser and performed knife-edge measurements of a 40 keV Sm Kalpha source using the JanUSP laser. The measured source sizes are both similar to60 mum full width half maximum. We have also measured the Ag Kalpha conversion efficiencies. At laser intensities of 1x10(18) W/cm(2) range, the conversion efficiency at 22 keV is similar to1x10(-4). (C) 2004 American Institute of Physics.