John L. Davis

Multi-Kilovolt X-Ray Conversion Efficiencies

X-ray sources in the 3-7 keV energy regime can be produced by laser-irradiating mid- and high-Z gas-filled targets with high-powered lasers. A series of experiments have been performed using underdense targets that are supersonically heated with approximately 35 kJ of 0.35 micrometers laser light. These targets were cylindrical Be enclosures that were filled with 1-2 atms of Xe or Ar gas. L-shell x-ray emission is emitted from the plasma and detected by Bragg crystal spectrometers and x-ray diodes. Absolute flux measurements show conversion efficiencies of approximately 10 percent in the multi-kilovolt x-ray emission. These sources can be used as bright x-ray backlighters or for material testing.

Production of multikilovolt x rays from laser-heated targets

Experiments to develop high photon energy x-ray sources were carried out on the Nova laser. Ten laser beams delivered approximately 39 kJ of energy in 2 ns into a Be cylinder filled with Xe gas. The conversion efficiency into x-rays > 4 keV was measured to be 5 - 15%, which is the highest measured in this photon regime for laser-produced plasmas. The temporal dependence of the x-ray emission indicates that the bulk of the emission is emitted in the first half of the 2 ns pulse. A set of diagnostics were fielded to image the volume in emission as well as provide spectra to measure conversion efficiency.