PLEIADES: A picosecond Compton scattering x-ray source for advanced backlighting and time-resolved material studies

The PLEIADES (Picosecond Laser-Electron Inter-Action for the Dynamical Evaluation of Structures) facility has produced first light at 70 keV. This milestone offers a new opportunity to develop laser-driven, compact, tunable x-ray sources for critical applications such as diagnostics for the National Ignition Facility and time-resolved material studies. The electron beam was focused to 50 mum rms, at 57 MeV, with 260 pC of charge, a relative energy spread of 0.2%, and a normalized emittance of 5 mm mrad horizontally and 13 mm mrad vertically. The scattered 820 nm laser pulse had an energy of 180 mJ and a duration of 54 fs. Initial x rays were captured with a cooled charge-coupled device using a cesium iodide scintillator; the peak photon energy was approximately 78 keV, with a total x-ray flux of 1.3x10(6) photons/shot, and the observed angular distribution found to agree very well with three-dimensional codes. Simple K-edge radiography of a tantalum foil showed good agreement with the theoretical divergence-angle dependence of the x-ray energy. Optimization of the x-ray dose is currently under way, with the goal of reaching 10(8) photons/shot and a peak brightness approaching 10(20) photons/mm(2)/mrad(2)/s/0.1% bandwidth. (C) 2004 American Institute of Physics.