Laué diffraction hard x-ray spectrometer for laser fusion diagnostics

We show that a crystal spectrometer used in the Laué mode is a useful diagnostic of high-energy x-ray emission from laser fusion plasmas. It has good collection efficiency and adequate energy resolution for continuum measurements. The instrument measures time integrated x-ray spectra with a resolving power E/ΔE≊10 for photon energies between 60 and 300 keV. A strong signal and no detectable background are obtained in laser fusion experiments where ∼15 J of x rays are released in a pulsed (1 ns), hard (kT≊200 keV) spectrum. A Lanex/Tri-X phosphor/film combination is used as a focal plane detector; we report its relative energy calibration. Because of the imperfection of available crystals, detailed measurements of reflectivity along the crystal are required to achieve absolute calibration.