Precision X-ray spectroscopy of intense laser-plasma interactions

Polarisation sensitive emission spectroscopy measurements are reported for a petawatt laser-solid target interaction at intensities up to 5 × 1020 W cm−2. These measurements were single-shot and used pairs of highly-orientated graphite spectrometers to resolve the sulphur Ly-α doublet. The sulphur Ly-α1 component shows a large positive polarisation indicative of a low energy electron beam in the plasma, the Ly-α2 component acts as a cross-spectrometer calibration. The measurements show a significant anisotropic or beam-like component to a cold return current.