X-ray emission caused by Raman scattering in long-scale-length plasmas

By analysis of data from a specific set of laser-plasma interaction experiments, it is argued that stimulated Raman scattering (SRS) is responsible for the hard (>30-keV) x rays emitted from the targets. The Novette laser [K. R. Manes et al., Laser Part. Beams 3, 173 (1985)] was used to irradiate thick, gold targets with up to 4 kJ of 0.53-μm light in 1-ns, Gaussian pulses at average intensities of (1–200)×${10}^{14}$ W/${\mathrm{cm}}^2$, producing approximately planar plasmas with temperatures of order 3 keV and density-gradient scale lengths of order 250 μm. The spectrum, amplitude, and timing of the hard x rays emitted by the plasma were measured along with various properties of the scattered light. All the data are consistent with the hypothesis that SRS is the source of the hot electrons that emit the x rays, and some data conflict with any other plausible hypothesis.