Experiments on conversion of the PHELIX laser light into soft X-rays using a hohlraum scheme

In experiments on the conversion of the PHELIX laser light into soft X-rays, the Petawatt High-Energy Laser system for Ion beam eXperiments – “Phelix” (Nd:glass, =1054 nm) was used at the basic frequency. The chirped laser pulse of 1.4 ns duration and energies up to 270 J was focused onto the target by a lens with 4 m focal length. The diameter of the focal spot on the wall of the primer hohlraum measured by means of a pin-hole camera in Xrays with h >1.5 keV was of ~200-300 μm, resulting in the laser intensities up to 2 10 W/cm. The laser irradiates the wall of the gold cylinder at the 45 through the open entrance hole (see fig.1). Diagnostic tools were placed around the target inside the spherical chamber with diameter of 110 cm evacuated up to 10 mbar [1] The plasma diagnostics experimental setup includes different types of techniques providing spectral, spatial and temporal resolution of X-ray radiation [2]. Two pinhole cameras were used to image the hohlraum plasma in X-rays. By means of the pin-hole placed on the front target side and covered with a 5 m thick Ti-filter one could view the radiation occurring in the laser focal spot; the pin-hole placed at the rear target side was equipped with a glance incidence glass mirror and thin 0.9μm CH-filter, allowing the hohlraum plasma imaging at the photon energies of 0.2-0.28 keV. Absolutely calibrated vacuum Xray diodes (XRD) with carbon cathodes covered by 0.9 m thick CH-filters were used for time resolved measurements of the X-ray flux transmitted through the 0.1 m Au-foil in the range of 0.1-1 keV. Two symmetrically placed transmission grating spectrometers (TGS) measured the spectra distribution of the hohlraum radiation from the rear target side.