Spectral and spatial structure of extreme ultraviolet radiation in laser plasma-wall interactions

Intense extreme ultraviolet (XUV) radiation was observed during the interaction of low-temperature laser plasmas and wall materials. Laser plasmas with electron temperature T-e similar to 40 eV were created on massive solid targets (CF2 and Al) by an excimer KrF laser (248 nm/0.5 J/13 ns/1 Hz). The wall was installed in the path of the laser-produced plasma expansion at distances between 0.5 and 3.5 mm. The spectral and spatial structure of XUV radiation (spectral range of lambda similar to 6-20 nm) was studied using a grazing incidence spectrometer with a back-illuminated CCD camera as a detector. XUV spectra of F and Al ions were analyzed. At large plasma-wall distances three-body recombination was identified as the dominant process responsible for ionic level population and radiation. The experiments demonstrate an effective way of creating low-temperature (T-e similar to 1-10 eV) plasmas interacting with solid surfaces (walls).