CONVERSION OF LASER-LIGHT INTO SOFT X-RAYS WITH 3-NS AND 30-PS LASER-PULSES

The X-ray emission from planar targets made of aluminum, copper, or gold irradiated by a frequency-doubled Nd laser (530-nm wavelength and 10(12)-10(14)-W/cm2 laser intensity) was measured at two pulse durations: 3 ns and 30 ps. We absolutely measured the X-ray emission with spectral, temporal, and spatial resolution in the wavelength range 3 angstrom < lambda < 250 angstrom by using filtered bolometers, a transmission grating spectrometer, X-ray diodes, and an X-ray streak camera as diagnostics. In addition, the absorption of laser light was measured. For the short, 30-ps laser pulse the conversion of incident laser energy into X rays was considerably less than that with the long, 3-ns pulse. This is caused by less absorption of laser light and, in addition, by less conversion of absorbed laser energy into X rays in the case of the short pulse. The results are compared with numerical simulations performed with the MULTI hydrocode.