Debris and VUV emission from a laser-produced plasma operated at 150 Hz using a krypton fluoride laser

The output of a KrP laser (248 nm) operating at 150 Hz was focused onto metal targets to produce plasmas which emitted strongly in the VUV and XUV regions. Quantitative measurements of target debris produced in a laser-plasma light source show (1) that low pressures (~ 100 mTorr) of He buffer gas reduce the debris collected 150 mm from the target by more than an order of magnitude and (2) that the amount of debris collected rises faster than linearly with laser pulse energy in the 100-300-mJ range. This observed suppression of debris is explained in terms of a counterstreaming plasma mechanism. High-resolution absorption spectra observed in the 50-100-nm range using the laser-plasma light source showed (1) that VUV continua produced using the KrF laser or a NdrYAG laser (1064 nm) as a driver are equally line-free and (2) that exposure times using S WR plates were an order of magnitude shorter for the KrF driver operating at 150 Hz and 300 mJ/pulse than for the Nd:YAG driver operating at 10 Hz and 600 mJ/pulse.