Spectroscopy of the tungsten plasma produced by pulsed plasma-ion streams or laser beams

The paper reports on experiments, which concerned studies of plasma produced from a tungsten (W) target bombarded by powerful (ca. 5 μs, 1–5 MW/cm2) plasma-ion streams in RPI-IBIS plasma accelerator, and a similar target irradiated with intense Nd:YAG laser pulses (0.5 J, 3 ns, ca. 5.3 × 109 W/cm2) in another vacuum chamber. In both experiments optical measurements were performed with a Mechelle®900 spectrometer, which enabled the spectrum from 300 nm to 1100 nm to be recorded, and different WI- and WII-lines to be identified. From space- and time-resolved measurements of those lines, basic W-plasma parameters were estimated. During W-plasma expansion the electron temperature was found to be 0.8–1 eV and electron concentration (2–8) × 1016 cm−3. The emission of higher-ionized W-ions (up to W+6) was confirmed by measurements with an ion-energy analyzer. Structural changes in the irradiated targets were investigated with an optical microscope and SEM.