Plasma Blow-Off from Electrode Surfaces in the Presence of Vacuum-Ultraviolet Radiation

Experiments have been performed using a low-energy pulser (100 J electrical) to simulate the PITHON wire initiation process by exploding two stainless steel wires and thus providing a UV radiation source. The plasma boundary and density profie near the surface of a sample (electrode material) placed near the radiating wires was observed by taking both a shodowgraph and a hologram. The total energy radiated per wire ranged from 2.0 to 9.5 J/wire for peak currents of 13.5 and 25 kA/wire, respectively. The plasma density profile shows ne = 1.0 × 1018/cm3 near the surface of the sample and ne = 2 × 1016/cm3 near the plasma vacuum interface (plasma front). The final plasma front position has a linear dependence on the total incident energy density with the constant being 1.43 mm/(J/cm2), thus the average expansion velocity dependence on energy density is 1.02 cm/¿s/ -J/cm2. Upon varying the sample material, the sample temperature, magnetic field, and the surface roughness, only the magnetic field and the rough electrode surface reduced the plasma front position by approximately a factor of two.