Generation of a Large Diameter He Cascade Arc Plasma for a Plasma Window Application

We fabricated a cascade arc discharge source with a channel diameter of 8 mm for various applications to virtual vacuum interface (plasma window). Stationary helium arc plasma up to a discharge current of 100 A was generated, and the performance as plasma window was investigated. The pressure ratio of high-pressure discharge section to low-pressure vacuum side was above 70 at a 50-A He discharge with a gas flow rate of 0.2 L/min. To characterize the plasma at the anode electrode, emissions of vacuum UV and visible wavelengths were observed. Spectral analysis of He I continuum spectra and H-β Stark broadening showed that the plasma temperature was around 0.9 eV and density was 3.4×10
¹³
cm
^-3
for a 100-A He discharge with a gas flow rate of 0.05 L/min.