Measurements of plasma parameters in low-frequency (60 Hz) hydrogen discharge

Measurements of low-frequency (LF) hydrogen plasma were done with a single Langmuir probe and an optical emission spectroscopic method. The electrodes has a 10 cm diameter with a 5 cm gap. Hydrogen plasma was generated using LF, DC, and RF power. LF-hydrogen plasma wasn't a continuous discharge, but a series of short-lived discharge. The breakdown voltage had a minimum value at 400 mTorr. The electron temperature was about 1.5 eV, the electron density was ∼109 cm-3, and the current density was about 76 μA/cm2. Comparison with other powers (DC and RF), the parameters of the LF-plasma had similar values. The spectrum of the LF-plasma was similar to the DC-plasma and showed different characteristics from the RF-plasma. For the LF plasma, hydrogen Balmer lines are stronger and H2 molecule bands are weaker than the RF plasma