Probe diagnostics of high-pressure microwave plasmas for shock wave propagation study

High pressure (∼1 Torr) microwave plasmas in argon are investigated in the range of gas pressures from 400–1000 mTorr for microwave (MW) power levels of 1300–1600 W by means of electrical probes. Electron number density, electron temperature, and plasma potential obtained from single Langmuir probe (SP), floating double probe (DP), and emissive probe (EP) are compared with one another. Standard analyses for the single and double probe characteristics are performed, whereas the inflection point method is used for determining the plasma potential from the emissive probe. Averaged over all power levels, the range of values for the plasma parameters are determined to be (i) 3.5–4.9 eV from the SP and 2.0–2.4 eV from the DP method for electron temperatures, (ii) 0.92–3.5 × 10¹¹ cm⁻³ from the SP and 1.2–2.7 × 1011 cm⁻³ from the DP method for electron densities, and (iii) 17.5–22.6 V from the SP and 12.4–36.6 V from the EP method for the plasma potentials.