DIAGNOSTICS OF HIGH PRESSURE MICROWAVE DISCHARGE PLASMA BY LANGMUIR PROBE

摘要

Probe characteristics measured in high pressure microwave excited helium and argon plasmas are characterized using simple algebraic functions. A microwave power from 100-400 W is used to generate helium and argon plasmas. Evolutions of electron concentration and temperature with increasing microwave power have been studied. It is found that electron concentration increases linearly with increasing microwave power both for 400 and 500 torr. The rate of production of ions in helium discharge is higher than that of argon because of higher direct electron impact ionization rate coefficient of helium. Electron temperature decreases with increasing microwave power because electron concentration increases with increasing power and consequently electron temperature decreases due to the screening of microwaves inside the plasma column.