Patent ID: 8214173

Claim:
A method of measuring electron temperature of generated plasma, comprising the steps of: providing at least helium gas to a predetermined container to generate plasma in the predetermined container; irradiating laser light, by using a laser irradiation device, to the generated plasma, the laser light having wavelength which is capable of exciting atoms of the helium gas in a metastable state, to excite the atoms in the metastable state; obtaining absorption amount information, by using a laser irradiation device, representing an amount of the laser light absorbed by the atoms in the metastable state; computing density of the atoms of the helium gas in the metastable state in an irradiation area of the laser light in the plasma based on the absorption amount information by using a computer; measuring each of light emissions, by using a camera, due to level transition processes from two different excited states of the helium gas in the plasma to a state having an energy level lower than an energy level of the excited states and computing an emission intensity ratio between the light emissions; and computing electron temperature of the generated plasma based on the emission intensity ratio and the computed density of the atoms of the helium gas in the metastable state by using the computer.