PURPOSE: To detect the density of a plasma current in a gas without contacting, by irradiating the gas, which is in the plasma state, with a laser light and measuring multiplexed intervals of a prescribed peak of a spectrum which is measured in accordance with the change of a discharge voltage.
CONSTITUTION: A variable wavelength dye laser oscillating device 2 receives a laser light for pump oscillated from a pump laser oscillating device 1 to oscillate the laser light where the wavelength is changed successively in a prescribed range, and the inside of a plasma discharge tube 3 is irradiated with this laser light. The change of the discharge voltage between electrodes D1 and D2 which is caused by this irradiation of the laser light is applied to a lock-in amplifier 5 through a capacitor C together with a signal corresponding to the intensity of the laser light for pump from a photodetector 4, and a spectrum for the wavelength of the laser light is recorded on a chart recorder 6. Multiplexed intervals of the peak are measured on a basis of this recorded data, and a plasma discharge current is detected by a working curve indicating the relation of the plasma discharge current to multiplex intervals of each peak of the spectrum.
MORO NORIO
YAMAGUCHI TADAYOSHI
SAJIKI KAZUAKI
MAEDA SHIROU
HIROSE CHIAKI
