Patent ID: 8716939

Claim:
A plasma generating apparatus comprising: a gas-ignition chamber for igniting or reigniting plasma; a plasma ignition system for generating a predetermined high frequency signal and a predetermined high voltage; a coaxial cable for transmitting the high frequency signal and the high voltage, the coaxial cable connected between the gas-ignition chamber and the plasma ignition system; the gas-ignition chamber comprising a first connector for connecting the coaxial cable, an applied electrode for applying the high frequency signal and the high voltage thereto, a ground electrode for generating plasma between the applied electrode and thereof, an impedance correction coil for correcting impedance on the high frequency signal and impedance of the applied electrode, the impedance correction coil being disposed between the first connector and the applied electrode, a gas filling chamber for filling an inert gas supplied from a plasma gas supply inlet, and a ceramic tube having a first end and a second end, the applied electrode being disposed outside of the ceramic tube and the ground electrode being disposed inside the ceramic tube, when inert gas is fed into the first end, plasma is generated inside the ceramic tube, and radiating plasma from the second end to a cleaning target; the plasma ignition system comprising a radio-frequency power supply for supplying the high frequency signal to the applied electrode in the gas-ignition chamber, a high-voltage generator for generating the high voltage, a superimposed coil for adding the high voltage to the high frequency signal, a forward wave/reflected wave detector for detecting a forward wave and a reflected wave of the high frequency signal, a matching device for matching impedance on a side of the radio-frequency power supply and impedance on a side of the applied electrode, a second connector for connecting the coaxial cable, and a controller for superimposing the high voltage to the high frequency signal when a ratio of the reflected wave to the forward wave is greater than a predetermined threshold value, and the controller ceasing to superimpose the high voltage when the ratio becomes equal to or smaller than the predetermined threshold value; and the coaxial cable comprising a covering that is grounded through at least one of the first and second connectors.