To ignite arc plasma of operating gas such as argon gas, nitrogen whose discharge starting voltage is high and air only by a high frequency induction coil without using a special igniter.
Helium gas 8 is introduced in the first place under pressure close to atmospheric pressure to an electric insulating tube 1 around which a high frequency induction coil 2 is wound, and an electric current is flowed to the high frequency induction coil 2 from a high frequency power source 3, and glow discharge of the helium gas is generated. Next, argon gas 9 is added to the helium gas 8, and after discharge of its mixed gas is generated, the introduction of the helium gas 8 is stopped, and it is transferred to arc plasma of the argon gas 9. In a condition where arc plasma of the argon gas is generated, operating gas such as nitrogen and air 10 is added, and the gas mixing ratio is changed so that its gas concentration is gradually increased, and the introduction of the argon gas 9 is finally stopped, and it is transferred to arc plasma of the operating gas.
SAKAKIBARA YASUSHI
KOGUCHI MAKOTO
