Development of Electromagnetically Pulled-Out Gas Plasma (EPOP) Gun for Medium Vacuum and its Fundamental Discharge Characteristics

Abstract

Electromagnetically pulled-out gas plasma (EPOP) gun was developed, which will be applied to the filtered arc deposition system in order to enhance the nitriding of preparing thin film under medium vacuum. A hot cathode of tungsten (W) filament was employed and DC discharge was generated between the cathode and anode (SUS304). The distance of electrodes was 100 mm. Electromagnetic coils were placed around the cathode, anode and plasma pulled-out duct, separately. Experimental pressure was 0.1 Pa. The following results were obtained. Ignition voltage became lower when the same direction magnetic field was axially applied to the cathode and anode. Minimum voltage for sustaining the discharge became lower when the magnetic filed was applied to the anode. With increasing discharge voltage, the discharge current increased dramatically for the discharge voltage less than 50 V and increased gradually for the voltage more than that. The plasma between the cathode and anode was able to be pulled out to the process chamber by applying magnetic field perpendicular to the discharge axis. The amount of pulled-out plasma increased with increasing the filament current and magnetic flux density for plasma pulling-out.