Title : "Development of Metal Vapour Vacuum Arc (Mewa) Ion Source in Thailand"

Researcher : Banchob Yotsombat, Thiraphat Vilaithong, P. Pramukkul, S. Sansongsiri, S. Davydov, V. Ano and R. Rungroenukel

Office of Researcher : PHYSICS


MEVVA ion source based on high-voltage surface discharge triggering system was designed, fabricated and tested with copper cathode. The source chamber house was made from a combination of stainless steel and aluminium flanges and three rasin tubes of 56 and 75 mm. Diameters. The cathode is an 8 mm diameter rod surrounded by a stainless ring. The thin pyrex tube is used as an insulator between the cathode and trigger electrode. The anode is an aluminium cylinder. The geometry of the anode-cathode-trigger and the distances between extractor electrodes can be changed easily. Efficient cooling system enables an operation at an are current higher than 400A with repetition rate of more than 1 pps. The arc current of about 0.55 ms pulse width was supplied by 8 sections of LG line which could be charged to a voltage up to 800 V. the trigger pulse of 2 ms sidth and 10 A in amplitude was made on the basis of high step-up ratio tgransformer.

The main arc and plasma ion current-voltage characteristics have been measured. It was found that the plasma ion current did not depend on the geometrical parameter of the anode and decreased very rapidly with the distance from the cathode. The maximum plasma ion saturation current obtained at 20 mm distance from the cathode was 6 A which correspond to the 3% ratio of ion current to arc current. To increase the plasma ion current at a long distance from the cathode, a 2 cm diameter and 15 cm long solenoid was connected to the anode in series. It was found that the plasma ion current was enhanced up to more than one order.

Presented at Asian European Plasma Surface Engineering Conference (AEPSE,99), Peking, China, 14-20 September, 1999.