Schematic diagram of arc discharge apparatus used in present experiment: (a) a vacuum outlet, (b) gas inlet, (c) indicators of pressure and vacuum gages, (d) cathode inlet and outlet coolant water, (e) sealed quartz window, (f) high purity copper shaft coating with nickel layer, (g) high purity copper tube isolated from the chamber, (h) feed through, (i) lead screw, (j) steeper motor, (l) sealed flange cover, (m) stainless steel chamber, and (n) copper pipe for water coolant.