A high-voltage switching circuit for rapid plasma ion implantation

Summary Form only given, as follows. Efficient ion implantation of metals in a steady-state plasma requires easily adjustable exposure times and shorter duty cycles than those possible by pulsing the sample voltage using conventional spark gap technology. Pulsing the voltage is required to prevent the water-cooled sample from absorbing all the ions and quenching the plasma, since the required sample exposure time is much longer than the plasma ion containment time. Experimental attempts to study the improvement in wear and corrosion resistance of metallic samples are in progress. A high-voltage switching circuit, biased to a negative potential of several tens of kilovolts and using a high-power vacuum tube as the active switching element, has been designed, built, and tested. A square wave from a signal generator is input to a fiber-optic transmitter, which delivers an infrared signal to a fiber-optic receiver. This link provides an isolated control system capable of fast switching speeds. The receiver controls a comparator-actuated, enhancement-mode TMOS switching circuit that pulses a DC-to-DC converter providing a 350-V pulse to the tetrode control grid, turning the sample voltage on and off. A second voltage-regulated TMOS circuit supplies the tetrode filament power (7.1 V, 20 A) from a high-current, 12-V battery.<
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