Development of high-current pulsed heavy-ion-beam technology for applications to materials processing

Development of intense pulsed heavy ion beam technology for applications to materials processing is described. We have developed a magnetically insulated ion diode for the generation of intense pulsed metallic ion beams in which a vacuum arc plasma gun is used as the ion source. When the ion diode was successfully operated at a diode voltage of 220 kV and a diode current of 10 kA, an ion beam with an ion current density of >200 A/cm2 and a pulse duration of 40 ns was obtained. The ion composition was evaluated by using a Thomson parabola spectrometer, and the ion beam consisted of aluminum ions (Al(1-3)+) with an energy of 140 - 740 keV and protons with an energy of 160 - 190 keV; the purity was estimated to be 89%, which was much higher than that of the pulsed ion beam produced in a conventional ion diode. The development of a bipolar pulse accelerator (BPA) was reported in order to improve the purity of intense pulsed ion beams. A double coaxial type bipolar pulse generator was developed as the power supply of the BPA. When a bipolar pulse with a voltage of ±90 kV and a pulse duration of about 65 ns was applied to the drift tube of the BPA, the ion beam with an ion current density of 2 A/cm2 and a pulse duration of 30 ns was observed 25 mm downstream from the cathode surface, which suggested bipolar pulse acceleration.