Nobuaki Oshima

Repetitive Pulsed Power Based on Semiconductor Switching Devices

Static induction thyristor and silicon-carbide junction FET have been studied for applications to high-voltage modulators that are demanded by a new type of high-energy particle accelerator, the induction synchrotron. The switching characteristics of these power semiconductor devices are evaluated in order to assess their applicability to MHz level repetitive operation.

Discharge Produced Plasma Extreme Ultra-Violet Source with Hollow Cathode

A pinch plasma has been formed by using a hollow inner electrode with negative polarity. Extreme ultra-violet (EUV) emission was detected from this pinch plasma. The diagnostic results were compared with that obtained with a part of outer electrode was covered with insulator. It is found that the discharge initiated between the hollow cathode and the grounded outer electrode without a creeping discharge. The hollow cathode pinch discharge was operated with energy of ~8.5 J/pulse, indicating potential application for compact EUV source.

Pulsed-power switching by power semiconductor devices

Summary form only given. Repetitive pulsed high-voltage modulators have been developed for industrial applications. They have used the most up-to-date power semiconductor devices such as power MOSFETs, silicon carbide JFETs, static-induction thyristors (SIThy), and semiconductor opening switches (SOS). As a new kind of high-energy particle accelerator, induction synchrotron requires pulsed high-voltage modulators with repetition rate on the order of 1 MHz. A test unit of stacked MOSFET has been successfully developed and tested for continuous operation. In the same time, SIThy and SiC-FET are also investigated for their performance as potential substitutes to MOSFET. A pulsed high-voltage generator using SOS has been developed for applications in sterilization. It consists of a primary unit which is switched by an IGBT and a secondary unit where two magnetic switches and an SOS are used. A pulse transformer is used to multiply the voltage between the two units. The output voltage pulses are of 60 kV in peak value and 50 ns in pulse width, with continuous repetition rate of 1 kHz

Development of Atmospheric Pressure Plasma Jet with Slit Nozzle

A wide flame atmospheric pressure plasma jet has been developed by using a slit nozzle for large area treatment of surfaces. The width of the plasma treated surfaces has been broadened to more than 5 times that obtained by conventional nozzle. The proper function of the slit nozzle towards surface treatment is confirmed by evaluating contact angles of water on polyethylene (PE) surface upon treatment by nitrogen atmospheric plasma jet. A thin film has also been deposited on a glass substrate by introducing hexamethyldisiloxane (HMDSO) into the plasma. The width of the thin film matched with the width of the slit confirming the success of our approach towards attaining a viable large area atmospheric plasma jet for various surface treatments.

Development of nanosecond repetitive pulsed high voltage generator using semiconductor opening switches for atmospheric discharge

Summary form only given. Nanosecond repetitive pulsed high voltage generator is successfully developed for atmospheric pressure pulsed discharge applications. This generator employs an inductive energy storage scheme with SOS (semiconductor opening switch) at the output of generator to sharpen and multiply the output voltage at high repetition rate. The SOS is specially designed semiconductor diode for using as an opening switch. It has a semiconductor p+-p-nn+ structure and is fabricated to obtain a super hard reverse recovery at large reverse current of what is called SOSeffect. The SOS-60-4, which is an assembly of 80 SOS diodes connected in series to obtain withstand reverse voltage of 60 kV, is used in the present systems. It is able to conduct and interrupt high reverse current (up to 4 kA) in very short time (less than 15 ns). To provide forward and reverse current to the SOS at the high repetition rate, MCP (magnetic pulse compression) circuit and IGBT (insulated gate bipolar transistor) is also employed in the present system. The forward and reverse current pulse width is set to be 400 ns and 100 ns, respectively. As a load, a copper plate-edge discharging gap is used. This discharging gap has a length of 30 cm. The gap distance is 1 cm. The tests was carried out and peak forward current of 90 A, peak reverse current of 380 A were obtained respectively. In these results, peak output voltage of 95 kV, voltage rise time of 30 ns and pulse width of 50 ns were respectively obtained at the discharging gap load at 100 Hz repetitive operation. Streamer like discharges were identified at the load