[en] SILVA process consists in a selective ionization of the 235 uranium isotope, using laser beams generated by dye lasers pumped by copper vapour laser (C.V.L.). SILVA involves power electronic for 3 power supplies: - copper vapour laser power supply, - extraction power supply to generate the electric field in the vapour, and - electron beam power supply for vapour generation. This article reviews the main switches that are proposed on the market or are on development and that could be used in SILVA power supplies. The SILVA technical requirements are: high power, high voltage and very short pulses (200 ns width). (A.C.)

[en] A two-electrode gas switch with a self-breakdown voltage of 100 kV was operated at a pulse-repetition rate of 100 Hz with bursts up to 10 seconds in duration. The output of a pulse transformer provided the (1 - cos wt) waveform which charged the switch in about one-half millisecond. The switch discharged with a peak current of about 10 kA and a total charge transfer of about 10 mC into a damped LC circuit. A continuous purge of air through the interelectrode spacing enabled the switch to recover its breakdown voltage between discharges. Flow rates up to 35 SCFM were employed. This paper discusses the dependence of switch jitter and waveform reproducibility on air-flow rate

[en] Short communications only

[en] The invention refers to power supply systems of poloidal field winding in tokamaks. The purpose of the invention is the extension of functional capabilities of the circuit by means of use of thyristor and diode keys mounted between convertor sections

[en] The LLNL project of the pulsed power system for the National Ignition Facility requires a switch with the following operational parameters: peak current of 400 kA, the transferred charge of 150 C, operating voltage of 25 kV, and reliable operating life of 10,000 shots. A review of high-power switches is given with detailed studies on vacuum switches and semiconductor switches

[en] A novel phenomenon of high frequency modulated electron beam generation is presented. Experiment was carried out with an electron diode having active source of the cathode plasma. Modulated electron beam with duration of > 1μs was generated during more than one hour with a frequency of 2Hz. The frequency of the modulation was found to be > 325MHz. The modulation of the beam current amplitude reaches > 30%. The generation of the modulated electron beam is accompanied by electromagnetic radiation with the same frequency and power of several tens of kW. Based on the experimental data a qualitative model of the observed phenomenon is described

[en] Laser activated semiconductor switches utilize instantaneous response of photoconductivity to turn on or turn off the current through the switch. It has been shown that the semiconductor switch is a good candidate for the fast opening switch applications. With a suitable choice of switch material, for which the carrier recombination time is very fast, the opening time can be as fast as subnanosecond with a very high repetition rate. The semiconductor switches can easily sustain a large voltage and conduct a high current. The authors report on the performance of high voltage operation of GaAs switches. The switches used were intrinsic GaAs and Cr: GaA of bulk devices of millimeter sizes. The range of bias voltage applied was 500 V to 2 kV. The light source was a Q-switched Nd:YAG laser with 10 ns pulse duration. The closing and opening speeds of the Cr:GaAs switches were limited by the rise time and fall time of the laser pulse. Typical off-resistances when the laser light illumination was turned off is higher than 20 MΩ, whereas the on-resistances with laser illumination can be as low as 1 Ω. Such a large ratio of off-resistance to on-resistance allowed switching efficiency of better than 99%

No abstract available

[en] In this paper, we will present our recent results on the research of the ultra-fast high power RF switches based on silicon. We have developed a switch module at X-band which can use a silicon window as the switch. The switching is realized by generation of carriers in the bulk silicon. The carriers can be generated electrically or/and optically. The electrically controlled switches use PIN diodes to inject carrier. We have built the PIN diode switches at X-band, with <300ns switching time. The optically controlled switches use powerful lasers to excite carriers. By combining the laser excitation and electrical carrier generation, significant reduction in the required power of both the laser and the electrical driver is expected. High power test is under going

[en] A fast, efficient and reliable switch is the basic ingredient of a pulse power accelerator. Two switches have been proposed so far: the solid state switch, and the vacuum photodiode switch. The solid state version has been tested to some extent, albeit at low (few kilovolts) level, with risetime around 10 ps in the radial line transformer configuration. The vacuum photodiode is being investigated by Fisher and Rao at Brookhaven National Laboratory. Common to both switches is the need of a short laser pulse; near infrared for the solid state switch, and ultraviolet for the vacuum photodiode switch. Another common feature is the poor energy gain of these switches: the gain being the ratio between the electrical energy switched and the laser energy needed to drive the switch. For the solid state switch, calculations and experimental data show that the energy gain cannot exceed a value between 5 and 10. For the vacuum photodiode, the situation is somewhat similar, unless very high quantum efficiency, rugged photocathodes can be found. A closing switch also can be used to produce short pulses of rf at frequencies related to its closing time, using a well-known device called the frozen wave generator. For a risetime of the order of 30 ps, one could produce several Gigawatts of rf at Xband at very low cost. 12 refs., 12 figs