Long, lifetime, triggered, spark-gap switch for repetitive pulsed power applications

In this article a critical component for pulsed power applications is described: the heavy-duty switch. The design of a coaxial, high repetition rate, large average power, and long lifetime spark-gap switch is discussed. The switch is used with a fail-free LCR trigger circuit. Critical issues for switch design are presented together with experimental results. It is observed that the switch has a good stability, and its lifetime is estimated to be in the order of 1010 shots (~106 C) at 10 J/pulse, 60 kV and 100 ns pulses. Measurements were performed with 20 and 34 kV average switching voltage (100 ns pulses, energy per pulse 0.4 and 0.75 J, respectively). For up to 450 pulses/s (pps), pre-firing can be prevented by increasing the gap pressure (up to 2.5 and 7 bars, respectively), no gas flush is required. Above 450 pps, up to 820 pps, a forced gas flow of maximal 35 Nm3/h, is required for stable operation. Measurements on the time delay and jitter of the switch demonstrate that these values are influenced by pressure, flow, and pulse repetition rate. For 34 kV average switching voltage the time delay and time jitter vary between 35 and 250 and 10 and 80 µs, respectively. For 20 kV average switching voltage these values are: 30–160 and 4–50 µs. During a test run of 2.5 h (at 100 Hz, 0.75 J/pulse) the feasibility of the switch was proved, and the switching voltage jitter was less than 0.7%. ©2005 American Institute of Physic

Apparatus and method for reactive ion etching

The invention relates to an apparatus for reactive ion etching of a substrate, comprising: a plasma etch zone including an etch gas supply and arranged with a plasma generating structure for igniting a plasma and comprising an electrode structure arranged to accelerate the etch plasma toward a substrate portion to have ions impinge on the surface of the substrate; a passivation zone including a cavity provided with a passivation gas supply; said supply arranged for providing a passivation gas flow from the supply to the cavity; the cavity in use being bounded by the injector head and the substrate surface; and a gas purge structure comprising a gas exhaust arranged between said etch zone and passivation zone; the gas purge structure thus forming a spatial division of the etch and passivation zones

Evaluation of pulsed streamer corona experiments to determine the O* radical yield

The production of O* radicals in air by a pulsed streamer plasma is studied by integration of a large set of precise experimental data and the chemical kinetics of ozone production. The measured data comprise ozone production, plasma energy, streamer volume, streamer length, streamer velocity, humidity and gas-flow rate. Instead of entering input parameters into a kinetic model to calculate the end products the opposite strategy is followed. Since the amount of end-products (ozone) is known from the measurements the model had to be applied in the reverse direction to determine the input parameters, i.e. the O* radical concentration

Current multiplication by using multiple thyristors

This paper presents a circuit topology to obtain current multiplication by using multiple thyristors. To gain insight into this technique, an equivalent circuit model is introduced. Proper operation of the topology was demonstrated by experiments on a small-scale setup including three thyristors. One thyristor is triggered by a trigger circuit; the other two are autotriggered and require no external trigger circuit. The three thyristors could be synchronized automatically in sequence. During the closing process, the discharging of the energy storage capacitors via the thyristors is prevented. The discharging starts when all thyristors are closed, and the currents through each thyristor are simultaneous and identical. The output current is exactly three times the switching current. ©2008 American Institute of Physic

Pulse corona discharge in water

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Novel multiple-switch Blumlein generator

The Blumlein generator has been one of the most popular pulsed-power circuits. The pulse forming lines are charged simultaneously, and then discharged via a single switch, such as a spark gap. The generator can be used for single pulse or at a high repletion rate. However, for large pulsed power generation, one critical issue for such a single-switch based circuit topology is related to large switching currents. In this article, we propose a novel Blumlein circuit topology based on multiple switches. The pulsed forming lines are charged in parallel and then are synchronously commutated via multiple switches. No special synchronization trigger circuit is needed for the proposed circuit topology; this robust circuit topology is simple and very reliable. A prototype multiple-switch Blumlein generator with two spark-gap switches has been experimentally evaluated with both resistive and corona plasma loads. In terms of the switching currents, it is observed that the two switches can be synchronized within 2–3 ns. The energy conversion efficiencies are 82% and 76.8% for a matched resistive load and a plasma reactor, respectively