Three-electrode Spark Gaps Research Articles

Optimization of fast three-electrode spark gaps isolated with a SF6 and he mixture

This paper considered the possibility of reducing the dissipation of the trigger time of the three-electrode spark gaps with a separated triggered electrode. The work is of a theoretical, numerical and of experimental nature. The experiments were performed on a spark gap model under well-controlled laboratory conditions. It was determined that the results obtained with the model can be applied to the spark gap prototype. Unlike the previous research in this area, the computer-designed spark gap that was used can be triggered with one mechanism only. Also, as opposed to the previous study, a mixture of SF6 and He gases and the third electrode with a double ionization effect were used. The obtained results showed the optimal combination of the construction solution, insulation gas, triggered impulse, and the triggered electrode's shape, reduce the stochastic dissipation of a random variable far in the sub-microsecond field. This result is of great significance for the parallel triggering of current and voltage generators to obtain the best superposition signals.

Reliability of three-electrode spark gaps

Two types of three-electrode gas-insulated spark gaps have been investigated in this paper: one with the third electrode located inside the main electrode, and the other with a separate third electrode. Three types of insulating media have been used: vacuum, SF6 and N2. Additionally, three different electrode materials have been implemented: copper, steel and tungsten. The following characteristics have been tested experimentally: the influence of insulating gas parameters on spark gap operation, the influence of the polarity of working and trigger voltages on spark gap operation, and the influence of the rate of rise of the trigger voltage on spark gap operation and the degree of spark gap irreversibility. A theoretical model of the spark gap is presented in the paper, which provides a basis for explaining experimental results depending on specific characteristics of the spark gap.

The effect of electrical parameters on the simulated spark gap discharge current

In this article, the effects of electrical parameters on the spark gap discharge current formation are reported. Using the finite element method to solve for the electric potential and field simulates the discharge process in two- and three-electrode spark gaps using nitrogen gas. The effects of the electrical components on the discharge current buildup and switch closing time for the two switches are investigated. Simulation results for different values of series resistance, capacitance, and inductance are presented for the two-electrode spark gap. In the case of three-electrode spark gaps, the effects of the series resistance, inductance, capacitance, and the resistance and the capacitance of the trigger branch circuit on the discharge current are investigated. The effect of the trigger voltage on the discharge current buildup and arc formation time is also described for the triggered spark gap trigatron. It has been noticed that for both spark gaps the series inductance could severely limit the current buildup rate.

Comparison between the discharge development in the two- and three-electrode spark gap switches

Results of numerical simulation of two- and three-electrode spark gaps operating with pure nitrogen gas are compared. Our result show that in both cases the discharge process evolves via two stages very similar to that was reported in nitrogen glow discharge studies. First, the primary electrons produce positive nitrogen ions; second, the produced ions can disturb the applied field, and can create the space charge region. The undulations observed are because of the secondary effects, in particular, the cathode-directed streamers. The delay time for the three-electrode spark gap is more than that of the two-electrode discharge. Current growth is faster for the two-electrode spark gap in comparison with the three-electrode one. The oscillations are more enhanced for the case of the three-electrode spark gap. Our simulation method provides both temporal and spatial information concerning the operation of such switches. The reported results are helpful in design and optimization of both the two- and three-electrode spark gaps.

Triggered vacuum and gas spark gaps

This paper presents a comparative analysis of the characteristics for the gas insulated three-electrode spark gaps and vacuum insulated three-electrode spark gaps. The experimental part of this paper includes the testing of spark gap models. Two spark gap types were studied: one having the third electrode inside the main electrode and one having a separate third electrode, both being insulated by vacuum or gas (under pressure, providing the same operating voltage as for a vacuum insulated spark gap). Both types of spark gaps were theoretically sized in the optimal way. Several characteristics are determined experimentally: the influence of the gas and vacuum insulation parameters on the spark gap functioning, the influence of the rate of rise and injected energy of the triggering pulse on the spark gap functioning, and the degree of spark gap erosion vs. number of operations (long-time-stability). Two types of gases were applied: SF/sub 6/ gas, N/sub 2/ gas and three vacuum (residual) pressures: 10/sup -1/ Pa, 10/sup -4/ Pa, and 10/sup -6/ Pa. Three electrode materials were used: copper, steel and tungsten. The spark gap switching time and delay time are measured. It was found that the switching time decreases with application of pressure decrease, and the statistical dispersion of switching time raises with the pressure decrease. By comparison of results obtained for the vacuum insulated spark gap and the SF/sub 6/ or N/sub 2/ gas insulated spark gap, it was found that the vacuum spark gap has a slightly shorter switching time and a significantly higher corresponding statistical dispersion.

Triggerable spark gap switches for pulsed gas lasers

Two simple three-electrode spark gaps have been constructed to operate at high voltages up to 30 kV for use in a gas laser triggering system. The performance of each spark gap has been tested in a nitrogen laser system designed for this purpose, and the results are described in this report. The pressure-controlled spark gap has shown better results in terms of stability and lifetime, and it is highly reliable for high repetition rate switching.

Optoisolated control unit for three-electrode spark gaps

An optoisolated driver unit for spark-gap-controlled home-made TEA excimer lasers is described. The unit has been shown to give repetitive discharges of 40 nF capacitors at 30-40 kV in 10-20 ns times without the problems and failures of earlier designs.

Fast Beam Choppers for the Electron-Ring Accelerator

Two beam choppers were constructed which produce an approximately square, 20-ns pulse of 3+-MeV electrons out of the best portion of the 300-ns Astron beam or an 8-?s microwave electron linac beam for injection into the electronring accelerator (ERA) compressor. The choppers are impedance-matched traveling-wave devices which deflect the beam with equal strength electric and magnetic forces, and are powered with either three-electrode spark gaps or thyratrons and a 20-ns pulse line. The electron beam is biased out of the beam-transport system with a dc magnetic field, and switched into it with the chopper.