Pseudospark Switch Research Articles

The effect of intermediate electrode on pseudo-spark switch performance with high repetition rate

The effect of intermediate electrode on pseudo-spark switch performance with high repetition rate

Influence of Trigger Injection on Performances of a Single-Gap Pseudospark Switch

Trigger injection and its influence on performances of a single-gap pseudospark switch were studied by using a high-dielectric trigger unit and two types of pulse generators, where pulse parameters, polarity effect, anode voltage, and electrode geometries were varied. It is found that pulses with the rising edge of nanosecond scale can cause diffused electron emission in a large region of the trigger unit, while the slower pulses result in a localized surface flashover. The trigger injection is strongly polarity-dependent, and the way of applying the negative pulse voltage to the outer electrode is more favorable. Not all injected electrons can contribute to the triggering process, and the only factors that can lead to higher charge quantity and energetic components of electrons with a short injection delay are helpful to reduce the trigger delay. A model considering the potential penetration is presented to explain the influence of trigger injection, anode voltage, and electrode geometries. When trigger injection is strong enough or the ratio of cathode hole diameter to its thickness is relatively large, the trigger delay remains constant at different anode voltage; otherwise, it decreases as the anode voltage increases.

High action gas switches.

High action, high voltage closing switches are the key components of pulsed power systems based on high energy capacitor banks, primarily used for high power lasers, electromagnetic accelerators, high pulsed magnetic field facilities, crushing materials, and electromagnetic compatibility tests. There are several options for closing switches, including ignitrons, vacuum switches, pseudo-spark switches, solid-state switches, and high pressure gas switches (spark gaps). Spark switches are currently the most used due to their relatively simple design, reliability, and ease of maintenance and repair. The main disadvantage of spark gaps is a limited lifetime, which is directly or indirectly related to the erosion of the electrodes. To prevent erosion of the electrodes, multichannel switches and switches with movement of the discharge channel were proposed. In this Review, both types of switches are considered.

A Multigap Multiaperture Pseudospark Switch and Its Performance Analysis for High-Voltage Applications

In this article, the development and switching characterization of a coaxial three-gap demountable multigap multiaperture pseudospark switch (MGMA-PSS) prototype is presented. The investigated MGMA-PSS geometry has three gaps which are separated by two cavity drift space regions. A high dielectric constant ferroelectricbased single plasma trigger unit, located within the hollow cathode of the first gap, is used for effective discharge initiation and subsequent synchronous breakdown of the three gaps of the MGMA-PSS. To guarantee long lifetime with high currents and high hold-off voltages and optimized plasma coupling, kidney-shaped ring slot electrodes with baffles are used. Each of the gaps is designed for a minimum voltage hold-off up to 30 kV, with a total voltage hold-off for the MGMA-PSS of approximately 70 kV. Studies of switching behavior are carried out at different operating conditions, such as operating voltages (5-40 kV), hydrogen gas pressures (10-40 Pa), various trigger configurations,and change of circuit parameters [charging capacitance (36, 200, and 380 nF), load resistance(2.7 and 8.3 Ω)]. The short time-scale analysis of the breakdown voltage waveform shows steps in the voltage fall at low gas pressure (<; 20 Pa) and low hold-off voltages (<; 15 kV), which indicates a too-long time delay in plasma formation and coupling within the drift regions. This effect could not be observed at higher voltages (≥15 kV) and gas pressure (≥20 Pa). The overall performance of the threegap prototype PSS has been analyzed in terms of hold-off voltage, fall time, current rise time, peak current, delay time, and related parameters.

Special Features of the Discharge Formation in the Trigger Unit Based on Breakdown Over the Semiconductor Surface in Sealed-Off Cold-Cathode Thyratron

Special Features of the Discharge Formation in the Trigger Unit Based on Breakdown Over the Semiconductor Surface in Sealed-Off Cold-Cathode Thyratron

Development of a Generator of High-Voltage Pulses Based on SOS-Diode and the High-Current Cold Thyratrons with the Auxiliary Glow Discharge for Feeding of Inflectors IC VEPP-5

An Injection Complex (IC) was designed in Budker Institute of Nuclear Physics in Novosibirsk in frame of a program of super high luminosity electron-positron facility VEPP-5. The stability of its operation is determined, among other things, by an injection-extraction system and, consequently, by generators of inflectors. For stable operation of the Injection Complex, these generators must produce pulses with maximum amplitudes of the output voltage of 50 kV and current in the load of the inflector 2 kA, the instability of the flat top less than 5% and its duration in the range from 20 to 92 ns; temporary stability of the generator should be ±2 ns and the output pulse’s front—less than 50 ns. In addition, it must be able to adjust the output voltage amplitude in the range of 10–100% [1]. This paper presents the results of the design sample of a generator of high-voltage nanosecond square pulses based on SOS-diode and the high-current cold cathode thyratrons (pseudospark switches).

Low-pressure discharge in a trigger unit of pseudospark switch

The paper deals with the investigations of the discharge in the trigger unit of the pseudospark switch. The main attention is payed to study of the low-current auxiliary glow discharge, which is sustained in the steady-state mode before triggering, and to rearrangement of this discharge when the trigger pulse is applied to the trigger unit. The hydrogen pressure is varied through a range from 0.08 to 0.25 Torr and the auxiliary discharge current in the electrode system with hollow cathode and hollow anode is up to 40 mA. The estimates for the plasma density in the cathode cavity are provided. Under the action of the trigger pulse, the breakdown between the trigger electrodes occurs and the pulsed breakdown current is intercepted to the main cathode cavity of the switch. It is demonstrated that the process of the current interception strongly depends on the regime of sustaining the auxiliary discharge and on the fact, whether the potential electrode of the auxiliary discharge plays a role of the hollow cathode or the hollow anode.

High-voltage and high-current crowbar system based on pseudospark switches: from system design to verification

This paper presents a high-voltage and high-current crowbar system using pseudospark switches to produce a fast front edge and prolonged pulse current with low ripple amplitude. The crowbar system mainly consists of a main switch, a crowbar switch, an energy storage capacitor, and an inductive load. The basic parameters of the pseudospark switch crowbar system: the storage capacitance is 5 μF, the typical operation voltage is 30 kV, the peak discharge current is about 46.2 kA, the rise time is 4.3 μs, and the pulse duration time is approximately 109 μs, which is nearly 25 times of the rise time. In this paper, we report the timing setting for crowbar system. Experimental results show that crowbar timing should be set slightly after first current maximum, which has a great advantage of increasing the time scale without any reduction in the loss-free peak current. In addition, the pulse current characteristics are also studied. In the research, crowbar inductance Lc and crowbar resistance Rc have significant effects on the ripple amplitude and load current amplitude of pulse current. The experimental results also show that the crowbar current Ic can reach nearly twice of the coil load current Iload with low crowbar inductance Lc. The over-current capacity of the crowbar switch needs to be greater than that of the main switch. The experimental results in this paper can be used to optimize the inductive load current in high-voltage and high-current crowbar system.

Preliminary study of laser-triggered pseudospark switch

Laser-triggered pseudospark switches, also called back-lighted thyratrons (BLTs), are low pressure, high voltage, high current glow-mode switches The feasibility of BLTs is verified. The laser beams with wavelengths of 266 nm and 532 nm were used in the test. In the non-focused mode, the minimum trigger energy for 266 nm laser is 15 mJ, the anode ignition delay time is about 340 ns, and the time jitter is about 40 ns. The minimum trigger energy for 532 nm laser is 83 mJ, the anode ignition delay time is about 420 ns, and the time jitter is about 60 ns. In the focused mode, the minimum trigger energy for 266 nm laser is 4 mJ, when the laser trigger energy is 8 mJ, the anode delay time is 190 ns, the jitter is less than 1 ns. The minimum trigger energy for 532 nm laser is 6 mJ, when the laser trigger energy is 8 mJ, the anode delay time is than 240 ns, the jitter is less than 1 ns. The methods to further reduce the energy of the laser trigger will be studied in the future.

Особенности формирования разряда в узле запуска на основе пробоя по поверхности полупроводника в отпаянном тиратроне с холодным катодом

Особенности формирования разряда в узле запуска на основе пробоя по поверхности полупроводника в отпаянном тиратроне с холодным катодом

Special Features of Parasitic Current Formation in a Sealed-Off Cold-Cathode Thyratron with Trigger Unit Based On an Auxiliary Glow Discharge

Results of investigation of the glow discharge with hollow cathode and ring anode in the trigger unit of a coldcathode thyratron TPI1-10k/50 are presented. A specific feature of the discharge sustainment is that a highly emissive tablet containing cesium carbonate is placed in the cathode cavity. The current-voltage characteristics of the discharge in the trigger unit are obtained for different tablet compositions together with the measured parasitic current to the main cathode cavity. Stepwise transitions to the regime with decreased discharge burning voltage accompanied by an increase in the parasitic current are observed. A model of current sustainment in a hollow-cathode glow discharge is used to interpret the characteristics obtained. Instead of the conventional secondary emission yield, the model uses a generalized emission yield that takes into account not only the ion bombardment of the cathode, but also the emission current from an external source. Based on estimations of the discharge parameters in the trigger unit, a reason for a parasitic current increase is revealed.

Role of Prebreakdown Currents in a Static Breakdown of a Two-Sectioned Cold-Cathode Thyratron

The data on prebreakdown currents and static breakdown voltages measured in two-sectioned sealed-off thyratron with a cold cathode TPI1-10k/50 are presented. The temporal behavior of the anode voltage and of the voltage at the separate sections has been investigated at the prebreakdown and breakdown stages. It is demonstrated that the prebreakdown current presented in the separate sections causes redistribution of the anode voltage between the sections. Due to this effect, a maximum thyratron breakdown voltage can be obtained. The other method to increase the breakdown voltage is based on the forced distribution of the anode voltage between the sections using a capacitive divider. Special features of transition from the prebreakdown to breakdown current are discussed for different thyratron-switching circuits.

Discharge Characteristics of a Pseudospark Switch in Series With a Saturable Inductor

High power pseudospark switches (PSSs) can control pulsed high voltage, high peak current discharges. In this paper, a PSS in series with a saturable inductor at the anode is investigated. The commutation process is analyzed with a time-resolved method. And the effects of the number of magnetic cores and anode voltages on discharge characteristics are studied experimentally. At the beginning of commutation process, when the anode voltage is 10.4 kV with four magnetic cores, the inductor is unsaturated, and there is a flat plateau of the forward voltage drop after the anode voltage drops rapidly to about 200 V, at the same time the current rise rate is 2.8 kA/ $\mu \text{s}$ . When the inductor is saturated, there is a voltage spike that occurs at the end of the flat plateau, and the current simultaneously rises rapidly at the rate of 6.4 kA/ $\mu \text{s}$ . The current sharp rise lags behind the voltage drop of the pseudospark gap, and the electrode erosion and energy dissipation reduce significantly. When the anode voltage is 15.6 kV, the commutation losses reduce by about 30% with seven cores in series at the anode. As a result, it is evident that the discharge process will speed up if the anode voltage is higher. And the trigger delay decreases by up to 8% when the anode voltage varies from 5.2 to 15.6 kV. Finally, in order to obtain a reproducible pseudospark discharge by the use of a saturable inductor, the number of magnetic cores has to be optimized for different anode voltages.

Methods of triggering for the cold-cathode thyratrons with a trigger system based on an auxiliary glow discharge

The paper deals with the investigations of the modernized version of the cold-cathode thyratron TPI1-10k/50 as applied to the problem of nanosecond triggering. The newly developed trigger unit of the device is based on the low-current auxiliary glow discharge with hollow cathode and hollow anode. The regimes for sustaining the auxiliary discharge have been recommended. The characteristic feature of the regimes is that the parasitic current to the main cathode appears due to the ion flow. In such conditions, a rather high hold-off voltage of the device (at a level of 40 kV) is assured. The thyratron with the novel trigger system offers a possibility to use very different methods of triggering. We have proposed and investigated three methods providing the nanosecond stability with respect to the instant at which the trigger pulse arrives to the trigger system. The best results correspond to the case when the jitter in triggering does not exceed of 3 ns.

Design and preliminary experiment of radial sheet beam terahertz source based on radial pseudospark discharge

To satisfy the demands for compact, inexpensive terahertz (THz) sources with power of hundreds of watts, a radial sheet beam THz source which does not require an external magnetic field and is driven by a radial pseudospark discharge plasma electron gun (PSDP-EGUN) is proposed. Radial design has been used in pseudospark switches, but in this paper the design of a PSDP-EGUN to drive a radial THz source is presented for the first time. Being different from the latest reported axial quasi-rectangular sheet beam THz sources driven by an axial PSDP-EGUN, a new design consisting of a circular plate-shaped sheet beam that is directly generated by the radial PSDP-EGUN is reported. As compared to an axial system, the radial configuration may result in a larger beam current and a larger beam-wave interaction area together with a higher potential of THz output power. Theoretical analysis and particle-in-cell simulation have been employed in the design of the radial sheet beam THz source. Output powers in the kilowatt range have been observed in the simulation of this 0.22 THz source. Preliminary experimental results of the radial PSDP-EGUN are also presented.

Features of the discharge ignition in the trigger unit of the cold-cathode thyratron

The sealed-off cold-cathode thyratron TPI1-10k/50 type with a newly developed trigger unit based on auxiliary glow discharge is investigated. As distinct from the commercially produced sealed-off thyratrons, in the thyratron under investigation the high-emissivity tablet is not used. Features of ignition of the trigger discharge are considered. It has been revealed that the delay time to breakdown in the trigger unit and a jitter in the delay time decrease with an increase in working gas pressure. The delay time can be significantly decreased due to availability of the so-called parasitic current in the electrode system of trigger unit. A capability of the thyratron operation with a stability in delay time no more than 4 ns is demonstrated.

Methods of triggering for the cold-cathode thyratron with nanosecond operation stability

The sealed-off cold-cathode thyratron TPI1-10k/50 type with a newly developed trigger unit based on auxiliary glow discharge is investigated. As distinct from the commercially produced sealed-off thyratrons, in the thyratron under investigation the high-emissivity tablet is not used. Different triggering circuits are tested. Circuit for which a delay time to breakdown does not depend on auxiliary discharge current is proposed and tested. A capability of the thyratron operation with a stability in delay time not greater than 4 ns is demonstrated.

Hollow-cathode glow discharge in a trigger unit of pseudospark switch

This paper deals with the investigation of the sealed-off cold-cathode thyratron (pseudospark switch) with a trigger unit that uses a low-current auxiliary glow discharge. As distinct from the commercially produced thyratron TPI1-10k/50, the trigger system of the device under investigation is modernized so that it is able to operate in the absence of the so-called high-emissivity tablet. The data on the principal features of the discharge sustainment in the novel trigger system are obtained. The interpretation of the data is carried out based on the model of the discharge with a hollow cathode, which has been developed as applied to the conditions of the low current densities. It is shown that the regimes of the auxiliary discharge have an impact on the trigger characteristics of the switch. The ability of the switch operation with nanosecond stability with respect to a trigger pulse at high anode voltages is demonstrated.

A novel trigger for pseudospark switch with high repetition rate, low jitter, and compact structure.

This paper presents the design and development of a trigger with a high repetition rate, low jitter, and compact structure for the pseudospark switch (PSS), which includes an improved Marx generator based on avalanche transistors and a corona-plasma trigger unit. The generator adopted a novel 3 × 12-stage Marx circuit based on avalanche transistors in which the failure rate of transistors in the first and second stages was significantly reduced by connecting the parallel capacitors compared to the previous similar generator. The reason for the improved performance was also discussed. The main parameters of output pulses were an amplitude of -7 kV, rise time of 6 ns, jitter of 0.2 ns, and repetition rate of 2 kHz. The corona-plasma trigger unit adopted BaTiO3 ceramics with high εr as the dielectric and was arranged in the hollow cathode of the PSS. The experiments of triggering a PSS prototype were conducted. The influence of anode voltage and pressure on the trigger delay and jitter was studied, and the minimum trigger jitter achieved <1 ns. This trigger worked for 107 shots at the repetition rate of 2 kHz continuously without obvious performance degradation and any failure of the generator. The main advantage of this trigger is the simultaneous combination of the high repetition rate, low jitter, long lifetime, and great simplicity in a compact structure.

A 7.8 kV nanosecond pulse generator with a 500 Hz repetition rate

Pseudospark switches are widely used in pulsed power applications. In this paper, we present the design and performance of a 500 Hz repetition rate high-voltage pulse generator to drive TDI-series pseudospark switches. A high-voltage pulse is produced by discharging an 8 μF capacitor through a primary windings of a setup isolation transformer using a single metal-oxide-semiconductor field-effect transistor (MOSFET) as a control switch. In addition, a self-break spark gap is used to steepen the pulse front. The pulse generator can deliver a high-voltage pulse with a peak trigger voltage of 7.8 kV, a peak trigger current of 63 A, a full width at half maximum (FWHM) of ∼30 ns, and a rise time of 5 ns to the trigger pin of the pseudospark switch. During burst mode operation, the generator achieved up to a 500 Hz repetition rate. Meanwhile, we also provide an AC heater power circuit for heating a H2 reservoir. This pulse generator can be used in circuits with TDI-series pseudospark switches with either a grounded cathode or with a cathode electrically floating operation. The details of the circuits and their implementation are described in the paper.