An improved design of the gas switch for Marx generators of the stand-300 installation

An improved version of the gas spark-gap switches intended for voltages up to 200 kV (the bipolar charging up to ±100 kV) and switching currents of up to 100 kA is designed for Marx generators of the Stand-300 installation (National Research Center Kurchatov Institute). The new design is based on the existing spark-gap configuration of P-200 switches with two toroidal electrodes and a trigger electrode as a thin disk with a hole, which is located between them (“field distortion” scheme). The design of the insulating body of the switch was modified for attaining a more uniform voltage distribution, reducing the normal component of the electric field on the insulator surface, and simplifying the gas-switch design as a whole. The measured characteristics of the new gas switch are in a good agreement with the calculated ones for the selected geometry of the spark gaps.     

High-voltage high-current air-filled spark gaps of an artificial-lightning-current generator

The designs of two high-voltage high-current air-filled spark gaps of an artificial-lightning-current generator-a two-electrode ДMBP-5 gap for a voltage of up to ±5 kV with graphitized-carbon electrodes and a three-electrode TKBP-50 gap for a voltage of up to ±50 kV with steel electrodes—are described, and their main switching characteristics and the results of tests are presented. Tests were performed with a ДMBP-5 spark gap that switched the normalized long C lightning-current component with an amplitude of up to 0.85 kA, a rise time of up to 0.77 × 10⁵ A/s, a maximum duration of 1000 ms, and a transferred electric charge of up to 210 C. When a TKBP-50 spark gap was used, the normalized pulse A lightning-current component with an amplitude of up to 212 kA, a rise time of up to 7 × 10⁹ A/s, a maximum duration of 500 μs, and an action integral of up to 2.07 × 10⁶ A² s was switched.     

A trigger generator for controlling a high-current triggered vacuum switch

A trigger generator (TG) with a discharge of a storage capacitor through the trigger gap of a triggered vacuum switch (TVS) was developed. It provides a voltage amplitude of up to 7 kV across the trigger gap. After a gap breakdown, the TG provides an ignition current in the form of a damped sinusoid with an amplitude of ≥1 kA. It differs from analogous devices by pulsed charging of the storage capacitor and the use of an output self-breakdown gas-filled switch. The developed design of the gas switch with gas preionization in the spark gap by an additional corona discharge provides high stability of both the pulsed-breakdown voltage and the switching-on time. The TG tests showed reliable and stable switching-on of high-current TVSs of different modifications with a discharge-current rise rate of up to 3 × 10¹⁰ А/s.     

A compact, low jitter, nanosecond rise time, high voltage pulse generator with variable amplitude

In this paper, a compact, low jitter, nanosecond rise time, command triggered, high peak power, gas-switch pulse generator system is developed for high energy physics experiment. The main components of the system are a high voltage capacitor, the spark gap switch and R = 50 Ω load resistance built into a structure to obtain a fast high power pulse. The pulse drive unit, comprised of a vacuum planar triode and a stack of avalanche transistors, is command triggered by a single or multiple TTL (transistor-transistor logic) level pulses generated by a trigger pulse control unit implemented using the 555 timer circuit. The control unit also accepts user input TTL trigger signal. The vacuum planar triode in the pulse driving unit that close the first stage switches is applied to drive the spark gap reducing jitter. By adjusting the charge voltage of a high voltage capacitor charging power supply, the pulse amplitude varies from 5 kV to 10 kV, with a rise time of <3 ns and the maximum peak current up to 200 A (into 50 Ω). The jitter of the pulse generator system is less than 1 ns. The maximum pulse repetition rate is set at 10 Hz that limited only by the gas-switch and available capacitor recovery time.     

Capacitor units with air insulation for linear transformers

The design of two capacitor units intended for use in high-power pulsed generators is described and the results of their tests are presented. Each unit is an assembly consisting of a multichannel spark gap and two capacitors with a total capacitance of 80 or 16 nF and a charging voltage of up to 100 kV. The use of air at atmospheric pressure as the insulating and working medium of the spark gap is a feature of the capacitor units. The following parameters of the output pulses were obtained at a resistive load for the 80- and 16-nF units: currents of ～48 and ～20 kA, voltages of ～55 and ～52 kV, and times of energy deposition into the load of ～140 and ～60 ns, respectively. A model for numerical calculation of the transient discharge process in the capacitor units is presented and the influence of the capacitance of the capacitors and the number of spark channels in the spark gap on the parameters of the generated pulse is analyzed.     

An experimental setup for investigation of arc and erosion processes in high-voltage high-current breakers

An experimental test setup for investigating arc and erosion processes in gas-filled high-voltage high-current switches is described and some results that were obtained on it are presented. The setup includes a discharge chamber that allows simulation of the process of disconnecting the ring and pin contacts, a capacitive energy storage with a capacitance of 0.11 F and a charging voltage of up to 10 kV, and a remotely controlled gas-supply system. The diagnostic complex includes systems for measuring the discharge current, the voltage across the arc, and the pulse pressure in the chamber, as well as high-speed filming and optical spectroscopy. Experiments with a current amplitude of 30–300 kA can be performed on the test bench. During the first current half-period of 1.0–3.0 ms, the contacts move apart to a distance of 3–4 cm. The arc is cooled via transverse gas blowing at a pressure in the chamber of 0.5–1.5 MPa. A movable contact is displaced due to the pressure of the gas that is pumped into the chamber.     

Mega-ampere submicrosecond generator GIT-32

The GIT-32 current generator was developed for experiments with current carrying pulsed plasma. The main parts of the generator are capacitor bank, multichannel multigap spark switches, low inductive current driving lines, and central load part. The generator consists of four identical sections, connected in parallel to one load. The capacitor bank is assembled from 32 IEK-100-0.17 (0.17 microF, 40 nH, 100 kV) capacitors, connected in parallel. It stores approximately 18 kJ at 80 kV charging voltage. Each two capacitors are commuted to a load by a multigap spark switch with eight parallel channels. Switches operate in ambient air at atmospheric pressure. The GIT-32 generator was tested with 10, 15, and 20 nH inductive loads. At 10 nH load and 80 kV of charging voltage it provides 1 MA of current amplitude and 490 ns rise time with 0.8 Omega damping resistors in discharge circuit of each capacitor and 1.34 MA530 ns without resistors. The net generator inductance without a load was optimized to be as low as 12 nH, which results in extremely low self-impedance of the generator ( approximately 0.05 Omega). It ensures effective energy coupling with low impedance loads like Z pinch. The generator operates reliably without any adjustments in 40-80 kV range of charging voltage. Maximum jitter (relative to a triggering pulse) at 40 kV charging voltage is about 7 ns and lower at higher charging voltages. Operation and handling are very simple, because no oil and no purified gases are required for the generator. The GIT-32 generator has dimensions of 3200 x 3200 x 400 mm(3) and total weight of about 2500 kg, thus manifesting itself as a simple, robust, and cost effective apparatus.     

High-Voltage Spark Gaps for Technological Purposes

High-power untriggered spark gaps intended for operation at a voltage of up to 150 kV and a current of 10 kA have a service life of up to 10¹¹pulses. The spark gaps ensure switching to a load for 5–20 ns with a pulse repetition rate of up to 400 Hz. They operate under atmospheric pressure without blowing-through in an installation for decontaminating processing of products with high-voltage pulses.     

Multichannel Spark Gaps with Control Bar Electrodes: Their Development and Application (A Review)

Multichannel low-inductance (1 nH) gas-filled spark gaps (MSGs)¹ with several tens of channels each, bar control electrodes designed for an operating voltage of 100 kV, and a switched current of up to 400 kA are reviewed. The control electrodes, made in the form of narrow thin plates, have an intermediate potential, are positioned in the gap between two common main electrodes (high-voltage and low-voltage (grounded)), and are oriented uniformly along their length. Upon a near-simultaneous change in the bars' potential in a time of <15 ns, applying a signal through trigger circuits disturbs the electric-field distribution in the gas volume. The field strength sharply increases at the electrode surfaces and especially at the edges of the bars, from which breakdowns develop synchronously from one electrode to another or simultaneously to both main electrodes. When the discharge formation is completed, the main electrodes of the MSGs are short-circuited by discharges through parallel channels (whose number is equal to the number of bars). These switches ensure the nanosecond accuracy of the operation delay relative to the trigger pulse at a breakdown-strength margin of up to 100%, determined by the pressure (>0.1 MPa) of the MSG-filling gas. Electrical circuits for initiating the discharge development in the MSGs, the transients in such circuits, and the factors affecting the parameters of processes and the gap-breakdown delay and rate are considered. Particular MSG designs, multicable systems for parallel triggering of a large number of MSGs, and the use of 48 four-channel 50-kV MSGs in the first iron-free LIA-2 linear electron accelerator (2 MeV, 25 kA, and 60 ns) created in 1967 are described. The successful operation of MSGs stimulated further studies and the development of efficient trigatrons for operating voltages of 100 and 500 kV. Up to 3000 MSGs of this type are used in new high-power linear electron accelerators. A low-impedance (0.45 ) generator of high-voltage pulses (50–200 kV) with a multicable output has been developed to synchronously trigger such large numbers of trigatrons as these.     

Electrospark Dispersion of Metal Nanopowder

The production of electrically conducting metal nanopowder by electrospark dispersion in liquid dielectric is considered, in the case with a significant overvoltage in the discharge gap between the electrodes. An experimental apparatus with an air gap that creates an overvoltage at the working spark gap is developed. The two gaps split the voltage on capacitor discharge.     

Experimental study of fine center electrode spark plug in bi-fuel engines

In the present work, the erosion of platinum fine center electrode spark plugs and conventional nickel plugs are investigated in a gasoline and natural gas bi-fuel engine. The effect of electrode erosion is evaluated by comparing the required ignition voltage and cold start ability of the different plug designs. After durability tests, platinum fine center electrode plug had insignificant electrode erosion and negligible gap growth; whereas the nickel plug had notable erosion and gap growth. There was no detectable side sparking for fine center electrode plugs. In terms of performance, the required ignition voltage of fine center electrode plug was lower than conventional spark plug. Also, results of a cold start test demonstrated that the starting time of the engine with fine electrode plugs was lower than conventional spark plugs. The surface of electrodes was studied by the scanning electron microscope and the energy dispersive X-ray spectroscopy techniques. Cracking and peeling was observed on the surface of the nickel conventional electrodes, but not on the surface of the platinum fine electrodes. These tests show that platinum fine center electrodes could be suitable for gasoline/natural gas bi-fuel engines to meet long lifetime demand.     

Study on erosion mechanism of graphite electrode in two-electrode spark gap switch

In a high-powered single pulse system, the graphite electrode is better than other common metal electrodes for high energy transfer and pulse discharge. In this paper, the erosion mechanism of graphite electrode is investigated with the thermodynamics theory and the experimental results. Based on a simplified mathematical model, the graphite electrode erosion process of high-powered spark gap switch is also analyzed. The analysis results show that the relationship of the graphite electrode erosion and the charge transfer is linear, which is accordant with the experimental results.     

A megavolt frequency generator pulses with an FWHM duration of 30 ns

A generator of a pulse voltage with an amplitude of up to 1 MV based on a ten-stage voltage multiplier is described. The generator contains a control panel, a unit for periodical triggering of spark gaps in the generator stages, and a rectifier outputting a voltage of ± 50 kV for charging capacitors in stages. The generator has an output discharge capacitance of 500 pF, a stored energy of 250 J, a self-inductance of <0.7 μH, a guaranteed service life of 10⁵ charging-discharging cycles, a rise time of the first voltage half-wave of 15 ns at a load of 200 pF, and a repetition rate of 1 Hz. To reduce the self-inductance of the source, insulating housings of capacitors and spark gaps are used in its layout.     

The lifetime of a high-current triggered vacuum switch with multi-gap

Triggered vacuum switch (TVS) synthesizes the merits of spark gap and vacuum technology. A TVS sample with multi-gap is described in this paper, in which the main electrode is made up of spatially inter-leaved rods of opposite polarity on a ring. Three pairs of rods are adopted, which can form six main gaps, promoting the high current carrying ability evidently. Due to hundreds of high current pulses, the influence of vacuum arc to the trigger pin and main electrode is inevitable, leading to the termination of lifetime of TVS, especially in the erosion of trigger pin and arc deposition on the trigger surface. In this paper, the major influence factors of lifetime are analyzed and it is concluded that the main current arc is the key factor to determine the lifetime of TVS. As well the change of trigger voltage, trigger resistance and trigger delay will predict the termination of TVS lifetime.     

400-kV trigatrons for high-power low-inductance pulse generators

A series of four-channel trigatrons operating at a voltage of up to 400 kV and a current of 280 kA per channel have been developed and tested. The control electrode is coaxially arranged in a hole of the main (positive) high-voltage electrode. This design ensures a small spread (jitter) of the operation delay time (Δt _d < 1 ns) for the discharge gap filled with elegas (SF₆). The electric strength of lateral surfaces of the device body is increased without using dielectric fluids. The service life of switches is increased by using tubular metal (steel) screens in the working volume. For the parallel operation of trigatrons, the Δt _d value is also below 1 ns, but it sharply increases if the gap between the main electrodes exceeds 11–12 mm.     

A ГИН-1200 high-voltage pulse generator

The electric circuit, design, and electric and triggering characteristics of the ГИН-1200 small-sized 12-stage high-voltage pulse generator used for charging a double forming line to 1 MV for a 300-ns period are described. The generator is mounted in a metallic housing with the transformer-oil insulation. The storages in stages of the generator are KMK 100–0.017 (100 kV, 0.017 μF) capacitors with a 1-kJ total stored energy. The switches are trigatron gaps filled with a 20% SF₆ + 80% N₂ gas mixture. The gap housings are assembled into one line. The through-passing axial channel ensures spark illumination of adjacent intervals, thereby improving the triggering characteristics of the generator. The operation-time scatter of the ГИН-1200 generator at an 85-kV charging voltage and 65% electric-strength margin was ≤10 ns, and the operation delay time was ～100 ns. The ГИН-1200 generator operated ～2000 times and demonstrated reliable stable operation.     

A shaper of multiply repeated picosecond high-voltage pulses in a range of 10<Superscript>−10</Superscript> s

A pulse-shaping device is described that reproduces multiply repeated picosecond high-voltage pulses with a duration of 10^?10 s, an amplitude of >100 kV, and a repetition rate of up to 10³ Hz. The principle of switching the circuit using a single spark gap filled with a compressed gas instead of conventional spark peakers and a chopping gap, connected in series, is applied. The use of compressed hydrogen at a pressure of 30 atm as the working gas favors stability of the discharge voltage and a virtually unlimited lifetime of the shaping device.     

A High-Current Pulse Generator SIGNAL with an Inductive Energy Storage and a Microsecond Plasma Opening Switch

The primary energy storage in the SIGNAL installation is a 4.7-F capacitor bank with a stored energy of up to 24 kJ switched by a gas-discharge gap switch of the trigatron type. The plasma source and the design of the microsecond plasma opening switch ensure current flow through this switch and inductive storage for a time of up to 1.7 s. The current amplitude reaches 330 kA. The current switched to the load is 20–300 kA in various modes with a rise time of 10–200 ns. The voltage across the feedthrough insulator reaches 400 kV. The installation is used in experimental studies of linear pinches, capillary discharge, and microsecond plasma opening switches.     

An accelerating voltage generator for compact pulsed neutron sources

A multistage generator of high-voltage pulses with a scroll geometry of spark switches, which is produced according to the Marx scheme, is presented. The device is designed for a small pulsed neutron source and makes it possible to obtain accelerating-voltage pulses with amplitudes of up to 450 kV at a stored energy of up to 50 J and a load current of up to 1.5 kA.     

A Shielded 800-kV Pulse Generator at an Energy of 32 kJ

The electric circuit, design, and characteristics of a shielded oil-insulated Marx pulse-voltage generator (PVG) with a stored energy of 32 kJ and an output voltage of 800 kV are described. The PVG charges a water-insulated forming line of the STRAUS-R accelerator of a pulsed electron beam to 700 kV within a time of <1 μs. Two И ЭПM-100-0.4 УXЛ 4 capacitors are installed in each of its eight stages. The switches of the three first stages are 100-kV trigatrons filled with a 40% SF₆ + 60% N₂ gaseous mixture to a pressure of 0.7 MPa. The switches of the other stages are two-electrode spark gaps. The PVG-operation delay time is 108 ± 5 ns at a breakdown-strength margin of each spark gap of ∼80%. The PVG-circuit inductance is ∼1.4 μH. The overall dimensions of the PVG's steel tank are 2400 × 800 × 800 mm (without an output device); the PVG mass is 1700 kg. __________ Translated from Pribory i Tekhnika Eksperimenta, No. 6, 2005, pp. 21–27. Original Russian Text Copyright ? 2005 by Gerasimov, Gordeev, Kul'gavchuk, Myskov, Nazarenko, Pavlov, Sofronova, Suvorov, Shejnov.