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Working performances of laser-triggered vacuum switch (LTVS) mainly rely on the interactions of laser with target materials. Influences from target configuration, which is one of key factors in the interactions, are neglected so far. The trigger performances of LTVS with different target configurations are studied in this paper. Relevant influence factors about target configurations are discussed briefly based on theoretical analysis about the trigger process. The test prototype is established based on detachable vacuum chamber. The trigger characteristics of LTVS with different target structures, target depths, and laser focal positions are compared. The relationships between target configurations and trigger performances of LTVS are analyzed and discussed. The preferred targets in LTVS are suggested while considering its lifetime. The test results prove that the conical target shows the best trigger performances compared to other targets. Due to the enlarged laser irradiated area and shortened plasma moving distance, the delay time of LTVS reduces with the decrease in conical target angle and the increase in target depth, while the delay time is controlled within 32 ns. Benefited from laser reflection and plasma collision, the trigger performances of conical targets can be enhanced by focusing laser on the target side surface. In particular, the 90° conical target with 1.5 mm depth is suggested to be employed in LTVS products. [ABSTRACT FROM AUTHOR]

The plasma produced by a pulsed generator is an efficient tool for an airflow control. In this paper, a nanosecond pulsed generator constructed with a fast solid-state switch is designed for triggering synchronous discharges in plasma synthetic jet (PSJ) actuators connected in series. The generator delivers high-voltage pulses with a peak voltage varying from 0 to 20 kV, a rise time of 20 ns, a full-width at half-maximum of 200 ns, and a wide range of pulse-repetition rate varying from 0 to 5.5 kHz. It is proved that this generator is able to trigger synchronous discharges in three PSJ actuators in atmospheric air with a peak discharge current more than 90 A and a deposited energy per pulse of 39 mJ. A schlieren system is used to observe the airflow dynamics, which shows the high synchronization among the three PSJ actuators with a time triggering delay of about 20 ns. The synchronous operation of three PSJ actuators produces a plasma jet with a maximum velocity of 60 m/s and a precursor wave with a velocity of 350 m/s. [ABSTRACT FROM AUTHOR]

With the development of pulsed-power technology, more and more applications require high-voltage and heavy-current pulse switches. Laser-triggered vacuum switch combines laser technology, vacuum switch technology, and three-electrode trigger switch technology, and has the advantages of heavy current capability, good isolation from the main circuit, and short delay time. In this paper, the 1-D thermal conduction model was developed to analyze the influence of laser energy on the velocity of initial plasma. The relationship between the ablation area and the laser energy was derived. The theoretical analysis can be verified by the relationship between the trigger delay time and laser energy and the initial plasma microcurrent curve in the experiments. [ABSTRACT FROM AUTHOR]

Power supplies have played crucial role to improve and extend plasma applications. Several dc, pulsed, and radio frequency (RF) stabilized power supplies have been developed over a wide range of frequencies and voltage waveforms. However, the influence of voltage waveform on the plasma densification, mainly due to the secondary electrons emission from the electrodes, has not been quite explored. This paper proposes an asymmetric pulsed bipolar power supply, adjustable in frequency, amplitude, pulsewidth, and number of pulses for generation of cold plasmas. Short period positive pulses, between longer negative pulses, increase greatly the secondary electron emission from the electrodes and, consequently, the plasma ionization rate. Short pulses (ns) are obtained by the phase shift between each carrier, and the high-intensity pulses are obtained by cascading the cell submodules in a half-bridge cascade topology, using a modular half-bridge converter configuration. The intensity of the positive and negative pulses can be varied independently. There is no unintended dc voltage level between the electrodes, which appear in RF plasmas. The plasma generated in this way is free of electric arc and can be kept stable within a broader range of operating parameters, mainly the voltage and the working gas pressure. [ABSTRACT FROM AUTHOR]

In this paper, a dual-electrode gas switch triggered by ejected plasma is proposed to ensure the switch to be triggered reliably under extremely low switching coefficient. The switch has the configuration of dual electrodes, in one of which a microincentive chamber is embedded to develop ejected plasma into the switch gap, leading to the breakdown of the switch. Both the features of ejected plasma and the triggering discharge characteristics of the switch are studied with different types of gas, gas pressures, voltage polarities, gap distances, triggering pulse energies, and so on. The results show that the switch can be triggered reliably in a much wide working voltage range, as the minimum switching coefficient is low to 9% with the delay time of about 10 \mu \texts . With the decrease of gas pressure and the increase of triggering pulse energy, the height of ejected plasma increases while the delay time of the switch reduces. The polarities of charging voltage and triggering voltage both have obvious influence on the delay time of the switch, and the effect of the former is greater. Under the same gas pressure and triggering pulse energy, the delay time in SF6 is much bigger than that in N2. [ABSTRACT FROM PUBLISHER]

The basic structure and work mechanism of laser-triggered vacuum switch (LTVS) are introduced briefly in this paper, and the processes of primary plasma production and expansion are analyzed as well. A series of experiments has been carried out with different gap voltages, laser wavelengths, laser energies, polarity configuration modes, switch structures, focal lengths, and laser waveforms. The switch structure is modified to improve the heavy-current capability of the switch, and the gap distance is increased to improve the voltage capacity. The special design of the trigger structure can reduce the dependence on the laser energy of the switch and the time delay. A new laser waveform of LTVS multiple wave crests could further decrease the laser energy, and it is the research basis of laser trigger miniaturization and its application in the LTVS. [ABSTRACT FROM PUBLISHER]

A pseudospark switch with two hollow electrodes separated by a ceramic disc in between with a trigger plug inserted near the hole has been fabricated, and it was successfully operated. In this paper, a 29-kV anode voltage, 3.6 kA at 2.2 kHz with 11-ns rise time, has been achieved and operated, successfully. A simple trigger pulse has also been designed, built, and operated effectively reaching more than 1.6-kV trigger voltage that was sufficient to ignite the gas inside the cathode. The main plasma discharge produces 1-ns jitter time that occurred in a reliable manner for more than 6 h of operation continuously. [ABSTRACT FROM PUBLISHER]

Field distortion gas switches are extensively used in pulsed power systems. Switch performance typically degrades because of electrode erosion, which directly influences the output parameters, stability, and reliability of pulsed power systems. With the same value of $pd$ , different pressure and gap lengths in gas switches can affect electrode erosion property and thus, the subsequent performance degradation, but few results have been published. In this paper, repetitive discharges have been undertaken in a three-electrode field distortion gas switch with fixed pd$ to study the influence of pressure and gap length on electrode erosion and switch performance. The morphology of electrode surface and time histories of both trigger jitter and the probability of prefire have been investigated during the whole life cycle of the gas switch. The results show that when pd$ is fixed, high pressure and a short gap make for low trigger jitter at the start of the switch life cycle but lead to more severe electrode erosion, expediting the degradation of performance in field-distortion gas switches. Meanwhile, the probability of prefire increases rapidly with the increase of pressure. [ABSTRACT FROM PUBLISHER]

This paper demonstrates for the first time the use of microplasma to perform AND, OR, and XOR logic operations. The logic circuits are implemented similar to diode-resistor logic. Output voltages are in the range of \(5-40\) V and can be modified by varying the load resistor. The active area of the microplasma device is just \(50~\mu \) m \(\times 5~\mu \) m. The small interelectrode gap kept breakdown voltage to \(\sim 250\) V when operated in He gas at atmospheric pressure. The use of plasma as a source of free carriers is also demonstrated, with free carriers available up to 500- \(\mu \) m away from plasma. [ABSTRACT FROM PUBLISHER]

This paper provides analysis of experiments aimed at defining the capabilities of plasma opening switch (POS) for energy transfer to a load of inductance comparable with the inductance of the energy store vacuum section. The analysis is performed using the substantiated technique that allows quantitative estimation of the POS efficiency. Under the same conditions with a conduction current of ∼1 MA and POS voltage of ∼1 MV, the energy transferred to the load depends strongly on the transmission line design. When the electrode gap in the line is ∼1 cm, the energy delivered to the load is ∼40 kJ. Increasing the gap to ∼4-cm increases this energy to ∼100 kJ. [ABSTRACT FROM PUBLISHER]

Reducing the working coefficient of gas switch can effectively lower the prefires probability. This paper discusses in detail the discharge characteristics of a three-electrode plasma-jet triggered gas switch (PJTGS), especially at low working coefficients. The triggered discharge process of the PJTGS is analyzed. Plasma jets are observed and discussed with respect to trigger voltage, trigger energy, and gas pressure. In addition, the switch jitters at different conditions are investigated, including ground resistor, charging voltage, trigger energy, trigger voltage, and working coefficient. The results indicate that the height of the plasma jet increases with the increase of trigger voltage and energy, and decreases with the increase of gas pressure. At working coefficients higher than 75%, trigger voltage of +80 kV, and ground resistor of 100 \(\Omega \) , reliable subnanosecond jitters can be obtained with the charging voltages of ±25, ±30, ±40, and ±50 kV. When the working coefficients are between 50% and 28.1%, the switch jitters range from 1.6 to 3.5 ns. Even at the working coefficient of 28.1%, the PJTGS can still be triggered reliably with a switch jitter of 3.5 ns. [ABSTRACT FROM AUTHOR]

Pseudospark switches are fast-closing low-pressure gas discharge switches with a hollow-cathode geometry. They can be triggered optically or by electron injection, where electrons emitted from a cold cathode emitter are accelerated in the electric field and initiate breakdown. The efficiency of charge carrier accumulation in the hollow-cathode structure determines the performance of the switch operation. The advantages of such switches include high hold-off voltage, high conduction current, fast current rise time, low delay and jitter time, and long lifetime. In this paper, the operating characteristics of a pseudospark switch, triggered by a carbon-nanotube (CNT)-coated electron emitter, are presented. The electron emitter is fabricated by coating randomly oriented CNTs on silicon substrate using chemical vapor deposition method. Field emission characteristics of CNTs are determined and then used as part of the trigger electrode which is integrated into an in-house constructed pseudospark switch. The operating characteristics of the switch are tested under different background pressures and different trigger voltages. Delay and jitter time under different working conditions are analyzed. Hold-off voltage and current rise time are also presented. [ABSTRACT FROM AUTHOR]

The triggering discharge behavior of the rail gap influences the jitter of discharge delay and inductance of the spark switch due to the formation of multiple spark channels in the rail-gap switch, which is related with the development of avalanche in the discharge process under the nanosecond triggering pulses. In this paper, the PIC/MCC method is used to investigate the avalanche development under a triggering pulse. A model of intershielding is proposed in the PIC/MCC method considering the effect of the space charges. From the simulation and experimental results, it has been clarified that the avalanche process can be controlled by the statistical delay time of the effective primary electrons. The intershielding model can also explain the effect of the rise time of a triggering pulse on the avalanche development. [ABSTRACT FROM PUBLISHER]

It is our interest to design and develop a high-power pulser system employing an electrical discharge in a spark gap. The type of discharge generates short electric pulses capable of both the characteristics of a fast rise time and a high repetition rate. Such a switch pulser has wide applications in the industry. To generate the electrical discharge in the spark gap in an efficient manner is very important for the switching operation. The regime of the operation utilizes the residual plasma in the interpulse recovery of the spark gap to increase the repetition rate. Therefore, the mechanisms of the discharge in a controlled manner following the electrical breakdown of the spark gap, such as the plasma generation in the spark channel and the dielectric recovery process as well as the residual plasma in the post-spark-discharge period, are of great importance. The understanding of the type of the spark-gap discharge for the switching at a high repetition rate beyond 1 MHz has been the primary goal. The typical voltage and current ratings are below 1 kV and several amperes, respectively. In particular, this paper addresses the optimal set of several parameters, such as the spark-gap geometry, electrode gap distance, gas pressure, and gas type, in conjunction with a unique circuit scheme to drive the discharge in the controlled fashion. [ABSTRACT FROM PUBLISHER]

In this paper, a novel six-channels annular plasma-jet chamber is designed and embedded in the trigger electrode of the three-electrode gas switch to generate multichannel plasma jets without air flow, which is used to trigger the gas switch to form multichannel discharge. Results of this paper show that the plasma-jet triggering can be conductive to steady formation of multichannel discharge. [ABSTRACT FROM PUBLISHER]