Gas Switch Research Articles

Bionic modified atmosphere film Inspired by plant stomata with curcumin as controllable gas “Switches” for fruit preservation

Modified atmosphere packaging (MAP) is a promising preservation technology for the fruits with the characteristics of respiration metabolism. However, traditional MAP cannot precisely control and regulate the selective permeation of gas. Inspired by the fact that plants control respiration through leaf stomata, we innovatively construct a bionic intelligent MAP of curcumin-porous starch/chitosan (Cur-PS/CS) with leaf stomata structure. Herein, PS is used as the bionic stomata, and Cur is used as the gas switch controlled by changing the pH and temperature. As a result, the CO2/O2 selectivity values are precisely controlled from 2.60 to 5.51 by controlling the amount of Cur released from PS. In which, the 10.3 % Cur-PS/CS displays the highest CO2/O2 selectivity value (5.51). In addition to outstanding tensile strength (51.54 MPa) and antioxidant activity (91.03 %), the inhibition zone diameters of 10.3 % Cur-PS/CS film against Escherichia coli, Staphylococcus aureus and Aspergillus niger reach 8 mm, 7.8 mm and 9.1 mm, respectively. Therefore, the 10.3 % Cur-PS/CS film effectively extends the shelf life of the non-climacteric fruit (cherries) and climacteric fruit (apple slices). More importantly it does not bring any issues with food safety and environmental contamination due to the excellent biodegradability of Cur-PS/CS film.

Methodology for measuring the energy characteristics of two-electrode gas discharge plasma switches in the picosecond range using the reflectometry method

This research proposes a new technique for measuring the energy characteristics (losses of energy in the spark gap, related to light radiation, ionization, excitation, and heating of the working gas during the development of plasma; discharge power) of two-electrode gas dischargers in the subnanosecond range. The work examines the voltage waveforms across the discharge gas gap and the discharge current waveform obtained by the reflectometry method in the subnanosecond range. To do this, the traditional technique for measuring such characteristics was modified. This allows us to restore the back edge of the voltage pulse across the discharge gap at the breakdown delay and the breakdown stages, which is usually lost in the subnanosecond range when measuring such waveforms. For modification, calculated data on the ionization frequency were used. This allows us to replace the plasma of the discharge gap with a constant resistor in those sections of the voltage waveform where the characteristic ionization time is more than an order of magnitude longer than the duration of the voltage pulse applied to the gap. The waveforms of the voltage across the discharge gap and the discharge current obtained in this way allowed us to calculate the power dynamics and total energy introduced into the gas discharge plasma. These parameters are important both for calculating the efficiency of gas switches and for other applications of gas discharge plasma, in particular laser pumping.

A compact solid-state high repetition rate trigger based on a spiral generator.

The trigger generator made with a spiral generator (SG) has the advantages of light weight, compact structure, and low cost and has promising applications in the pulsed power field. This paper introduces a compact solid-state high-voltage pulse trigger system based on an improved SG, which has improved repetition rate and lowered the demands for semiconductor switches' maximum current and current rise rate when compared with previous studies. The improvement is achieved by winding outward an additional layer of the passive layer and low-voltage metal strip, which realizes a significant reduction of the peak current and current rise rate of the discharge switch. The final dimension of the trigger is 25 × 10 × 10cm3, excluding the power supply. An experiment carried out in single shot mode shows that the peak value of the output pulse can reach 50kV with a leading edge of 57ns. Repetitive experiments were carried out up to 1kHz, with the peak voltage of the output pulse being 30.5kV, the leading edge being 48ns, and the jitter being 0.84ns. Finally, the generator is used to trigger a gas switch, and it works stably and reliably.

A novel micro-capillary discharge plasma jet triggered gas switch.

To reduce the working coefficient and jitter of the three-electrode gas switch used in linear transformer drivers, a novel trigger method that uses a nanosecond pulse in cooperation with the microplasma jet generated by capillary discharge was developed. A microplasma jet was generated by the nanosecond trigger pulse and injected into the follow-up breakdown gap of the gas switch to decrease the working coefficient. The influence of capillary parameters on the development of the microplasma jet was simulated. The results showed that the microplasma jet significantly reduced the breakdown delay time, jitter, and working coefficient. Increasing the capillary length and decreasing the diameter results in better triggered breakdown performance. Furthermore, the gas switch triggered by a positive pulse exhibits a lower breakdown delay and jitter. Combined with the intensified charge coupled device's shooting results, it can be concluded that the microplasma jet has a distinct influence on streamer formation, which is important for improving the working performance of the gas switch.

Design and characteristics of a fiber laser powered repetitive micro-plasma jet triggered gas switch.

To satisfy the need for low jitter in gas switches at repetition rate and enhance insulation reliability during high voltage operation of the trigger, we propose a micro-jet triggering system. This system requires less energy and can use a laser power supply as an energy source. It effectively improves the insulation stability of the trigger when working at high potentials and achieves a good triggering effect with low jitter at low working coefficients. The breakdown characteristics were tested by double-pulse experiments. Ensuring the same operating conditions for both pulses, the pulse interval was varied to obtain the breakdown voltage dispersion at different repetition rates. The results indicate that the dispersion of the breakdown voltages can reach 0.16% at a frequency of 50Hz with a pulse front of 30 μs, representing an order of magnitude reduction compared to the 1.45% at switching self-breakdown, and decreases further as the air pressure rises. In addition, the size of the microcapillary has an impact on the dispersion of breakdown voltage. It was found that for a range of lengths from 2 to 6mm and aperture sizes from 80 to 400μm, the trigger jitter was lower when the length was larger and the aperture was smaller. Furthermore, a trigger life test was performed on the ceramic capillary, and after one million triggers, the system remained stable with no degradation in trigger performance.

Experimental results of a 330 GW impedance-matched Marx generator

Impedance-matched Marx generators (IMGs) are considered next generation pulsed-power drivers because of their long lifetime (> 10,000 shots), repetition rate (> 0.1-Hz), fast rise time (~ 100-ns), and high-energy-delivery efficiency (~ 90%). “TITAN” is a 14-stage IMG designed to deliver 1-TW to a 2-Ω matched load. In this paper, design, simulation, and experimental results for six stages of TITAN including its triggering system, air delivery system, and pulse shaping are presented. To achieve efficiency over 85% and maximize the capability of an IMG, synchronized triggering, reduced pre-fire rate, and pulse shaping ability are crucial. In this paper, novel engineering solutions are introduced, tested, and proven to overcome those challenges. 6-stage TITAN, powered by 102 identical bricks and 102 field-distortion-triggered gas switches, could generate ~ 600-kA and ~ 700-kV across a ~ 0.9-Ω matched load when fully charged to ± 100-kV. In these experiments, 6-stage TITAN is tested up to ± 70-kV charge voltage which delivers a peak power of 330-GW to a 1.2-Ω resistive load.

Repetitive high-power discharge operation of a micro-laser triggered gas switch.

A low-energy, diode-pumped, solid-state passively Q-switched laser operating at a wavelength of 1535nm has been demonstrated to trigger gas switches. This technology has the potential to bring significant improvements to the operation and reliability of compact pulsed power drivers. Compact pulsed power drivers are often required to operate for hundreds to thousands of shots without maintenance; thus, the reliable operation of the laser triggered switch is significant for the adoption of this technology. A primary limiter of spark gap lifetime is electrode erosion. In the case of a laser triggered switch where the laser is focused on one electrode, an additional source of erosion is the direct ablation of the electrode material by the laser. The micro-laser used in the previous experiments is very low energy, but over thousands of shots, it does damage directly to the target electrode. This damage could potentially interact with the erosion due to the current discharge and impact the operation of the switch. The focus of this paper is to describe experiments undertaken to assess this damage and quantify its effect on switch operation over many discharges at current and energy levels relevant to compact pulsed power systems.

Study of operation mode and breakdown characteristics for multi-stage gas switch

Multi-stage gas switches (MSGSs) are widely used in megavolt pulsed power systems due to their advantages of high withstand voltage, fast establishing time and relatively high operating frequency. Multiple operation modes, which are induced by the different breakdown sequences at each stage, are found to affect the breakdown characteristics of the gas switch. Based on the theoretical analysis of the working principle, the classification of the operation mode and the factors determining the operation mode of the MSGS are proposed. Methods for investigating the output waveform for MSGS are established by simulating lumped parameters and studying the breakdown time sequence of individual stages. In comparison with the intended mode of operation, the disadvantages of the unintended modes of operation for MSGS, including error-breakdown and non-triggering mode, are revealed. For unintended modes, the distortion of the output waveform, which determines the efficiency of energy transmission through the switch and the increased delay time jitter, which determines the synchronization of the gas switch, are further investigated. The possibility of non-triggering and its mechanism on surface flashovers induced by drifting electrons are also analyzed. Based on this study, design principles and methods are proposed to ensure the intended operation of the MSGS.

Integral, Long Lifetime, Laser Diode Triggered Gas Switch Based on Light Initiated Multigate Switch

Integral, Long Lifetime, Laser Diode Triggered Gas Switch Based on Light Initiated Multigate Switch

A Compact UV-Illuminated Three-Electrode Field-Distortion Gas Switch With Sub-Nanosecond Jitter

A Compact UV-Illuminated Three-Electrode Field-Distortion Gas Switch With Sub-Nanosecond Jitter

Estimation Of Turkey's Carbon Dioxide Emission with Machine Learning

Carbon dioxide emissions are an important factor in the increase of greenhouse gases in the atmosphere and climate change. Controlling and reducing carbon dioxide emissions plays an important role in combating global warming and climate change. Various national and international efforts are being carried out to reduce greenhouse gas emissions and switch to sustainable energy sources. For this reason, estimating carbon dioxide emissions in the coming years is important for determining the measures to be taken. 
 In this study, Turkey's carbon dioxide emissions are successfully estimated using two different machine learning models. The success of the study was evaluated using three different statistical measures: R2, MSE and MAE. The R2 of decision trees was 89.4%, MSE was 0.013 and MAE was 0.011; the R2 of artificial neural networks was 92.7%, MSE was 0.009 and MAE was 0.006. When we compare the two models, it is seen that ANN is more successful than decision trees and predicts with less error.

Influence of Gap Distribution on Conduction Delay of Multigap Gas Switch

Influence of Gap Distribution on Conduction Delay of Multigap Gas Switch

A two-terminal fault location method for gas switch prefire in linear transformer driver.

Large-scale linear transformer drivers (LTDs) are composed of numerous high-power gas switches, and switch prefire is a frequent operational fault. To detect and locate the faulty switch accurately and efficiently, a two-terminal location method is proposed. A B-dot sensor is integrated on the gas switch's shell to collect the discharging signal. All the B-dot sensors are connected in parallel through cables of equal length. The fault position can be determined by the time delay of the signals at the two terminals. A diode is inserted between the B-dot sensor's coil and the cable core to ensure low-loss transmission of the signal. Two methods are applied in fault location, including time-of-arrival (TOA) and time reversal (TR). For the TOA method, an energy criterion and a phase criterion are applied and compared. The accuracy of the energy criterion is greatly influenced by the signal-to-noise ratio, while the phase criterion requires a reasonable estimate of the actual delay to account for the impact of phase periodicity. The TR method based on a precise simulation model is established, which demonstrates high precision in location. The TR method has been tested and validated on a single stage LTD module. Moreover, the location method for double switches prefire is discussed theoretically. The method proposed in this paper will be helpful to improve the efficiency of the commissioning, operation, and maintenance of the large-scale LTD devices.

Study on Triggering Failure Test Criterion and the Law of ‘Touch-Through’ Characteristics of Gas Switch Plasma Jet

Study on Triggering Failure Test Criterion and the Law of ‘Touch-Through’ Characteristics of Gas Switch Plasma Jet

Experimental investigation and theoretical analysis of the breakdown time delay and jitter of multi-gap gas switch gaps.

The gas gap of a multi-gap gas switch can be classified as trigger and self-breakdown gaps based on the breakdown condition. A two-gap gas switch consisting of a trigger gap and a self-breakdown gap is developed to independently study the breakdown characteristics of these two types of switch gaps. Trigger experiments for the switch are conducted under various trigger voltage rise rates and different working coefficients. The experimental results indicate that the trigger gap has significantly more jitter than the self-breakdown gap, and the overall performance of the gas switch is determined primarily by the trigger gap. A novel pre-ionization structure with disks is implemented into the two-gap gas switch, considerably decreasing the breakdown delay of the trigger gap and reducing the jitter to a quarter or even less compared to that without pre-ionization. A calculation model of the breakdown time delay for the trigger gap is provided based on the foundational development of the avalanche. The probability distribution of the time required for the initial electron generation is derived in the absence of pre-ionization. The calculated breakdown time delay agrees well with the experimental results in cases with and without pre-ionization under most trigger settings. The method and principle of calculating the breakdown time delay can analyze the collapse of a gas gap with different electrode configurations (quasi-uniform or uniform electrical fields) and various gas media under a nanosecond pulse voltage.

Study on discharge characteristics of six-gap gas switch with corona assisted triggering.

To improve the triggering characteristics of the gas switch used for linear transformer driver, a method of corona assisted triggering based on the pre-ionization in switch gaps is proposed and applied to a six-gap gas switch. The principle is demonstrated by electrostatic field analysis and verified by the experimental study on the discharge characteristics of the gas switch. The results indicate that when the gas pressure is 0.3 MPa, the self-breakdown voltage remains about ±80kV, and its dispersivity is lower than 3%. The effect of corona assisted triggering on the triggering characteristics increases with the higher permittivity of the inner shield. The positive trigger voltage of the switch with the proposed method can be reduced from 110 to 30kV at a charging voltage of ±80kV when the jitter is equal to that of the original switch. There are no pre-fire or late-fire when the switch operates continuously for 2000 shots.

Improved Marx Pulse Generator With Auxiliary Trigger Topology (2022)

Marx multi-stage circuits based on avalanche transistors are widely used in high-power nanosecond pulse applications. In response to the low reliability of the conventional Marx circuit, this paper analyzed the corresponding failure mechanism and discovered that the conduction modes were the main cause of failure. Based on this, a new topology is designed, by changing the conduction mode from "overvoltage switching-on" to "triggering switching-on". The simulation and measurement results show that the new structure has the advantages of high efficiency, stable operation, low output delay and short output pulse front. Meanwhile, to further improve the output efficiency,= a multiplexed stacking solution is designed based on the new structure, and the simulation results show that the output efficiency is up to 95%. The research in this paper can provide solutions for accurate and reliable synchronous triggering of key units such as gas switches in pulsed power systems, and also provide references for the design of high-efficiency nanosecond pulse generators.

Investigation of Delay Jitter of Avalanche GaAs PCSS for Triggering High-Voltage Gas Switch

The delay jitter characteristics of gallium arsenide (GaAs) photoconductive semiconductor switches (PCSSs) triggered in avalanche mode were experimentally investigated under dc bias. In the dark-state measurement, the PCSS was tested under a 40-kV bias voltage to verify its withstanding voltage and reliability. In the ON-state measurement, the delay jitter time of PCSS at different triggering positions was measured. The experimental results showed that the shortest delay jitter time was obtained when the laser was applied to the middle position of the cathode electrode. To evaluate the long-time stability, the delay-jitter time was recorded after continuous shots. It shows an ascending trend in delay jitter time with the increase in operating shots. The degeneration of the delay jitter time of the PCSS was mainly attributed to the device damage, including electrode ablation and filament current ablation, which was verified by the analysis of scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). Furthermore, a bipolar high-voltage gas switch integrated with PCSSs was successfully triggered by a low-energy fiber laser.

A novel method for multichannel discharge image diagnosis in gas switches based on multi-axis tomography techniques

The discharge channel is a crucial diagnostic tool for identifying the properties of gas switches. However, single-view images cannot easily be used to inherently understand the discharge channel characteristics of trigger electrodes. A reconstruction method of the discharge channel in gas switches is proposed based on a multi-axis tomography technique, which uses very few projections of optical images to reconstruct the location of a multichannel discharge in annular electrodes. In this paper, an algorithm named TVM-OSEM (total variation minimization ordered subsets expectation maximization) is proposed, which can effectively remove artifact noise to improve the reconstruction accuracy of discharge channels. The method is validated against simulations of a radiator with high-density-difference boundary. The calculated discharge channel distribution from one experiment is presented.

The Development of Solid-state Pulse Generator based on Marx Circuit with Chopping Switch

A solid-state pulse source is mainly formed by replacing the spark switch in a traditional pulse source with semiconductor switch device. Compared with conventional gas switch devices such as spark switches, semiconductor switch devices have the advantages of high work repetition frequency, long service life, small size, high efficiency, high reliability, easy control, and active shutdown. However, there are still problems, such as the solid-state switch being easily broken down by high voltage, the rising and falling edges of the pulse being slow, and the loss is enormous. In this paper, a solid-state pulse generator based on Marx with a chopping switch circuit is developed, which effectively solves the above problems. The pulse generator comprises DC power, a switching power circuit, a Marx circuit with a chopping switch, a serial port touch screen, and an optical fiber transmission circuit.