Pseudospark switch (PSS) is a high voltage and high current switching device operating in the low-pressure discharge regime with unique hollow cathode-anode electrode geometry. In this paper, the switching characterization with hydrogen gas at different loads (R L = 8.3 Ω & 2.7 Ω) have been presented for the multi-gap multi-aperture pseudospark switch (MGMA-PSS) for fast pulse power applications. Simulation analysis has been carried out to understand the role of the multi-aperture geometry for the different aperture sizes (2.4 mm & 3 mm). Switching characterization of the MGMA-PSS has been carried out at different operating conditions. The switching performance is observed with and without saturable inductor (SI). The SI is used to improve the switching behavior by reducing the commutation losses during the discharge process. Further, circuit analysis is also studied for the multi-gap arrangement of the discharge. This study would be very much useful for the optimization of the discharge characteristics for the design and development of high-power multi-aperture PSS for fast pulse power applications.
In the present research work simulation and experimental investigations have been carried out for discharge characterization of single to multi-gap pseudospark discharge-based plasma cathode electron (PD-PCE) source for the generation of high-density and energetic pulsed electron beam. The developed PD-PCE source has been operated with different gases (Ar, N2, He), applied voltages (5-35 kV), and electrode aperture sizes (2-6 mm). The proposed analysis has helped for the design and development of multi-gap (4-gap) PD-PCE sources having uniform sequence of electrode apertures (SEA) diameters (2 -4 mm) for pulsed electron beam generation. The pre-breakdown, hollow cathode and conductive phases have been analyzed and found their dependency on the operating and circuit parameters. The generation of high density $(\sim 3.0\times 10^{5} {\mathrm {A}}/{\mathrm {cm}}^{2}$) and up to 32 kV pulsed electron beams are governed by the penetrated dynamic equipotential lines in the 4-gap PD-PCE source having uniform electrodes aperture diameter of 2 mm. In addition, it also facilitates the generation of the high pulsed electron beam current of $\sim 1.5$ kA with the current density of $\sim 1.0 {\mathrm {x}} 10^{4} {\mathrm {A}}/{\mathrm {cm}}^{2}$ at $\sim 35$ kV applied voltage with the 4 mm electrode aperture. These studies would be very much beneficial for the generation of short pulsed electron beams for EUV/soft X-ray radiation and surface modification of materials.
Electromagnetic repulsive forming technology is a high-strain rate forming technology used for shaping of components made of metallic sheet, tube forming, joining operations, explosive welding, etc. A current pulse is passed through the tooling coil, generating a high-intensity magnetic field, which interacts with the induced currents in the electrically conductive workpiece, resulting in significant plastic deformation. The generated magnetic pressure, in this case, pushes the workpiece away from the coil. Electromagnetic attractive forming technology is another method to produce an attractive force on the workpiece using induced currents. However, this requires specialized pulsed power circuits and tooling systems to achieve the final objectives. This paper presents the design of a novel uniform pressure universal tooling coil that can be used for both repulsive and attractive forming of the workpiece without changing the pulsed power source and the tooling coil configurations. The designed tooling coil provides flexibility of operation, and the forming modes can be easily switched as per the process requirements. The paper focuses on the electromagnetic design of the tooling coil, and the performance of the tooling coil has been simulated in both configurations. The operating principle has been described in detail, and the results have been discussed in both the forming modes.
A Vector Inversion Generator (VIG) takes electrostatically stored energy and converts it into a fast-rising high-voltage pulse. VIGs have been created by winding a double layer of conductive foil and dielectric material on a cylindrical mandrel creating a spiral wound device. The author has built and tested a VIG in a novel geometry that exhibits the same Vector Inversion Generator principle as a spiral wound device. The proof of principle testing results of the novel geometry VIG are compared to those of a spiral wound VIG of approximately the same single-line conductor area, number of windings, and equivalent diameter. The comparison shows that the novel geometry VIG creates nearly the same output fast-rising high-voltage pulse as the spiral wound VIG and with the same level of efficiency. The novel geometry VIG shows promise for enabling the creation of VIG pulse generators in a more compact geometry with a lower overall device weight than the equivalent spiral wound VIG.
We are reporting on a capacitor charger with a rated peak voltage of 50kV. The charger is fed from a standard 208V, 3-phase AC utility outlet. The HV package, consisting of a high frequency transformer, HV rectifier and HV feedback voltage divider was provided by Stangenes Industries and is contained in a 19 inch, 5U rack mountable package. The primary of the transformer is driven by an H-bridge inverter. Inverter current control is achieved through a Digital Signal Controller (DSC) with a fast PWM controller and a programmable analog comparator. The DSC provides cycle-by-cycle peak current mode control as well as current loop stabilization through digital slope compensation. The charger is controlled by an Industrial controller with a touch screen interface. The touch screen interface involves multiple programmable and customizable screens. The controller monitors the output voltage of the load capacitor and closes the voltage loop. A back-up safety function limits the charge time should the voltage loop be broken or not work properly.
Parylene C coating is used to mitigate local electric field intensification in high-alkali BAS (Schott D263T) glass and low-alkali BAS glass (Schott AF32) with the aim of improving the dielectric breakdown characteristics. The breakdown events in these glasses were analyzed using a two-parameter Weibull probability distribution. Our findings demonstrate that the parylene C coating effectively mitigates the intensified electric field and reduced the risk of surface damage from thermal shock. Consequently, the weakest breakdown events are shifted to higher breakdown voltages and longer times, leading to a significant increase in the Weibull modulus. For anode-coated D263T glass, the Weibull modulus increases from 19.90 to 45.88 (a 130.55% enhancement), while for anode-coated AF32 glass, the increase is from 3.82 to 28.53 (a 646.86% enhancement), compared to uncoated glass. Although cathode-coated glass also demonstrates an improvement in the Weibull modulus, the enhancement is not as substantial as that observed in the anode-coated glass. Furthermore, we employ a finite element analysis model to simulate our experimental observations, aiming to enhance our understanding of the impact of polymer coatings on the dielectric breakdown of glasses with spatial and compositional fluctuations.
The introduction of nickel, manganese, cobalt-oxide (NMC) lithium-ion batteries in military systems allows for employment of new energy-and power demanding applications. However, such systems may imply high safety requirements as well as use during extreme conditions. This paper present a novel method using constant flux calorimetry to measure the thermal response of a single 21700-battery to estimate heat losses in the cell during discharging. Using a battery cycler, battery cells were discharged with repetitive high current pulses, with pulse width of 100 ms, a pulse repetition frequency at 1 Hz and current at 100 A for 2 minutes as well as with a constant current at 10 A for 2 minutes. These two discharge processes result in different amount of heat loss, were the losses during 100 A pulsing are around 15 times higher compared to that of the constant 10 A discharging. Despite this, Galvanostatic Electrochemical Impedance Spectroscopy (GEIS) measurements performed pre-and post-cycling, confirmed no significant performance degradation of the cell.
Temporally resolved emission spectroscopy capturing the light emission from 200 to 800 nm is utilized to assess the behavior of pulsed anode-initiated surface flashover in vacuum. The limiting failure mechanism at vacuum-insulator interfaces tends to be surface flashover since it occurs at field thresholds lower than bulk insulator breakdown or bridging plain vacuum gaps. Of particular interest are insulator geometries whose surface is angled to the electric field such that the electrons are pulled away from the surface. This often-dubbed “positive” surface geometry is known to outperform planar or negative angle geometries under most circumstances. This research examines a positive 45° insulator system subject to conditions that emulate those experienced in the insulator stacks of large-scale pulsed power machines, such as Sandia National Laboratory’s Z-machine: voltage risetimes in the tens of nanoseconds, pressures in the single microTorr, and peak electric fields of hundreds of kilovolts per centimeter at the anode triple junction. Cross-linked polystyrene (Rexolite) insulators were tested under these conditions and investigated with spatiotemporally resolved spectroscopy. Carbon ions are identified which originate from either the insulator itself or from adsorbed gases, as well as aluminum and magnesium ions from the metal electrodes. Simulated spectral lines of the carbon ions show agreement with the measured spectra for a Boltzmann temperature of 2.75 eV, while metal species require a reduction in temperature of at least 1 eV in order to match. These results lend some insight into the non-equilibrium nature of the early stages of anode-initiated flashover.
Pulsed power for controlled fusion applications can be the dominant portion of the total capital cost. With potential stored-energy requirements on the order of 100 MJ, the energy density of high-voltage capacitors (~50 kJ/m 3 ) can imply enormous laboratory facilities. For an actual power plant required to operate with billions of firings over thirty years, the energy density must be reduced (~3.6 kJ/m 3 ), increasing the system size (and cost) further. Energy storage in high pressure (~25 kpsi) gas offers much higher energy densities (~255 MJ/m 3 ) and can supply a pulsed power system completely analogous to an electrical one, but much smaller. Such an approach had been envisioned for controlled fusion based on stabilized imploding liner compression of plasma, but can also extend to repetitive manipulation of magnetic flux for other pulsed power needs.
Thermionic cathodes have been shown to be a reliable source of electron emission to produce and deliver electron beams of various voltages and currents. One drawback of using thermionic cathodes is the possibility of electrons emitting off the side of the cathode due to high enough electric field values near the cathode edge. These extra electrons induce nonlinearities in phase space which contribute to an increase in beam emittance. In this work we highlight the results of trade-space studies that show by tuning cathode-shroud parameters, we can mitigate these effects on the phase space and generate electron beams whose emittance with side emission electrons is comparable to a beam where side emission is not present.
A relativistic magnetron with a novel diffraction output has been analyzed with 3D particle-in-cell simulations. Using a six-cavity relativistic magnetron with a cylindrical cathode, the generated microwaves are propagated through a diffraction output tapered with four radially opposite cavities, to produce a TE11-mode in a cylindrical waveguide at the output. The performance has been evaluated for different input coaxial line radii, voltages ranging from 185 kV to 330 kV in the anode-cathode gap and applied magnetic fields generated by a Helmholtz pair from 0.26 T to 0.32 T. Results show successful and efficient TE11 operation. An efficiency maximum of 46% is found for an axial magnetic field of 0.32 T and a voltage of 270 kV, generating an output microwave power of 0.36 GW at 2.57 GHz. Also, the electron leakage current is found to be 10% of the total current. These results motivate continued interest in the relativistic magnetron with diffraction output for high power microwave applications.
High-voltage pulses with a stepwise arbitrary waveform can be generated by switching the stages of a pulse generator individually according to a pre-defined switching sequence for each stage. Thereby, the individual stage voltages depend on the initial charging voltage and the discharge rates of the stage capacitors, which vary with the on-time of the stage switches and the related discharge currents. While a parallel configuration of the stage capacitors during charging results in the stage capacitors to be charged to an almost equal voltage at the beginning of the pulse, the individual control of the charging voltage at each stage allows for a more precise adaptation of the voltage steps and, hence, the generator’s output voltage. For initial tests, a four-stage pulse generator featuring an individual power supply per stage has been set up. The energy is transferred to the stages via transformers. Its primary windings are connected in series configuration to form a loop, which is powered by an AC current source at a frequency of approximately 100 kHz. The energy flow to the stages is controlled by means of a shunt regulator. Each stage is equipped with a pulse capacitor of 55 μF, which can be charged individually up to a voltage of 800 V per stage. The stages are designed to generate a pulse current of up to 90 A. Thereby, a pulse generated by a single stage connected to a resistive load has a rise time of less than 5 ns. The pulse switch of each stage features three SiC-MOSFETs in parallel configuration operated under gate-boosting conditions in order to achieve a fast rise time. The stages are controlled via a fiber-optic link. In the contribution selected design details and measurement results from tests of generating pulses having a rectangular voltage shape will be presented.
One of the major remaining technical hurdles facing tokamaks, a leading architecture for fusion systems, is that plasma disruptions can result in the generation of high current beams of relativistic electrons (10s of MeV). These beams are called Runaway Electrons (RE). In advanced fusion machines, Runaway Electrons can cause severe damage to plasma-facing surfaces of a tokamak structure. This catastrophic destruction includes melt damage, coolant leaks, and loss of vacuum.High field tokamaks, which will be required for commercial fusion power, will be even more susceptible to damage from RE than present-day systems such as ITER. Even if these events occur rarely, they could hamper fusion machines from reaching commercial viability. To prevent these events from damaging tokamaks, a non-axisymmetric coil can be excited to disrupt the magnetic field and prohibit formation of such relativistic electron beams. Diversified Technologies, Inc. (DTI) is working under a Small Business Innovative Research (SBIR) grant from the Department of Energy 1 (DOE) to develop a fast-acting high current switch and vacuum feedthrough controlling a magnetic coil. When passively switched ON, this will disrupt formation of the relativistic beams, and prevent damage to the plasma facing surfaces. As part of the switch design, protective circuits are integrated to ensure proper switch operation.The full-scale switch and feedthrough will be installed in a working fusion device for full-scale tests. This effort is in collaboration with MIT and General Atomics (GA) for future installation on the GA fusion device (DIII-D) as a prototype.
U.S. Navy ships need more electric power for increased capability, automation, mobility, lethality, and they need increased operating efficiency for reduced fuel costs. This is motivating the adoption of Direct Current power distribution systems. The voltage range is from 1 kV to 12 kV or greater (LVDC to MVDC), and the steady state current range is up to 5 kA. DC circuit breakers operate faster than AC breakers since they circumvent the current zero-crossing requirement of AC breakers. Protective DC switchgear is a key element in a DC power distribution system that provides electric power reliably and cost-effectively, utilizing more efficient, high-power sources, energy storage, and transmission. For over 25 years, Diversified Technologies Inc (DTI) has been designing and building high-voltage DC circuit breakers capable of multi-kA switching at voltages up to and greater than 100 kV. DTI has shipped and qualified for military applications hundreds of systems. These switches are well-suited for shipboard DC circuit breaker applications. This paper describes on-going hybrid and solid state circuit breaker development at DTI.
Recent years have seen numerous studies into how applying pulsed high electric fields (PEF) to living organisms induces various stress reactions. Plants produce glucose through photosynthesis and use this as a source of energy for living, yet there are few studies on the photosynthetic response characteristics when PEF is applied to growing plants. In this study, the photosynthetic response when electric fields of 10 to 100 V/mm were applied to light and dark-acclimated leaves of lettuce was measured by combined gas exchange and chlorophyll fluorescence, and the exposure time was kept constant at 500 s. The responses to PEF with regard to the photosynthetic parameters of electron transfer rate (ETR), non-photochemical quenching (NPQ), photosynthetic rate (A), and transpiration rate (E) were recorded during the experiment. Results showed that PEF can cause both the activation and deactivation of photosynthetic activity in lettuce, that there is an optimum value for activation, and that the application of excessive energy leads to inactivation. This study also found that stomata on both active and deactivated lettuce had been open to a greater extent than lettuce to which PEF had not been applied. All the results of statistical significance in this study were p < 0.05 and p < 0.01.
The WARP Reactor Concept promises orders of magnitude increase of intense ion beam energies and respective radiation yields at a fraction of the size and cost over existing z-pinch class accelerators allowing the economically viable study of new Relativistic High Energy Density Physics regimes for probing the intersection between General Relativity and Quantum Field Theory along with game-changing direct applications from reprated Magnetized Liner Inertial Fusion devices for energy production and advanced propulsion to multi-pulse compact flash x-ray/neutron radiography sources for assessing our Nation’s aging nuclear weapons stockpile. A brief overview of the WARP Reactor Concept is provided here with more in-depth treatment with additional figures and tables provided in the companion PPC2023 conference presentation.
This paper aims to study the impact of slew rate on partial discharge (PD) characteristics of BOPP film under nanosecond pulse voltage. To achieve this, experiments were conducted to detect partial discharges in BOPP films subjected to high rise rate (slew rate) nanosecond pulse voltages. The study found that the repetitive partial discharge inception voltage (RPDIV) initially increased and then reached a stable level as the rise time increased. Additionally, the PD amplitude and the number of RSD increased with higher slew rates, while the PD time-lag decreased gradually. Similarly, for FSD, the PD amplitude, PD numbers, and PD time-lag all increased as the slew rate increased. Furthermore, the study observed that when the slew rate was below 50 V/ns, the PD characteristics exhibited rapid changes with increasing slew rate. However, when the slew rate exceeded 50 V/ns, the PD characteristics showed slower variations as the slew rate increased. These presented results contribute to a better understanding of the behavior of PD in film capacitors under nanosecond pulse voltage with high slew rates. They also provide valuable guidance for evaluating the insulation performance of film capacitors.
Recently, a nanosecond pulse power supply capable of generating a pulse voltage with a pulse width of 5 ns and a voltage rise rate of 7.5 kV/ns has been developed and demonstrated to have higher treatment efficiency than general pulsed discharge methods in applications such as ozone generation and exhaust gas treatment using it. However, there is still room to clarify the characteristics of nanosecond pulsed discharge plasma, and clarification of these characteristics will lead to higher treatment efficiency. Therefore, in this study, we focus on the propagation speed of primary streamers generated by nanosecond pulsed discharges, and by using a quadruple emICCD camera system, we observe the propagation speed of primary streamers to evaluate the propagation characteristics of nanosecond pulse streamers.
The recovery of carbon fiber (CF) from wasted carbon fiber reinforced plastic (CFRP) composites and the reuse of CF have been also required in the resource recycling. The previous study of recovery CF using the torrefaction reported that 15-50 % reduction in tensile strength of recovered CF compared to virgin CF. It is necessary to develop the recovery technology of CF from CFRP without reducing tensile strength of recovered CF. In this study, we evaluate the applicability of pulsed discharge with instantaneous high energy releases as a novel approach, which is already known to be effective in separating cathode particles from aluminum foil of lithium-ion batteries (LiBs) based on our previous investigation. The separation of cathode particles was caused in the interface between the foil and particles by deactivating adhesive strength of binder which connected these due to the Joule heating of the foil generated by the current of discharge. The object of this study is to applicate pulsed discharge to recover CF without attaching polymer matrix from laminated CFRP with delaminating CFRP layers by loading discharge horizontally. The tested sample sizes of laminated CFRP were 100 mm length, 30 mm width and 8 mm thickness. Two electrodes of pulsed discharge were set on the surface of sample, and the electrode gap was 50 mm. The pulsed discharge with conditions of capacitor capacity of 80 μF, charging voltage of 10 kV and charging energy in the capacitor of 4000 J was performed in the water. The CFRP layer was peeled, and fibers about 20 mm length were also recovered by the discharge. The scanning electron microscope (SEM) images for recovered fibers indicated that fibers were without the adhesion of matrix resin. It was assumed that the separation mechanism of resin from CFRP was that the insulation breakdown in resin was caused by the discharge, and the resin was removed by the plasmatization with high temperature, resulting in the recovery of CF. It is possible to consider that the volume expansion of resin induced by the plasmatization also caused the peeling of CFRP layer. The tensile strength of recovered CF was found to be 5.0 GPa by the single fiber tensile test and was 21 % less than that of the virgin one. These results indicated that pulsed discharge is effective in the recovery of CF from the laminated CFRP with the less tensile strength reduction of recovered CF.
The purpose of this study is to quantitatively evaluate the shockwave generated during the rapid volume expansion of thin aluminum wire by applying pulsed power. Conventional building demolition work involves the use of dynamite and excavators, which are noisy and labor intensive. Another problem is the difficulty of moving heavy equipment in urban and residential areas. To solve these problems, we developed a new method that applies pulsed power to thin aluminum wires installed at demolition points in advance and utilizes the shockwaves generated when the aluminum wires are exploded. In order to obtain the highest shockwave pressure during aluminum wire explosion, we investigated the dependence of the applied voltage, wire diameter, current rise time, wire material, wire shape, and number of wires. The voltage and current waveforms were measured with an oscilloscope, and the shockwave generated by the wire explosion was observed using Schlieren method with a high-speed camera. As a result, what emerges from the wire explosion is a shockwave and an expansion wave of evaporated gas after the explosion. Shockwave was investigated in terms of average velocity and pressure. For the expansion wave, the arrival distance was investigated. It was found that the highest values for the shock force and expansion wave were obtained when the number of fine wires was increased, and their volume was large.
