Recently, the new tendency in launch systems is moving toward electric-driven or electromagnetic (EM) launches, converting EM energy to kinetic energy. However, for efficient operation, these systems require high electric current pulses, which makes the design of their power supply challenging. To solve this problem, two classical solutions are used. The first, known as “XRAM,” is based on charging several coils in series and then discharging them in parallel to multiply the delivered current. The second technique is known as a “meat grinder” (MG), in which the energy stored in two tightly coupled coils is abruptly transferred to one of them with the lowest number of turns. It results in a sudden current amplification. This article discusses a new and improved architecture that combines these two techniques to increase the amplification ratio while minimizing the constraints on the primary power switch. A mathematical model of the system is developed to analyze all the operating phases of the generator. This model is validated and confirmed by a series of practical tests made on an experimental prototype.

When a near-space hypersonic vehicle flies at a velocity of several Machs, a plasma sheath is created on its surface. The plasma sheath is a complex electromagnetic (EM) medium composed of many charged particles, producing a series of EM effects on EM waves. In this article, based on the numerical calculation results of the plasma sheath flow field at typical altitudes, the spatial distribution characteristics of the reflection intensity of the typical reference area on the vehicle surface are solved. The EM shielding effect of the plasma-sheath-covered target is revealed by the incident depth and the maximum reflection position of the EM wave in the plasma. By analyzing the influence of different flight altitudes and carrier frequencies on the reflection characteristics of each typical vehicle area, the variation law of the EM shielding effect of the plasma-sheath-covered target is obtained. The research results reveal the EM shielding mechanism of plasma sheath and provide a theoretical basis for radar detection and radar cross Section (RCS) measurement of the plasma-sheath-covered target.

A silicon carbide (SiC) Schottky diode detector is employed to monitor the ion streams emitted from laser-generated plasmas and to obtain information on their kinetic energy using time-of-flight (TOF) measurements. The laser operates with nanosecond (ns) pulses, in the IR region at 1064-nm wavelength, uses single pulses with 200-mJ energy, and an intensity of about $10^{10}$ W/cm2. Plasmas are produced in a high vacuum by irradiation different targets as polymers, ceramics, and metals. The non equilibrium plasma, back emitted orthogonally to the target surface, accelerates ions at about 110 eV per charge state and has a temperature within 70 and 100 eV growing with the atomic number of the laser irradiated target. In this article, an optimization of ion detection is checked for SiC detectors through the TOF spectra, permitting the ion recognition and angular emission. A comparison with classical ion collectors (ICs) is also presented and discussed.

Modeling and simulation of the HERMES-III extended magnetically insulated transmission line (MITL) terminated by a diode with an annular cathode and a planar anode was performed with an electromagnetic particle-in-cell code, EMPIRE-PIC. Self-limited MITL theory was developed and implemented in order to model select shots in EMPIRE by allowing one to transform an experimental current trace into a voltage waveform that is input into EMPIRE. Simulating shots 11132, 11133, 11134, 11135, 11136, and 11146 in EMPIRE shows good agreement with experimental current traces at several locations along the MITL. New calibrations for the anode current shunts are proposed based on low-power shots fired into a short-circuited diode configuration (short-shots). The new calibrations show improved agreement with simulation results.

In this study, we investigated the influence of the electrode structure on ion beam extraction in a cold-cathode ion source. Numerical simulations were performed for three typical structures of cold-cathode ion sources with different cathode and anode geometries using in- house 2-D ion ray-tracing code. We found that the potential structure inside the plasma source, which is greatly influenced by the electrode structure, plays a significant role in determining the amount and divergence of the extracted ion beam. The electrode structure influences the potential structure inside the plasma source and forms a radial electric field between the sheath edge and the extraction aperture. The radial electric field guides the ion beam to focus or diverge in this region, thus changing the characteristics of the ion beam extracted from the aperture. The simulation results reveal that the ion source with the cylindrical anode geometry extracts a higher current than those with other geometries due to its potential structure, which focuses the ion beam more efficiently. The simulation results are consistent with those of our experiments with a small-sized cold-cathode ion source.

Closing switches based on series-connected shock ionization dynistors (SIDs) with an operating voltage of 16 and 24 kV are described. Various schemes for constructing these switches are considered. It is shown that experimental SID blocks based on series-connected chips with a diameter of 24 mm at a repetition rate of 500 Hz are capable of switching sub-microsecond current pulses with an amplitude of $\sim $ 4 kA, and in the single-pulse mode, they are capable of switching current pulses with an amplitude of $\sim $ 17 kA and a rise rate of $\sim $ 50 A/ns. The prospects for increasing the switched power of the developed high-voltage SID switches are determined.

This article presents an advanced 3-D electromagnetic co-simulation approach developed using the CST software to evaluate the characteristics of a bipolar subnanosecond pulse forming system for application in the biomedical and defense domains. To the best of the authors’ knowledge, the simulation technique presented in this article, which integrates transient switching devices in the 3-D electromagnetic model of the bipolar subnanosecond pulse forming system, was not presented previously in the open literature. The design of the bipolar subnanosecond pulse forming system is based on a thorough analytical calculation with predictions verified using the 3-D numerical modeling to generate a voltage of up to 500 kV peak-to-peak amplitude with a duration of around 1.8 ns when connected to a $50~\Omega $ load. A good agreement between the experimental results and the CST predictions was obtained, providing the correctness of the proposed modeling technique. Future plans involve connecting the bipolar subnanosecond pulse forming system to an ultra-wideband (UWB) antenna.

In this article, we have employed an atmospheric pressure plasma jet (APPJ) system to produce graphene layers on polymeric substrates for large-area applications. Herein, the graphene layers are grown on four different polymers polyamide6 (PA-6), high-density polyethylene (HDPE), polypropylene (PP), and polyurethane (PU) using 200 W of 13.56-MHz RF power supply-induced APPJ with argon as primary gas in an open atmosphere. The formation of the graphene layers has been confirmed by Raman spectroscopy, X-ray diffraction (XRD), and field emission electron microscopy (FESEM). The optical emission spectra (OES) of the plasma plume have been taken to analyze the presence of active species. To ensure the thermal integrity of the polymers, thermal gravimetric analysis (TGA) has been done after the plasma treatment. Furthermore, the prepared samples have been tested to verify various properties of graphene, like hydrophobicity, electrical conductivity, bacteria detection, and antimicrobial properties. The hydrophobic nature of graphene has been tested by measuring the contact angle. The electrical conductivity has been measured using the four-probe method to find out the applicability of the graphene-coated substrates for flexible electronic applications. The electrochemical three-probe-based $I$ – $V$ characterization has been done for E. coli bacteria detection, and the antimicrobial activity of the prepared samples has also been analyzed.

Pulsed gas discharge has been studied using a pulsed power generator with a bipolar solid-state linear transformer driver (SSLTD) scheme. Taking advantage of the output flexibility of the bipolar SSLTD, we have studied the residual charges phenomenon by the coaxial discharge load. The experiment result shows that for two consecutive positive pulses discharge, the current of the second positive pulse is usually lower than that of the first pulse for the same voltage amplitude. However, a middle negative pulse applied between the first and second pulse can increase the current of the second positive pulse. An explanation for this phenomenon has been explored using a 1-D model that considers the effect of residual charge left by the previous pulse discharge. According to the explanation of our 1-D discharge model, this phenomenon may be caused by the residual charge distorting the discharge electric field strength. The findings obtained by this article will help us understand the fundamental characteristics of pulsed atmospheric pressure gas discharge.

In this article, a strongly coupled one-component plasma (OCP), where ions interact with a background of weakly coupled electrons, is considered. The thermodynamic properties of this plasma were studied on the basis of three types of interaction potentials. The first potential with ionic core obtained from $ab initio$ simulations takes into account the effects of the bound electrons, the second is the well-known Yukawa potential, and the third is the effective potential derived by the method of dielectric response function taking into account electron screening and quantum-mechanical diffraction effect of electrons. The radial distribution functions (RDFs) were calculated for the first potential using molecular dynamics (MD) simulations and were additionally compared with the RDFs obtained for all three potentials by solving the integral Ornstein–Zernike equation in the hypernetted chain (HNC) approximation and show that the use of the effective potential is not applicable at warm dense matter (WDM) conditions, when the ion core is significant.

The particle-in-cell Monte Carlo collision (PIC-MCC) model is an essential way to investigate the kinetic behaviors of low-temperature plasmas, but usually, it is hugely time consuming in simulating atmospheric radio frequency (RF) plasmas. In this study, a deep neural network (DNN) with multiple hidden layers is developed to predict the kinetic discharge characteristics of atmospheric RF plasmas. The results obtained from the PIC-MCC model are used as the training dataset for the DNN, and the well-trained DNN is able to efficiently yield various kinetic behaviors of atmospheric RF discharges with very high precision. The validation of the results predicted by the DNN algorithm is performed by comparing them with the simulation results directly from the PIC-MCC model. Compared with the time-consuming PIC-MCC simulations, the well-trained DNN takes only 0.01 s to yield the essential kinetic characteristics of atmospheric RF discharges, which saves seven orders of magnitude of computation time compared with the traditional PIC-MCC simulation. The predicted data show that the discharge current of atmospheric RF discharges increases monotonically with the driving frequency at a given applied voltage, and as the driving frequency increases, the electric field in the sheath region is strongly enhanced with the sheath region shrinks and the bulk plasma region expanding. Additionally, the electron energy distribution function (EEDF) can be accurately predicted by DNN; moreover, as the driving frequency increases, the low-energy electrons can be transformed into medium-energy electrons, leading to a transition of the EEDF from a three-temperature distribution to a Maxwellian distribution from the DNN prediction. The study indicates that the well-trained DNN is a promising tool for plasma simulation with very high efficiency and accuracy compared with the PIC-MCC model with huge computational costs, which could provide enough kinetic results to further understand the discharge behaviors in atmospheric RF discharges.

An advanced breeding blanket for excellent tritium breeding performance shall be designed to realize the operations of Chinese Fusion Engineering Testing Reactor (CFETR) at steady-state burning tritium fuel in the core plasma for fusion reactions. Tritium release from blanket interior effectively requires a temperature range above than 400 °C. This indicates that the blanket temperature field distribution and its evolution are related to the online tritium breeding ratio (TBR) assessment. In this article, water-cooled ceramic blanket (WCCB) models are built to perform the TBR estimation and the temperature field simulations. It is confirmed that the temperature field affects the TBR variation, which is linked to the blanket cooling pipes (CPs) layout. In addition, the effective volume fraction of tritium release of the blanket model is defined to evaluate the breeding regional proportion whose temperature is higher than 400 °C. The effective volume fraction of tritium release is analyzed for the inlet coolant temperature ranging from 0.6 to 5.0 m/s by an Eulerian-Eulerian two-phase numerical simulation method. The outer surface temperature of CPs can be raised toward 400 °C when inlet velocity is 1.1 m/s. This is a vital approach to reduce the deep temperature gradient in blanket interior, which is beneficial to the tritium release sufficiently. The estimation of critical heat flux (CHF) of first wall (FW) indicates that boiling crisis will not take place in FW. This work is helpful to the engineering design of fusion blanket considering the tritium self-sufficiency in the road toward fusion reactor.

One of the major components of commercial plasma display panel (PDP) cells is the magnesium oxide (MgO) protective layer. In order to obtain both lower discharge breakdown voltage and higher energy efficiency in the cells, other alkaline Earth metal oxides have been extensively studied as alternatives to MgO. Another important factor in the life-extending of PDP is resistance to ion sputtering. In this article, the Monte Carlo simulation program Stopping and Range of Ions in Matter (SRIM)-2013 was applied to study the behavior of the sputtering yield, vacancies/ions, backscattered ions, ion range, lateral and radial projection, energy loss due to ionization, vacancies, and phonons, of MgO, calcium oxide (CaO), SrO, and barium oxide (BaO) as a function of incident angle for Ne $^{+}$ and Xe $^{+}$ ion beam. It is discovered that CaO, SrO, and BaO protective layers increase the number of backscattered ions from surfaces when they are hit by noble gas ions. They resist sputtering and vacancies better than the MgO protective layer.

A double sheath characteristics and virtual cathode formation in a plasma containing $q$ -nonextensive distributed electrons, thermally emitted or secondary emitted electrons from the cathode wall, and ions are studied numerically. The distribution of primary (plasma) electrons is taken to be nonextensive, as per Tsallis statistics. The electric field at the cathode, the ratio of ion to electron current density and the velocity of ions are evaluated and the results are compared with the case of electrons having Boltzmann distribution. The variation of the electric potential, space charge density, and sheath thickness are analyzed for the cases of different nonextensivity $q$ . The electric field at the cathode becomes zero at a lower value of electron beam current density, and hence the formation of the virtual cathode takes place earlier for the case of super-extensive distributed electrons as compared to that of the Boltzmann-distributed electrons. For super extensively distributed electrons, the electric potential drops slowly to a minimum, the velocity of positive ions increases inside the sheath, and an increase in the sheath thickness is observed.

When the reentry target passes through the earth’s atmosphere, its surface is covered with a layer of plasma sheath. In the process of radar detection of the reentry target, the echo signal will couple with multi-Doppler frequency components and form multiple mismatch effects with matched filter, which will produce false targets on the 1-D range profile. Meanwhile, the excessive speed of the reentry target will lead to the phenomenon of migration through range cells (MTRCs), which will further affect the detection and recognition of the target. This article proposes an improved frequency-domain compensation method that aims at false target and cross-range unit migration. By constructing the intrapulse Doppler frequency and interpulse Doppler frequency compensation functions, the multiperiod echo signal is processed to eliminate the MTRC phenomenon and improve the energy gain of the real target. Finally, the feasibility of the proposed algorithm is verified by simulation, which lays a theoretical foundation for the effective detection and reliable tracking of plasma-sheath-covered targets.

With the rapid development of multiterminal high-voltage direct current (HVdc) transmission systems, the research and development of high-speed and stable high-voltage dc circuit breakers have received attention. Among them, mechanical dc circuit breakers based on manual zero-crossing dc breaking technology have been applied in practical projects, owing to their small size, low on-state loss, and low price. However, this method adds a high-frequency current, which deteriorates the magnetic field between the poles of the interrupter when the arc is broken. Therefore, the development of HVdc circuit breakers that maintain high peak magnetic fields and low residual magnetic fields at high frequencies has become the key to the development of multiterminal HVdc transmission. To solve this problem, this article proposes a new interrupter for a vacuum dc circuit breaker based on artificial zero-crossing technology and studies its key characteristics, such as temperature rise, electromagnetic field, and arc column plasma distribution characteristics. The results reveal that the new interrupter proposed in this article has a low-temperature rise, uniformly distributed electric field, high peak value and low remanence of the longitudinal magnetic field, and uniformly distributed plasma in the arc column, and exhibits arc diffusion. Its ability to cope with high-frequency current is significantly higher than that of the traditional cup-shaped axial magnetic field (AMF) contact system interrupter, which is conducive to the high-speed and stable breaking of the interrupter.

Naval Surface Warfare Center Dahlgren Division (NSWCDD) has been exploring methods of maximizing coilgun electrical-to-kinetic energy transfer efficiency by optimizing the geometries of wire-wound drive coils and armatures. Such optimization permits a reduction in the number of stages for a multistage coilgun, thus decreasing its design complexity and power requirements. NSWCDD applied optimal design trends to the coilgun geometry and its energy storage configuration to build a single stage coilgun capable of launching a 447-g projectile to 144 mph, resulting in an efficiency of 14.47%. To date, this is the highest experimentally achieved efficiency of a single stage coilgun without the use of cooling or initial armature velocity. The efficiency may be determined by the drive coil current measurements with and without the armature, as an alternative to knowing the speed and mass of the armature.

A self-consistent, nonlinear analysis of the three-stage clustered-cavity gyroklystron amplifier has been developed. The investigation has been applied to the previously reported 32.3-GHz, second harmonic, three-cavity conventional gyroklystron amplifier operating at the TE02 mode for its performance enhancement in terms of bandwidth. Using the clustered-cavity analysis, a peak RF output of $\sim $ 310 kW, electronic efficiency $\sim $ 23%, and $\sim $ 27-dB gain have been obtained at desired 32.3-GHz frequency. The clustered-cavity device bandwidth has been obtained as $\sim $ 59.5 MHz, which is significantly much higher than the conventional-cavity case, i.e., $\sim $ 36 MHz. It is observed from the analytical results that the clustered-cavity approach widens the bandwidth with a slight increase in the device gain and efficiency. Furthermore, the effect of stagger-tuning in the clustered cavities on the device performance has also been explained in detail. The results confirmed that the increase in the stagger-tuning parameter to 0.5 further increases the device bandwidth to 103 MHz but with a considerable decrease in the gain parameter. Hence, there should be a tradeoff between the gain and bandwidth in terms of the stagger-tuning parameter. The analytical results obtained are verified further by carrying out the particle in cell (PIC) simulation of the designed gyroklystron amplifier using the 3-D PIC simulation tool CST Particle Studio for different values of stagger-tuning parameters. The simulated results obtained agree with the analytical results within 10%.

This article presents a compact high-voltage pulse modulator used for a 50-MW $X$ -band pulsed klystron (11.4 GHz) at Shanghai Advanced Research Institute, Chinese Academy of Sciences (SARI, CAS). The pulse modulator includes a ten-section pulse-forming network (PFN), protection circuits, a thyratron module, and a pulse transformer. To reduce the volume of the pulse modulator and maintain the system stability, an oil-immersed tank is proposed to insulate the main electronic components, which leads to a volume reduction of 65%. The modulator is designed with a peak pulse voltage of 427 kV, a peak pulse current of 304 A, a repetition rate of 50 Hz, and a flat-top pulsewidth of $1.3 \mu \text{s}$ . The circuit schematic is provided, while the design criteria of the main components and mechanical structure are discussed. The experimental results and measurements show the design and hardware to be capable of fulfilling the requirements.

Corona discharge under airflow is extensively researched due to its wide applications in the fields of electrostatic precipitator, flow control, thermal management, and so on. The adjustment of discharge characteristics has been an important research topic in recent years. In this article, a magnetic field is applied as a method to adjust the characteristics of corona discharge under airflow. The experimental result illustrates that the intensity and direction of the magnetic field would influence the turning point of the discharge state under airflow, and the corresponding discharge image and Trichel pulse characteristics, such as amplitude and frequency, would also be changed. The physical mechanism for this phenomenon is analyzed by considering the magnetic force of the corona discharge. With increasing magnetic field intensity, the pressure in the discharge space would change and the airflow state and the discharge process, as the ionization process and the attachment process, would be influenced. The overall characteristics of discharge under airflow would be adjusted by the magnetic field. The results illustrated that the magnetic field is possibly utilized to improve the application of corona discharge under airflow.