Plasma Science and Technology

Explicit structure-preserving geometric particle-in-cell (PIC) algorithm in curvilinear orthogonal coordinate systems is developed. The work reported represents a further development of the structure-preserving geometric PIC algorithm achieving the goal of practical applications in magnetic fusion research. The algorithm is constructed by discretizing the field theory for the system of charged particles and electromagnetic field using Whitney forms, discrete exterior calculus, and explicit non-canonical symplectic integration. In addition to the truncated infinitely dimensional symplectic structure, the algorithm preserves exactly many important physical symmetries and conservation laws, such as local energy conservation, gauge symmetry and the corresponding local charge conservation. As a result, the algorithm possesses the long-term accuracy and fidelity required for first-principles-based simulations of the multiscale tokamak physics. The algorithm has been implemented in the SymPIC code, which is designed for high-efficiency massively-parallel PIC simulations in modern clusters. The code has been applied to carry out whole-device 6D kinetic simulation studies of tokamak physics. A self-consistent kinetic steady state for fusion plasma in the tokamak geometry is numerically found with a predominately diagonal and anisotropic pressure tensor. The state also admits a steady-state sub-sonic ion flow in the range of 10 km s⁻¹, agreeing with experimental observations and analytical calculations Kinetic ballooning instability in the self-consistent kinetic steady state is simulated. It is shown that high-n ballooning modes have larger growth rates than low-n global modes, and in the nonlinear phase the modes saturate approximately in 5 ion transit times at the 2% level by the E × B flow generated by the instability. These results are consistent with early and recent electromagnetic gyrokinetic simulations.

An impurity powder dropper was installed in the 21st campaign of the Large Helical Device experiment (Oct. 2019–Feb. 2020) under a collaboration between the National Institute for Fusion Science and the Princeton Plasma Physics Laboratory for the purposes of real-time wall conditioning and edge plasma control. In order to assess the effective injection of the impurity powders, spectroscopic diagnostics were applied to observe line emission from the injected impurity. Thus, extreme-ultraviolet (EUV) and vacuum-ultraviolet (VUV) emission spectra were analyzed to summarize observable impurity lines with B and BN powder injection. Emission lines released from B and N ions were identified in the EUV wavelength range of 5–300 Å measured using two grazing incidence flat-field EUV spectrometers and in the VUV wavelength range of 300–2400 Å measured using three normal incidence 20 cm VUV spectrometers. BI–BV and NIII–NVII emission lines were identified in the discharges with the B and BN powder injection, respectively. Useful B and N emission lines which have large intensities and are isolated from other lines were successfully identified as follows: BI (1825.89, 1826.40) Å (blended), BII 1362.46 Å, BIII (677.00, 677.14, 677.16) Å (blended), BIV 60.31 Å, BV 48.59 Å, NIII (989.79, 991.51, 991.58) Å (blended), NIV 765.15 Å, NV (209.27, 209.31) Å (blended), NVI 1896.80 Å, and NVII 24.78 Å. Applications of the line identifications to the advanced spectroscopic diagnostics were demonstrated, such as the vertical profile measurements for the BV and NVII lines using a space-resolved EUV spectrometer and the ion temperature measurement for the BII line using a normal incidence 3 m VUV spectrometer.

The physics of electrodeless electric thrusters that use directed plasma to propel spacecraft without employing electrodes subject to plasma erosion is reviewed. Electrodeless plasma thrusters are potentially more durable than presently deployed thrusters that use electrodes such as gridded ion, Hall thrusters, arcjets and resistojets. Like other plasma thrusters, electrodeless thrusters have the advantage of reduced fuel mass compared to chemical thrusters that produce the same thrust. The status of electrodeless plasma thrusters that could be used in communications satellites and in spacecraft for interplanetary missions is examined. Electrodeless thrusters under development or planned for deployment include devices that use a rotating magnetic field; devices that use a rotating electric field; pulsed inductive devices that exploit the Lorentz force on an induced current loop in a plasma; devices that use radiofrequency fields to heat plasmas and have magnetic nozzles to accelerate the hot plasma and other devices that exploit the Lorentz force. Using metrics of specific impulse and thrust efficiency, we find that the most promising designs are those that use Lorentz forces directly to expel plasma and those that use magnetic nozzles to accelerate plasma.

The application and development of pulsed plasma thrusters (PPTs) in recent years are reviewed in this paper. The advantages of PPTs are discussed. The schematics, propulsion performance parameters and key physical processes of PPTs are described. Some representative PPT products and flight systems developed in recent years are presented to show the performance of the PPT. Studies about how electrode structures, discharge circuits, propellant materials, energy discharge method, propellant feed method, ignition method and number of thruster heads influence the PPT performance are presented and analyzed. The ignitor design method, ignition process and propellant carbonization are introduced to discuss the reliability and lifetime issues in PPTs. The modeling methods of the discharge circuit, as well as ablation, ionization and acceleration in PPTs are presented. Finally, the application of PPTs in the future is analyzed and some suggestions for PPT development are proposed.

The dual cylindrical inductively coupled plasma source, compared to the conventional structure of inductively coupled plasma source, can significantly improve the uniformity of plasma. It has an enhanced potential for application in processes, such as etching and ashing. A uniform plasma can be obtained by allowing the remote plasma from the upper chamber modulate the main plasma generated in the lower chamber. In this study, a fluid model was employed to investigate a dual cylindrical inductively coupled Ar/O₂ discharge. The effects of external parameters on electron density, electron temperature, O atomic density, and plasma uniformity in the main chamber were studied, and the reasons were analyzed. The results of this study show that remote power can control the plasma uniformity and increase the plasma density in the main chamber. As the remote power increased, plasma uniformity improved initially and then deteriorated. The main power affected the plasma density at the edge of the main chamber and can modulate the plasma density in the main chamber. The gas pressure affected both the uniformity and density of the plasma. As the gas pressure increased, the plasma uniformity deteriorated, but the free radical density improved.

Density limit has long been a widely studied issue influencing the operating range of tokamaks. The rapid growth of the m/n = 2/1 (where m and n are poloidal and toroidal mode numbers, respectively) tearing mode is generally regarded as a primary precursor to the density limit disruption. In this experiment, the coupling of the m/n = 1/1 mode and the m/n = 2/1 mode in high-density plasma was observed. During a sawtooth cycle, the frequencies of the two modes gradually converge until they become equal. After that, toroidal coupling occurs between the 1/1 and 2/1 modes, resulting in a mutually fixed phase relationship. With the occurrence of toroidal coupling, the 2/1 mode is stabilized. Prior to the disruption, the cessation of the 1/1 and 2/1 mode coupling, along with the rapid growth in the amplitude of the 2/1 mode, can be observed. Additionally, under the same parameters, comparing discharges with or without the 1/1 mode, it is found that the presence of the 1/1 mode leads to higher plasma density and temperature parameters.

A remote plasma, also referred to as a plasma plume (diffuse or filamentary), is normally formed downstream of an atmospheric pressure plasma jet. In this study, a diffuse plume is formed by increasing the bias voltage (U_b) applied to the downstream electrode of an argon plasma jet excited by a negatively pulsed voltage. The results indicate that the plume is filamentary when U_b is low, which transits to the diffuse plume with increasing U_b. The discharge initiated at the rising edge of the pulsed voltage is attributed to the diffuse plume, while that at the falling edge contributes to the filament in the plume. For the diffuse plume, the discharge intensity decreases with the increasing oxygen content (C_o). Fast photography reveals that the diffuse plume results from a negative streamer, which has a dark region near the nozzle with C_o = 0%. However, the dark region is absent with C_o = 0.5%. From the optical emission spectrum, the electron density, electron excitation temperature, gas temperature, and oxygen atom concentration are investigated.

The effect on the germination and seedling growth of radish (Raphanus sativus) seeds were examined employing a dielectric barrier discharge (DBD) at atmospheric pressure and room temperature for various treatment time. DBD plasma using argon gas of flow rate 2 l m⁻¹ was employed in this study. Radish seeds were treated with DBD plasma for 1–5 min, respectively. Germination characteristics, seedling growth parameters, the contact angle of the seed coat, water uptake capacity, mass loss, the temperature of the seeds, chlorophyll, and carotenoid contents of the seedlings were measured before and after the DBD plasma treatments. Plasma treatment of radish seeds significantly increased germination-related characters, including germination percentage, fresh and dry weight, vigor index, and total carotenoids contents. However, the cumulative production rate was found to be decreased. Results from the experiment indicate an acceleration in the water uptake of the radish seeds and make the seed surface hydrophilic by plasma treatment. Scanning electron microscopy analysis showed that etching effects on the seed coat occurred after the argon plasma treatments, which affected the wettability of the radish seed. The experimental findings showed that seeds being treated by DBD plasma for 2 and 3 min had a positive effect on the germination and seedling growth of radish.

Plasma-based processes, particularly in carbon capture and utilization, hold great potential for addressing environmental challenges and advancing a circular carbon economy. While significant progress has been made in understanding plasma-induced reactions, plasma-catalyst interactions, and reactor development to enhance energy efficiency and conversion, there remains a notable gap in research concerning overall process development. This review emphasizes the critical need for considerations at the process level, including integration and intensification, to facilitate the industrialization of plasma technology for chemical production. Discussions centered on the development of plasma-based processes are made with a primary focus on CO₂ conversion, offering insights to guide future work for the transition of the technology from laboratory scale to industrial applications. Identification of current research gaps, especially in upscaling and integrating plasma reactors with other process units, is the key to addressing critical issues. The review further delves into relevant research in process evaluation and assessment, providing methodological insights and highlighting key factors for comprehensive economic and sustainability analyses. Additionally, recent advancements in novel plasma systems are reviewed, presenting unique advantages and innovative concepts that could reshape the future of process development. This review provides essential information for navigating the path forward, ensuring a comprehensive understanding of challenges and opportunities in the development of plasma-based CCU process.

A key physics issue for achieving steady-state high-performance plasmas on EAST tokamak is to decrease beam-ion losses to improve plasma confinement during neutral beam injections (NBIs). To decrease the beam losses, previous counter-I_p NBI injections are upgraded to co-I_p injections. Analysis shows that due to the reversed direction of drift across the flux surfaces caused by the pitch angle, the beam prompt loss fraction decreases from about 49% to 3% after the upgrade. Moreover, because of the change of entire beam path, beam shine-through (ST) loss fraction for counter-I_p tangential and counter-I_p perpendicular injections is reversed to co-I_p tangential and co-I_p perpendicular injections, respectively. Due to the change in the initial trapped-confined beam ion fraction caused by the peaked pitch profiles, the losses induced by toroidal ripple field are also reversed after the upgrade. To further improve the beam-ion confinement under the present NBI layout, the amplitudes of toroidal field are increased from 1.75 to 2.20 T. Result shows that, due to the smaller orbit width and peaked pitch angle profile, the beam prompt loss power is lower with higher toroidal field. Due to the synergy of higher initial trapped-confined beam ion fraction and narrower Goldston-White-Boozer (GWB) boundary, the loss induced by ripple diffusion is higher with higher toroidal field. The combined effect of beam ST loss, prompt loss and ripple loss, contributes to the increase in beam ion density. The decrease in beam loss power enhances beam heating efficiency, especially the fraction of beam heating ions. Finally, comparison between simulation and measurement by ²³⁵U fission chamber (FC) indicates that the increase in neutron rate is mainly contributed by improvement of beam-ion confinement. This study can provide potential support for beam operation and high-T_i experiment on EAST tokamak.

Aiming at the gas discharge problem in electric aircraft, this work studies the gas discharge characteristics at low-temperature sub-atmospheric pressure. A gas discharge shooting platform was built, and the discharge process was photographed by intensified charge-coupled device (ICCD). A two-dimensional axisymmetric model of needle-plate electrode gas discharge was established, and three sets of Helmholtz equations were used to solve the photoionization. The results show that under the same voltage, the electric field intensity in the discharge process increases first, then decreases and finally increases again. The discharge speed increases with the increase of altitude, and the electron density in the streamer decreases with the increase of altitude. The development speed of the streamer in the middle stage is higher than that in the early stage, and the speed increases more obviously with the increase of altitude. The development speed of the streamer in the later stage is lower than that in the middle stage, but with the increase of altitude, the development speed of the streamer in the later stage is higher than that in the middle stage.

Flexible surface micro-discharge plasma is a non-thermal plasma technique used for treating wounds in a painless way, with significant efficacy for chronic or hard-to-heal wounds. In this study, a confined space was designed to simulate wound conditions, with gelatin used to simulate wound tissue. The distinction between open and confined spaces was explored, and the effects of temperature, humidity, discharge power and the gap size within the confined space on the plasma characteristics were analyzed. It was found that temperature, humidity and discharge power are important factors that affect the concentration distribution of active components and the mode transition between ozone and nitrogen oxides. Compared to open space, the concentration of ozone in confined space was relatively lower, which facilitated the formation of nitrogen oxides. In open space, the discharge was dominated by ozone initially. As the temperature, humidity and discharge power increased, nitrogen oxides in the gas-phase products were gradually detected. In confined space, nitrogen oxides can be detected at an early stage and at much higher concentrations than ozone concentration. Furthermore, as the gap of the confined space decreased, the concentration of ozone was observed to decrease while that of nitrate increased, and the rate of this concentration change was further accelerated at higher temperature and higher power. It was shown that ozone concentration decreased from 0.11 to 0.03 μmol and the nitrate concentration increased from 20.5 to 24.5 μmol when the spacing in the confined space was reduced from 5 to 1 mm, the temperature of the external discharge was controlled at 40 °C, and the discharge power was 12 W. In summary, this study reveals the formation and transformation mechanisms of active substances in air surface micro-discharge plasma within confined space, providing foundational data for its medical applications.

Surface modification of fabrics is an effective way to endow them with antifouling properties while still maintaining their key advantages such as comfort, softness and stretchability. Herein, an atmospheric pressure dielectric barrier discharge (DBD) plasma method is demonstrated for the processing of silk fabrics using 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS) as the precursor. The results showed the successful grafting of PFDS groups onto the surface of silk fabrics without causing damage. Meanwhile, the gas temperature is rather low during the whole processing procedure, suggesting the non-equilibrium characteristics of DBD plasma. The influence on fabrics of the processing parameters (PFDS concentration, plasma treatment time and plasma discharge power) was systematically investigated. An optimum processing condition was determined to be a PFDS concentration of 8wt%, a plasma processing time of 40 s and a plasma power of 11.87 W. However, with prolonged plasma processing time or enhanced plasma power, the plasma-grafted PFDS films could be degraded. Further study revealed that plasma processing of silk fabrics with PFDS would lead to a change in their chemical composition and surface roughness. As a result, the surface energy of the fabrics was reduced, accompanied by improved water and oil repellency as well as enhanced antifouling performance. Besides, the plasma-grafted PFDS films also had good durability and stability. By extending the method to polyester and wool against different oil-/water-based stains, the DBD plasma surface modification technique demonstrated good versatility in improving the antifouling properties of fabrics. This work provides guidance for the surface modification of fabrics using DBD plasma to confer them with desirable functionalities.

Microwave discharge plasma in liquid (MDPL) is a new type of water purification technology with a high mass transfer efficiency. It is a kind of low-temperature plasma technology. The reactive species produced by the discharge can efficiently act on the pollutants. To clarify the application prospects of MDPL in water treatment, the discharge performance, practical application, and pollutant degradation mechanism of MDPL were studied in this work. The effects of power, conductivity, pH, and Fe²⁺ concentration on the amount of reactive species produced by the discharge were explored. The most common and refractory perfluorinated compounds (perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in water environments are degraded by MDPL technology. The highest defluorination of PFOA was 98.8% and the highest defluorination of PFOS was 92.7%. The energy consumption efficiency of 50% defluorination (G_50-F) of PFOA degraded by MDPL is 78.43 mg/kWh, PFOS is 42.19 mg/kWh. The results show that the MDPL technology is more efficient and cleaner for the degradation of perfluorinated compounds. Finally, the reaction path and pollutant degradation mechanisms of MDPL production were analyzed. The results showed that MDPL technology can produce a variety of reactive species and has a good treatment effect for refractory perfluorinated pollutants.

Toroidal torques, generated by the resonant magnetic perturbation (RMP) and acting on the plasma column, are numerically systematically investigated for an ITER baseline scenario. The neoclassical toroidal viscosity (NTV), in particular the resonant portion, is found to provide the dominant contribution to the total toroidal torque under the slow plasma flow regime in ITER. While the electromagnetic torque always opposes the plasma flow, the toroidal torque associated with the Reynolds stress enhances the plasma flow independent of the flow direction. A peculiar double-peak structure for the net NTV torque is robustly computed for ITER, as the toroidal rotation frequency is scanned near the zero value. This structure is found to be ultimately due to a non-monotonic behavior of the wave-particle resonance integral (over the particle pitch angle) in the superbanana plateau NTV regime in ITER. These findings are qualitatively insensitive to variations of a range of factors including the wall resistivity, the plasma pedestal flow and the assumed frequency of the rotating RMP field.

Hydrogels are biomaterials with 3D networks of hydrophilic polymers. The generation of hydrogels is turning to the development of hydrogels with the help of enabling technologies. Plasma can tailor the hydrogels' properties through simultaneous physical and chemical actions, resulting in an emerging technology of plasma-activated hydrogels (PAH). PAH can be divided into functional PAH and biological tissue model PAH. This review systematically introduces the plasma sources, plasma etching polymer surface, and plasma cross-linking involved in the fabrication of PAH. The 'diffusion-drift-reaction model' is used to study the microscopic physicochemical interaction between plasma and biological tissue PAH models. Finally, the main achievements of PAH, including wound treatment, sterilization, 3D tumor model, etc, and their development trends are discussed.

Cold atmospheric plasmas (CAPs) have shown great applicability in agriculture. Many kinds of CAP sources have been studied in agricultural applications to promote plant growth and cure plant diseases. We briefly review the state-of-the-art stimulating effects of atmospheric-pressure dielectric-barrier-discharge (AP-DBD) plasmas, after the direct or indirect treatment of plants for growth promotion and disease control. We then discuss the special demands on the characteristics of the CAP sources for their applications in plant mutation breeding. An atmospheric and room temperature plasma (ARTP) jet generator with a large plasma irradiation area, a high enough concentration of chemically reactive species and a low gas temperature is designed for direct plant mutagenesis. Experimental measurements of the electrical, thermal and optical features of the ARTP generator are conducted. Then, an ARTP-P (ARTP for plant mutagenesis) mutation breeding machine is developed, and a typical case of plant mutation breeding by the ARTP-P mutation machine is presented using Coreopsis tinctoria Nutt. seeds. Physical and agricultural experiments show that the newly-developed ARTP-P mutation breeding machine with a large irradiation area can generate uniform CAP jets with high concentrations of chemically reactive species and mild gas temperatures, and have significant mutagenesis effects on the Coreopsis tinctoria Nutt. seeds. The ARTP-P mutation breeding machine may provide a platform for systematic studies on mutation mechanisms and results for various plant seeds under different operating conditions in future research.

This paper reviews the effects of resonant magnetic perturbation (RMP) on classical tearing modes (TMs) and neoclassical tearing modes (NTMs) from the theory, experimental discovery and numerical results with a focus on four major aspects: (i) mode mitigation, where the TM/NTM is totally suppressed or partly mitigated by the use of RMP; (ii) mode penetration, which means a linearly stable TM/NTM triggered by the externally applied RMP; (iii) mode locking, namely an existing rotating magnetic island braked and finally stopped by the RMP; (iv) mode unlocking, as the name suggests, it is the reverse of the mode locking process. The key mechanism and physical picture of above phenomena are revealed and summarized.

Atmospheric pressure cold plasma, with advantages such as high particle activity, no thermal damage, high efficiency and direct and friendly contact with human tissues, is considered to have great potential in biomedical applications. Therefore, 'plasma medicine' as a new interdiscipline has been developed in the past two decades. This review first briefly describes the development of typical plasma sources suitable for biomedical applications, and those with different discharge forms are simply compared, evaluated and summarized. Subsequently, measurement of the crucial gaseous reactive particles (e.g. OH and O) and their spatio-temporal distributions are introduced. Meanwhile, the generation and variation rules and the related critical macroscopic parameters of the plasma-induced aqueous reactive species are summarized. Finally, related studies in the last ten years on the mechanisms of the plasma-driven microbial inactivation and plasma-induced apoptosis of cancer cells are introduced. Moreover, some scientific problems that need to be urgently solved in the field of plasma medicine are also discussed. This review will provide useful guidance for future related research.

The influence of m/n = 2/1 (m and n are poloidal and toroidal mode numbers) tearing modes on plasma perpendicular flows and micro-fluctuations has been investigated in HL-2A neutral beam injection heated L-mode plasmas. It is found that the local perpendicular rotation velocity and turbulence energy are modulated by the alternation between the island X-point and O-point of the naturally rotating tearing modes. Cross-correlation analysis indicates that the modulation of density fluctuations by the tearing mode is not only limited to the island region, but also occurs in the edge region near the last closed flux surface. The turbulence exhibits distinct spectral characteristics inside and outside the island region. In addition, it is observed that the particle flux near the strike point is also significantly impacted by the tearing modes. The experimental evidence reveals that there are strong core-edge interactions between the core tearing modes and the edge transport.

The electromagnetic turbulence in reversed field pinch (RFP) plasmas exhibits three-dimensional characteristics. Suppression of this turbulence is crucial for enhancing plasma confinement, necessitating control over the electric field or the current profile. To this end, two sets of electrodes have been designed and installed on the Keda Torus eXperiment (KTX) RFP device to manipulate the edge electric field and the edge parallel current profile. Subsequently, the edge radial electric field and edge parallel current profile control experiments are conducted. In the edge radial electric field control experiments, the edge radial electric field is altered under bias, accompanied with an increase in the electron density and plasma duration. However, under bias, both electrostatic and magnetic fluctuations are enhanced. In the edge parallel current profile control experiments, the results indicate that bias modifies the edge parallel current profile locally, leading to a localized increase in the field reversal depth and electron density. Additionally, a reduction in magnetic fluctuations is observed within the reversed field enhanced region under bias, suggesting that the bias suppresses magnetic perturbations.

An atmospheric pressure plasma jet (APPJ) approach is developed to prepare platinum nanoparticles (PtNPs) under mild reaction conditions of lower temperatures and without adding chemical reagents. Optical Emission Spectroscopy (OES) and X-ray Photoelectron Spectroscopy (XPS) tests revealed that the APPJ contains a large number of high-energy active particles, which can generate solvated electrons in liquid thereby promoting the rapid reduction of Pt(IV) ions into Pt(0) atoms, and these atoms gradually grow into nanoparticles. After 3 min of treatment, PtNPs exhibit excellent dispersibility with a particle size distribution ranging from 1.8 to 2.8 nm. After 5 min, the particle size increases, and aggregation occurs. The zeta potentials for the two situations were −56.0 mV and −12.5 mV respectively. The results indicate that the treatment time has a significant impact on the dispersion, particle size distribution, and sol stability of the nanoparticles. Furthermore, it reveals the formation mechanism of PtNPs prepared by APPJ, which involves the generation and expansion of nanocrystalline nuclei, and the construction of negatively charged colloidal particles. The overall mechanism highlights the importance of the plasma-liquid interaction in the synthesis of PtNPs, offering a new perspective on the controllable production of nanomaterials using plasma technology.

Cold atmospheric plasma (CAP) has emerged as a promising technology for the degradation of organic dyes, but the underlying mechanisms at the molecular level remain poorly understood. Using density-functional tight-binding (DFTB)-based quantum chemical molecular dynamics at 300 K, we have performed numerical simulations to investigate the degradation mechanism of Disperse Red 1 interacting with CAP-generated oxygen radicals. One hundred direct-dynamics trajectories were calculated for up to 100 ps simulation time, after which hydrogen-abstraction, benzene ring-opening/expanding, formaldehyde formation and modification in the chromophoric azo group which can lead to color-losing were observed. The latter was obtained with yields of around 6 % at the given temperature. These findings not only enhance our understanding of CAP treatment processes but also have implications for the development of optimized purification systems for sustainable wastewater treatment. This study underscores the utility of DFTB simulations in unraveling complex chemical processes and guiding the design of advanced treatment strategies in the context of CAP technology.

The discharge and plasma characteristics of Ag magnetron sputtering discharge operated near the electron series resonance (ESR) oscillation, which was excited using the driving frequency of 27.12 MHz, was investigated. The imaginary part of impedance was found to undergo a transition from capacitive to inductive on varying radio-frequency (RF) power, and the conditions for the ESR excitation was satisfied. The current–voltage characteristic of discharge showed that the lower discharge voltage and higher current was an important feature of RF magnetron sputtering operated near the ESR oscillation, which was caused by the small impedance Z originated from the mutual compensation between the sheath capacitive reactance and the plasma inductive reactance. The higher electron temperature, ion flux density and ion energy as well as the moderate electron density were obtained. The interaction of higher energy ions on substrate surface improved the crystallographic quality of Ag films. Therefore, the 27.12 MHz magnetron sputtering operated near the ESR oscillation has better deposition characteristics than that of commercial 13.56 MHz RF magnetron sputtering.

The EHL-2 spherical torus is designed to demonstrate proton-boron fusion within a compact spherical tokamak. Its planned heating system includes a negative ion-based neutral beam injection (N-NBI), two positive ion-based NBI systems (P-NBI), electron cyclotron resonance heating (ECRH), ion cyclotron resonance heating (ICRH), and high harmonic fast wave (HHFW), with a total power output of 31 MW. According to scaling law estimates, the device is capable of achieving H-mode operation. The plasma density, $n_{e,min}$, at the minimum L-H power threshold, $P_{LH}$, is estimated to be $4.4\times10^{19}, \text{m}^{-3}$. The pedestal parameters were calculated using the REPED model. Assuming boron as the primary impurity ion, the predicted pedestal width and height are lower compared to the typical case with carbon impurities. The pedestal collisionality for EHL-2 is estimated to range between 0.06 and 0.17, indicating the potential for significant energy loss due to edge localized modes (ELMs). The heat flux on the divertor plate has been calculated using the JOREK code. The peak heat fluxes during ELM bursts are approximately 31.0 MW/m$^2$ at the lower inboard target and 39.5 MW/m$^2$ at the lower outboard target. A preliminary design of the resonant magnetic perturbation (RMP) coils has been completed to both control type-I ELMs and correct error fields. The system comprises 16 coils arranged into 2 $\times$ 4 pairs. In ELM control mode, a 14/2 component is generated at 1.7 G/kAt, with a current of 4.9 kA required to achieve $\sigma_{Chirikov} = 1$ at the resonant surface, where the normalized poloidal magnetic flux is 0.85. In error field (EF) modulation mode, 2/1 and 3/1 components are generated at 3.5 G/kAt and 2.8 G/kAt, respectively.