High fusion triple product has been obtained in the advanced scenarios with high normalized beta (βN) on the Experimental Advanced Superconducting Tokamak (EAST). A record value of ni0Ti0τE ∼ 1.0 × 1019 m−3 keV s for EAST deuterium plasma has been achieved, which is due to the formation of strong and broad internal transport barriers (ITBs) in ne, Te and Ti profiles. Analysis shows that the strong ITB formation could be attributed to the reduction of transport from ITG modes. Based on the analysis, the physical mechanisms and methods to further improve the plasma performance are discussed.
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Jianyuan XIAO and Hong QIN 2021 Plasma Sci. Technol. 23 055102
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.
Weisheng CUI et al 2021 Plasma Sci. Technol. 23 075402
The dielectric barrier discharge (DBD) in air at atmospheric pressure is not suitable for industrial applications due to its randomly distributed discharge filaments. In this paper, the influence of the electric field distribution on the uniformity of DBD is theoretically analyzed and experimentally verified. It is found that a certain degree of uneven electric field distributions can control the development of electron avalanches and regulate their transition to streamers in the gap. The discharge phenomena and electrical characteristics prove that an enhanced Townsend discharge can be formed in atmospheric-pressure air with a curved-plate electrode. The spectral analysis further confirms that the gas temperature of the plasma produced by the curved-plate electrode is close to room temperature, which is beneficial for industrial applications. This paper presents the relationship between the electron avalanche transition and the formation of a uniform DBD, which can provide some references for the development and applications of the DBD in the future.
Tetsutarou OISHI et al 2021 Plasma Sci. Technol. 23 084002
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.
Weisheng CUI and Ruobing ZHANG 2024 Plasma Sci. Technol. 26 042001
Atmospheric pressure cold plasma jets (APCPJs) typically exhibit a slender, conical structure, which imposes limitations on their application for surface modification due to the restricted treatment area. In this paper, we introduce a novel plasma jet morphology known as the large-scale cold plasma jet (LSCPJ), characterized by the presence of both a central conical plasma jet and a peripheral trumpet-like diffuse plasma jet. The experimental investigations have identified the factors influencing the conical and the trumpet-like diffuse plasma jet, and theoretical simulations have shed light on the role of the flow field and the electric field in shaping the formation of the LSCPJ. It is proved that, under conditions of elevated helium concentration, the distributions of impurity gas particles and the electric field jointly determine the plasma jet's morphology. High-speed ICCD camera images confirm the dynamic behavior of plasma bullets in LSCPJ, which is consistent with the theoretical analysis. Finally, it is demonstrated that when applied to the surface treatment of silicone rubber, LSCPJ can achieve a treatment area over 28 times larger than that of APCPJ under equivalent conditions. This paper uncovers the crucial role of impurity gases and electric fields in shaping plasma jet morphology and opens up the possibility of efficiently diversifying plasma jet generation effects through external electromagnetic fields. These insights hold the promise of reducing the generation cost of plasma jets and expanding their applications across various industrial sectors.
Lanlan NIE et al 2024 Plasma Sci. Technol. 26 043001
Plasma-enhanced transdermal drug delivery (TDD) presents advantages over traditional methods, including painless application, minimal skin damage, and rapid recovery of permeability. To harness its clinical potential, factors related to plasma's unique properties, such as reactive species and electric fields, must be carefully considered.This review provides a concise summary of conventional TDD methods and subsequently offers a comprehensive examination of the current state-of-the-art in plasma-enhanced TDD. This includes an analysis of the impact of plasma on HaCaT human keratinocyte cells, ex vivo/in vivo studies, and clinical research on plasma-assisted TDD. Moreover, the review explores the effects of plasma on skin physical characteristics such as microhole formation, transepidermal water loss (TEWL), molecular structure of the stratum corneum (SC), and skin resistance. Additionally, it discusses the involvement of various reactive agents in plasma-enhanced TDD, encompassing electric fields, charged particles, UV/VUV radiation, heat, and reactive species. Lastly, the review briefly addresses the temporal behavior of the skin after plasma treatment, safety considerations, and potential risks associated with plasma-enhanced TDD.
Meng SUN et al 2024 Plasma Sci. Technol. 26 064006
The characteristics of the blue core phenomenon observed in a divergent magnetic field helicon plasma are investigated using two different helical antennas, namely right-handed and left-handed helical antennas. The mode transition, discharge image, spatial profiles of plasma density and electron temperature are diagnosed using a Langmuir probe, a Nikon D90 camera, an intensified charge-coupled device camera and an optical emission spectrometer, respectively. The results demonstrated that the blue core phenomenon appeared in the upstream region of the discharge tube at a fixed magnetic field under both helical antennas. However, it is more likely to appear in a right-handed helical antenna, in which the plasma density and ionization rate of the helicon plasma are higher. The spatial profiles of the plasma density and electron temperature are also different in both axial and radial directions for these two kinds of helical antenna. The wavelength calculated based on the dispersion relation of the bounded whistler wave is consistent with the order of magnitude of plasma length. It is proved that the helicon plasma is part of the wave mode discharge mechanism.
Zhiyuan XU et al 2024 Plasma Sci. Technol. 26 044001
The environmental contamination caused by antibiotics is increasingly conspicuous due to their widespread manufacture and misuse. Plasma has been employed in recent years for the remediation of antibiotic pollution in the environment. In this work, a falling-film dielectric barrier discharge was used to degrade the antibiotic tetracycline (TC) in water. The reactor combined the gas-liquid discharge and active gas bubbling to improve the TC degradation performance. The discharge characteristics, chemical species' concentration, and degradation rates at different parameters were systematically studied. Under the optimized conditions (working gas was pure oxygen, liquid flow rate was 100 mL/min, gas flow rate was 1 L/min, voltage was 20 kV, single treatment), TC was removed beyond 70% in a single flow treatment with an energy efficiency of 145 mg/(kW·h). The reactor design facilitated gas and liquid flow in the plasma area to produce more ozone in bubbles after a single flow under pure oxygen conditions, affording fast TC degradation. Furthermore, long-term stationary experiment indicated that long-lived active species can sustain the degradation of TC. Compared with other plasma treatment systems, this work offers a fast and efficient degradation method, showing significant potential in practical industrial applications.
Xingyu CHEN et al 2024 Plasma Sci. Technol. 26 045403
The discharge morphology of pulsed dielectric barrier discharge (PDBD) plays important roles in its applications. Here, we systematically investigated the effects of the voltage amplitude, discharge gap, and O2 content on the PDBD morphology, and revealed the possible underlying mechanism of the U-shaped formation. First, the morphological evolution under different conditions was recorded. A unique U-shaped region appears in the middle edge region when the gap is larger than 2 mm, while the entire discharge region remains columnar under a 2 mm gap in He PDBD. The width of the discharge and the U-shaped region increase with the increase in voltage, and decrease with the increase of the gap and O2 content. To explain this phenomenon, a two-dimensional symmetric model was developed to simulate the spatiotemporal evolution of different species and calculate the electric thrust. The discharge morphology evolution directly corresponds to the excited-state atomic reduction process. The electric thrust on the charged particles mainly determines the reaction region and strongly influences the U-shaped formation. When the gap is less than 2 mm, the electric thrust is homogeneous throughout the entire region, resulting in a columnar shape. However, when the gap is larger than 2 mm or O2 is added, the electric thrust in the edge region becomes greater than that in the middle, leading to the U-shaped formation. Furthermore, in He PDBD, the charged particles generating electric thrust are mainly electrons and helium ions, while in He/O2 PDBD those that generate electric thrust at the outer edge of the electrode surface are mainly various oxygen-containing ions.
Weijie HUO et al 2024 Plasma Sci. Technol. 26 055501
In this study, a pulsed, high voltage driven hollow-cathode electron beam sources through an optical trigger is designed with characteristics of simple structure, low cost, and easy triggering. To validate the new design, the characteristics of hollow-cathode discharge and electron beam characterization under pulsed high voltage drive are studied experimentally and discussed by discharge characteristics and analyses of waveform details, respectively. The validation experiments indicate that the pulsed high voltage supply significantly improves the frequency and stability of the discharge, which provides a new solution for the realization of a high-frequency, high-energy electron beam source. The peak current amplitude in the high-energy electron beam increases from 6.2 A to 79.6 A, which indicates the pulsed power mode significantly improves the electron beam performance. Besides, increasing the capacitance significantly affects the high-current, lower-energy electron beam more than the high-energy electron beam.
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Xiangbei WU et al 2024 Plasma Sci. Technol. 26 064001
The bipolar ionic liquid thruster employs ionic liquid as a propellant to discharge positively and negatively charged high-energy particles under an alternating current (AC) power source, effectively suppressing electrochemical reaction and ensuring charge neutrality. Determining an optimal AC supply power source frequency is critical for sustained stable thruster operation. This study focuses on the emission characteristics of the ionic liquid thruster under varied AC conditions. The AC power supply was set within the frequency range of 0.5–64 Hz, with eight specific frequency conditions selected for experimentation. The experimental results indicate that the thruster operates steadily within a voltage range of ±1470 to ±1920 V, with corresponding positive polarity current ranging from 0.41 to 4.91 μA and negative polarity current ranging from −0.49 to −4.10 μA. During voltage polarity switching, an emission delay occurs, manifested as a prominent peak signal caused by circuit capacitance characteristics and a minor peak signal resulting from liquid droplets. Extended emission test was conducted at 16 Hz, demonstrating approximately 1 h and 50 min of consistent emission before intermittent discharge. These findings underscore the favorable impact of AC conditions within the 8–16 Hz range on the self-neutralization capability of the ionic liquid thruster.
Na LI et al 2024 Plasma Sci. Technol. 26 064002
In this paper, high-energy Ne ions were used to irradiate Zr63.5Cu23Al9Fe4.5 metallic glass (MG) and crystalline W to investigate their difference in mechanical response after irradiation. The results showed that with the irradiation dose increased, the tensile micro-strain increased, nano-hardness increased from 7.11 GPa to 7.90 GPa and 8.62 GPa, Young's modulus increased, and H3/E2 increased which indicating that the plastic deformability decreased in crystalline W. Under the same irradiation conditions, the Zr63.5Cu23Al9Fe4.5 MG still maintained the amorphous structure and became more disordered despite the longer range and stronger displacement damage of Ne ions in Zr63.5Cu23Al9Fe4.5 MG than in crystalline W. Unlike the irradiation hardening and embrittlement behavior of crystalline W, Zr63.5Cu23Al9Fe4.5 MG showed the gradual decrease in hardness from 6.02 GPa to 5.89 GPa and 5.50 GPa, the decrease in modulus and the increase in plastic deformability with the increasing dose. Possibly, the irradiation softening and toughening phenomenon of Zr63.5Cu23Al9Fe4.5 MG could provide new ideas for the design of nuclear materials.
Xiaofang XU et al 2024 Plasma Sci. Technol. 26 064005
Ammonia is one of the most important chemical raw materials in both manufacture and life of human. Traditionally Haber-Bosch method for ammonia synthesis involves high temperature and high pressure conditions, leading to significant energy consumption and environmental pollution. Non-thermal plasma (NTP) is a promising alternative approach to ammonia synthesis at low temperature and atmospheric pressure. In this study, the synergistic effect of nanosecond pulsed dielectric barrier discharge (np-DBD) and Ni-MOF-74 catalyst was investigated in ammonia synthesis by utilizing nitrogen and hydrogen as feedstock. The results demonstrated that the plasma catalytic-synthesis process parameters play a crucial role in the synthesis process of ammonia. The highest ammonia synthesis rate of 5145.16 μmol·g−1·h−1 with an energy efficiency of 1.27 g·kWh−1 was observed in the presence of the Ni-MOF-74 catalyst, which was 3.7 times higher than that without Ni-MOF-74 catalyst. The synergistic effect of Ni-MOF-74 catalyst and nanosecond pulsed plasma was explored by in-situ plasma discharge diagnostics.
Shouxian TANG et al 2024 Plasma Sci. Technol. 26 064004
Supported Pd catalyst is an important noble metal material in recent years due to its high catalytic performance in CO2 hydrogenation. A fluidized-bed plasma assisted atomic layer deposition (FP-ALD) process is reported to fabricate Pd nanoparticle catalyst over γ-Al2O3 or Fe2O3/γ-Al2O3 support, using palladium hexafluoroacetylacetonate as the Pd precursor and H2 plasma as counter-reactant. Scanning transmission electron microscopy exhibits that high-density Pd nanoparticles are uniformly dispersed over Fe2O3/γ-Al2O3 support with an average diameter of 4.4 nm. The deposited Pd-Fe2O3/γ-Al2O3 shows excellent catalytic performance for CO2 hydrogenation in a dielectric barrier discharge reactor. Under a typical condition of H2 to CO2 ratio of 4 in the feed gas, the discharge power of 19.6 W, and gas hourly space velocity of 10000 h−1, the conversion of CO2 is as high as 16.3% with CH3OH and CH4 selectivities of 26.5% and 3.9%, respectively.
Zongqi XU et al 2024 Plasma Sci. Technol. 26 065501
The common propellants used for electric thrusters, such as xenon and krypton, are rare, expensive, and difficult to acquire. Solid iodine attracts much attention with the advantages of low cost, extensive availability, low vapor pressure, and ionization potential. The performance of a low-power iodine-fed Hall thruster matched with a xenon-fed cathode is investigated across a broad range of operation conditions. Regulation of the iodine vapor's mass flow rates is stably achieved by using a temperature control method of the iodine reservoir. The thrust measurements are finished utilizing a thrust target during the tests. Results show that thrust and anode-specific impulse increase approximately linearly with the increasing iodine mass flow rate. At the nominal power of 200 W class, iodine mass flow rates are 0.62 and 0.93 mg/s, thrusts are 7.19 and 7.58 mN, anode specific impulses are 1184 and 826 s, anode efficiencies are 20.8% and 14.5%, and thrust to power ratios are 35.9 and 37.9 mN/kW under the conditions of 250 V, 0.8 A and 200 V, 1.0 A, respectively. The operating characteristics of iodine-fed Hall thruster are analyzed in different states. Further work on the measurements of plasma characteristics and experimental optimization will be carried out.
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Jiacheng LI et al 2023 Plasma Sci. Technol. 25 093001
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.
Heping LI et al 2022 Plasma Sci. Technol. 24 093001
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.
Zhengxiong WANG et al 2022 Plasma Sci. Technol. 24 033001
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.
Zimu XU et al 2020 Plasma Sci. Technol. 22 103001
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.
Min JIANG et al 2020 Plasma Sci. Technol. 22 080501
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.
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Sun et al
Electrons can escape from the cathode surface by acquiring enough energy greater than the work function or weakening the potential barrier at the cathode surface through tunneling effects in gas discharges, which plays a dominant role in the plasma-cathode interactions and is a key factor in many plasma phenomena and industrial applications. It is necessary to illustrate the various electron emission mechanisms and corresponding applicable description models to evaluate the impacts on discharge properties, especially for numerical simulation studies. However, most current researches usually rely on previous experience to select the appropriate simplified formula to calculate the electron emission current density, and there is little work that can explicitly give the application range of the simplified formulas for describing electron emission. In this work, the detailed expressions of the simplified formulas valid for field emission to thermo-field emission to thermionic emission typically used in the numerical simulation are proposed, and corresponding application ranges are determined in the framework of the Murphy-Good theory, which is commonly regarded as the general model and to be accurate in the full range of conditions of validity of the theory. The dimensionless parametrization is used to evaluate the emission current density of the Murphy-Good formula and a deviation factor is defined to obtain the application ranges for different work functions (2.5~5 eV), different cathode temperatures (300~6000 K), and different emitted electric field (105 ~1010 V‧m-1). The deviation factor is shown to be a non-monotonic function of the three parameters. A comparative study of particle number densities in atmospheric gas discharge with tungsten cathode is performed based on the one-dimensional implicit particle-in-cell with the Monte Carlo Collision (PIC-MCC) method according to the above application ranges. It is found that small differences in emission current density can lead to variation in the distributions of particle number density due to the change of collisional environment. This present work can provide a theoretical basis to select emission models for the subsequent numerical simulation.
Xiong et al
Discharge plasma parameter measurement is a key focus in low-temperature plasma research. Traditional diagnostics often require costly equipment, whereas electro-acoustic signals provide a rich, non-invasive, and less complex source of discharge information. This study harnesses machine learning to decode these signals. It establishes links between electro-acoustic signals and gas discharge parameters, such as power and distance, thus streamlining the prediction process. By building a spark discharge platform to collect electro-acoustic signals and implementing a series of acoustic signal processing techniques, the Mel-Frequency Cepstral Coefficients (MFCCs) of the acoustic signals are extracted to construct the predictors. Three machine learning models (Linear Regression, k-Nearest Neighbors, and Random Forest) are introduced and applied to the predictors to achieve real-time rapid diagnostic measurement of typical spark discharge power and discharge distance. All models display impressive performance in prediction precision and fitting abilities. Among them, the k-Nearest Neighbors model shows the best performance on discharge power prediction with the lowest mean square error (MSE=0.00571) and the highest R-squared value (R^2=0.93877). The experimental results show that the relationship between the electro-acoustic signal and the gas discharge power and distance can be effectively constructed based on the machine learning algorithm, which provides a new idea and basis for the online monitoring and real-time diagnosis of plasma parameters.
Ashikawa et al
In Large Helical Device (LHD), diborane (B2H6) is used as a standard boron source for boronization, which is assisted by helium glow discharges. In 2019, a new Impurity Powder Dropper (IPD) system has been installed and is under evaluation as a real-time wall conditioning technique. In LHD), which is a large size heliotron device, an additional helium (He) glow discharge cleaning (GDC) after boronization has been operated for a reduction of hydrogen recycling from coated boron layers, and this operational time of 3 h was determined by spectroscopic data during glow discharges. A flat hydrogen profile is obtained on the top surface of coated boron on the specimen exposed to boronization, the result suggests a reduction of hydrogen at the top surface by He-GDC. Trapped oxygen in coated boron was obtained by boronization, and the coated boron, which has boron-oxide, on the first wall by B-IPD was also shown. 
Considering the difference in coating areas between B2H6 boronization and B-IPD operation, it would be most effective to use the IPD and B2H6 boronization coating together for optimized wall conditioning.


Lu et al
The CLT code is used to quantitatively study the impact of toroidal mode coupling on the explosive dynamics of m/n = 3/1 double tearing mode. This work focuses on the explosive reconnection processes in which energy bursts and the main mode no longer dominates when the separation between two rational surfaces is relatively large in the medium range. The development of higher m and n modes is facilitated by a relatively large separation between two rational surfaces, a small qmin (the minimum value of safety factor), or a low resistivity. The relationships between the higher m and n modes development, explosive reconnection rate and the position exchange of 3/1 islands are summarized for the first time. The separation plays a more important role than qmin on enhancing the development of higher m and n modes. At a relatively large separation, the well development of higher m and n modes greatly reduces the reconnection rate, and suppresses the development of the main mode, resulting in the main mode not being able to develop sufficiently large to generate the position changes of 3/1 islands.
Zhang et al
Particle-In-Cell (PIC) simulations were performed in this work to study the dynamics of the EUV induced hydrogen plasma. Monte-Carlo Collision (MCC) model was employed to deal with the collisions between charged particles and background gas molecules. The dynamic evolution of the plasma sheath, as well as the flux and energy distribution of ions impact on the mirror surface, was discussed. It was found that the emission of secondary electrons under the EUV irradiation on the ruthenium coating of mirrors creates a positively charged wall and then prevents the ion from impacting onto the mirror and therefore changes the flux and energy distribution of ions reach the mirror. Furthermore, gas pressure has notable effect on the plasma sheath and the characteristics of the ions impinging on the mirrors. With greater gas pressure, the sheath potential decreases more rapidly. The flux of ions received by the mirror grows approximately linearly and the energy corresponding to the peak flux decreases slightly in the meantime. Meanwhile, EUV source intensity barely changes the sheath potential and its influence on the ion impact is mainly limited to the approximate linear increase of ion flux.