Pub Date : 2024-07-14DOI: 10.1088/2058-6272/ad62d5
Mingjie Zhou, Haiyun Tan, L. Zhuge, Xuemei Wu
In this work, we found a kind of edge state located at the interface between plasma photonic crystals (PPCs) and traditional photonic crystals, which depends on the property of the photonic band gap rather than the surface defect. Simulation and theoretical analysis show that by adjusting plasma density, we can change the topological characteristics of the photonic bandgap of PPCs, making it different from the photonic bandgap of traditional PCs, and thus excite or close the topological edge states. We further discussed the influence of plasma parameters on edge state characteristics, and the results showed that as the plasma density increased, the first photonic band gap (PBG) of the PPCs would be closed and then be reopened, resulting in band inversion and a change in the PBG properties of the PPCs. We can control the generation of edge states through plasma, and adjust the frequency and strength of the edge states. After the appearance of edge states, as the plasma density further increases, the first PBG of the PPCs will shift towards high frequencies and deepen. The frequency of edge states will shift towards higher frequencies, and their strength will also increase. We increased the first PBG depth of the PPCs by increasing the number of arrays, and found that when the number of the PPCs arrays increased, only the intensity of edge states would increase while the frequency remained unchanged. Therefore, flexible adjustment of edge states frequency and intensity can be achieved through the parameters of plasma density and array quantity. Our work demonstrates the properties of non-trivial edge states in plasma photonic crystals, which we believe can provide some guidance for applications based on edge states.
{"title":"Tunable topological edge state in plasma photonic crystals","authors":"Mingjie Zhou, Haiyun Tan, L. Zhuge, Xuemei Wu","doi":"10.1088/2058-6272/ad62d5","DOIUrl":"https://doi.org/10.1088/2058-6272/ad62d5","url":null,"abstract":"\u0000 In this work, we found a kind of edge state located at the interface between plasma photonic crystals (PPCs) and traditional photonic crystals, which depends on the property of the photonic band gap rather than the surface defect. Simulation and theoretical analysis show that by adjusting plasma density, we can change the topological characteristics of the photonic bandgap of PPCs, making it different from the photonic bandgap of traditional PCs, and thus excite or close the topological edge states. We further discussed the influence of plasma parameters on edge state characteristics, and the results showed that as the plasma density increased, the first photonic band gap (PBG) of the PPCs would be closed and then be reopened, resulting in band inversion and a change in the PBG properties of the PPCs. We can control the generation of edge states through plasma, and adjust the frequency and strength of the edge states. After the appearance of edge states, as the plasma density further increases, the first PBG of the PPCs will shift towards high frequencies and deepen. The frequency of edge states will shift towards higher frequencies, and their strength will also increase. We increased the first PBG depth of the PPCs by increasing the number of arrays, and found that when the number of the PPCs arrays increased, only the intensity of edge states would increase while the frequency remained unchanged. Therefore, flexible adjustment of edge states frequency and intensity can be achieved through the parameters of plasma density and array quantity. Our work demonstrates the properties of non-trivial edge states in plasma photonic crystals, which we believe can provide some guidance for applications based on edge states.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"53 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141650526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-12DOI: 10.1088/2058-6272/ad62aa
V. Siju, Santosh Pandya, S. K. Pathak, Ansh Patel, U. Nagora, Shishir Purohit, Samir K. Jha, Manoj Gupta, K. Tahiliani, Rohit Kumar Gupta, R. Tanna, Joydeep Ghosh
This paper describes the experimental analysis and preliminary investigation on the predictability of Pitch Angle Scattering (PAS) events through the Electron Cyclotron Emission (ECE) Radiometer signals at the ADITYA-Upgrade (ADITYA-U) tokamak. For low density discharges at ADITYA-U, a sudden abnormal rise is observed in the ECE signature while other plasma parameters are unchanged. Investigations are done to understand this abrupt rise that is expected to occur due to PAS. The rise time is as fast as 100 µs with a single step and/or multiple steps rise in ECE radiometer measurements. This event is known to limit the on-axis energy of runaway electrons. Being a repetitive event, the conditions of its repetitive occurrence can be investigated and thereby exploring the possibility of it being triggered and surveyed as an alternate runaway electron mitigation plan. Functional parameterization of such events with other discharge parameters is obtained and the possibility to trigger these events is discussed. PREDICT code is used to investigate the possible interpretations for the PAS occurrence through modeling and support the ECE observations. The trigger values so obtained experimentally are set as input criteria for PAS occurrence. Preliminary modeling investigations provide reliable consistency with the findings.
本文介绍了通过电子回旋加速器发射（ECE）辐射计信号对ADITYA-U（ADITYA-U）托卡马克的俯仰角散射（PAS）事件的可预测性进行的实验分析和初步研究。对于ADITYA-U的低密度放电，在其他等离子体参数不变的情况下，ECE信号会突然异常上升。为了理解这种预计由 PAS 引起的突然上升，我们进行了调查。上升时间快达 100 微秒，在 ECE 辐射计测量中出现单级和/或多级上升。众所周知，这一事件会限制失控电子的轴上能量。作为一种重复发生的事件，可以对其重复发生的条件进行研究，从而探索其触发的可能性，并将其作为一种替代的失控电子缓解计划进行调查。我们获得了此类事件与其他放电参数的功能参数化，并讨论了触发这些事件的可能性。PREDICT 代码用于通过建模研究 PAS 发生的可能解释，并为欧洲经委会的观测提供支持。通过实验获得的触发值被设定为 PAS 发生的输入标准。初步的建模调查与研究结果具有可靠的一致性。
{"title":"Investigating the occurrence and predictability of Pitch Angle Scattering events at ADITYA-Upgrade tokamak with the electron cyclotron emission radiometer","authors":"V. Siju, Santosh Pandya, S. K. Pathak, Ansh Patel, U. Nagora, Shishir Purohit, Samir K. Jha, Manoj Gupta, K. Tahiliani, Rohit Kumar Gupta, R. Tanna, Joydeep Ghosh","doi":"10.1088/2058-6272/ad62aa","DOIUrl":"https://doi.org/10.1088/2058-6272/ad62aa","url":null,"abstract":"\u0000 This paper describes the experimental analysis and preliminary investigation on the predictability of Pitch Angle Scattering (PAS) events through the Electron Cyclotron Emission (ECE) Radiometer signals at the ADITYA-Upgrade (ADITYA-U) tokamak. For low density discharges at ADITYA-U, a sudden abnormal rise is observed in the ECE signature while other plasma parameters are unchanged. Investigations are done to understand this abrupt rise that is expected to occur due to PAS. The rise time is as fast as 100 µs with a single step and/or multiple steps rise in ECE radiometer measurements. This event is known to limit the on-axis energy of runaway electrons. Being a repetitive event, the conditions of its repetitive occurrence can be investigated and thereby exploring the possibility of it being triggered and surveyed as an alternate runaway electron mitigation plan. Functional parameterization of such events with other discharge parameters is obtained and the possibility to trigger these events is discussed. PREDICT code is used to investigate the possible interpretations for the PAS occurrence through modeling and support the ECE observations. The trigger values so obtained experimentally are set as input criteria for PAS occurrence. Preliminary modeling investigations provide reliable consistency with the findings.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141654079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the H-mode experiments conducted on the Experimental Advanced Superconducting Tokamak (EAST), fluctuations induced by the so-called edge localized modes (ELMs) are captured by a high-speed vacuum ultraviolet (VUV) imaging system. Clear field line-aligned filamentary structures are analyzed in this work. Ion transport induced by ELM filaments in the SOL under different discharge conditions is analyzed by comparing the VUV signals with the divertor probe signals. It is found that convective transport along open field lines towards the divertor target dominates the parallel ion particle transport mechanism during ELMs. The toroidal mode number of the filamentary structure derived from the VUV images increases with the electron density pedestal height. The analysis of the toroidal distribution characteristics during ELM bursts reveals toroidal asymmetry. The influence of resonance magnetic perturbation (RMP) on the ELM size is also analyzed using VUV imaging data. When the phase difference of the coil changes periodically, the widths of the filaments change as well. Additionally, the temporal evolution of the ELMs on the VUV signals provides rise time and decay time for each single ELM event, and the results indicate a negative correlation trend between these two times.
在先进超导实验托卡马克（EAST）上进行的 H 模式实验中，高速真空紫外线（VUV）成像系统捕捉到了所谓的边缘局部模式（ELM）引起的波动。这项工作分析了清晰的场线对齐丝状结构。通过比较 VUV 信号和分流器探头信号，分析了不同放电条件下 SOL 中 ELM 细丝引起的离子传输。研究发现，在 ELM 过程中，沿开放场线向分流靶的对流传输在平行离子粒子传输机制中占主导地位。根据紫外可见光图像得出的丝状结构环形模数随电子密度基座高度的增加而增加。对 ELM 爆发期间环状分布特征的分析表明了环状分布的不对称性。此外，还利用紫外成像数据分析了共振磁扰动（RMP）对 ELM 尺寸的影响。当线圈的相位差发生周期性变化时，灯丝的宽度也会发生变化。此外，VUV 信号上 ELM 的时间演变提供了每个单一 ELM 事件的上升时间和衰减时间，结果表明这两个时间之间呈负相关趋势。
{"title":"VUV imaging of type-Ⅰ ELM filamentary structures and their temporal characteristics on EAST","authors":"R. Deng, Tingfeng Ming, Bang Li, Q. Shi, S.W. Hou, Shuqi Yang, Xiaoju Liu, Shaocheng Liu, Guoqiang Li, Xiang Gao, Yasuhiro Suzuki, Yunfeng Liang","doi":"10.1088/2058-6272/ad621c","DOIUrl":"https://doi.org/10.1088/2058-6272/ad621c","url":null,"abstract":"\u0000 In the H-mode experiments conducted on the Experimental Advanced Superconducting Tokamak (EAST), fluctuations induced by the so-called edge localized modes (ELMs) are captured by a high-speed vacuum ultraviolet (VUV) imaging system. Clear field line-aligned filamentary structures are analyzed in this work. Ion transport induced by ELM filaments in the SOL under different discharge conditions is analyzed by comparing the VUV signals with the divertor probe signals. It is found that convective transport along open field lines towards the divertor target dominates the parallel ion particle transport mechanism during ELMs. The toroidal mode number of the filamentary structure derived from the VUV images increases with the electron density pedestal height. The analysis of the toroidal distribution characteristics during ELM bursts reveals toroidal asymmetry. The influence of resonance magnetic perturbation (RMP) on the ELM size is also analyzed using VUV imaging data. When the phase difference of the coil changes periodically, the widths of the filaments change as well. Additionally, the temporal evolution of the ELMs on the VUV signals provides rise time and decay time for each single ELM event, and the results indicate a negative correlation trend between these two times.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"89 25","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141657645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-10DOI: 10.1088/2058-6272/ad61a2
Min Zhu, Yuchen Ping, Yinghao Zhang, Chaohai Zhang, Shuqun Wu
In this work, a gas-solid two-phase gliding arc discharge (GS-GAD) reactor was built. Gliding arc was formed in the gap between the blade electrodes, and solid powder was deposited on the sieve plate positioned beneath the blade electrodes. A range of experimental parameters, including the inter-electrode spacing, gas flow rate, applied voltage, and the type of the powder, were systematically varied to elucidate the influence of solid powder matter on the dynamics of gliding arc discharge (GAD). The discharge images were captured by ICCD and digital camera to investigate the mass transfer characteristics of GS-GAD, and the electrical parameters, such as the effective values of voltage, current, and discharge power were record to reveal the discharge characteristics of GS-GAD. The results demonstrate that powder undergoes spontaneous movement towards the upper region of the gliding arc due to the influence of electric field force. Increasing the discharge voltage, decreasing relative dielectric constant of the powder and reducing the electrode-to-sieve-plate distance all contribute to a greater involvement of powder in the GAD process, subsequently resulting in an enhanced powder concentration within the GAD region. Additionally, powder located beneath the gliding arc experiences downward resistance caused by the opposing gas flow and arc. Excessive gas flow rate notably hampers the powder concentration within the discharge region, and the velocity of powder motion in the upper part of the GAD region is reduced. Under the condition of electrode-to-sieve-plate distance of 30 mm, gas flow rate of 1.5 L/min, and peak-to-peak voltage of 31 kV, the best combination of arc gliding and powder spark discharge phenomena can be achieved with the addition of Al2O3 powder.
{"title":"Discharge and mass transfer characteristics of atmospheric pressure gas-solid two-phase gliding arc","authors":"Min Zhu, Yuchen Ping, Yinghao Zhang, Chaohai Zhang, Shuqun Wu","doi":"10.1088/2058-6272/ad61a2","DOIUrl":"https://doi.org/10.1088/2058-6272/ad61a2","url":null,"abstract":"\u0000 In this work, a gas-solid two-phase gliding arc discharge (GS-GAD) reactor was built. Gliding arc was formed in the gap between the blade electrodes, and solid powder was deposited on the sieve plate positioned beneath the blade electrodes. A range of experimental parameters, including the inter-electrode spacing, gas flow rate, applied voltage, and the type of the powder, were systematically varied to elucidate the influence of solid powder matter on the dynamics of gliding arc discharge (GAD). The discharge images were captured by ICCD and digital camera to investigate the mass transfer characteristics of GS-GAD, and the electrical parameters, such as the effective values of voltage, current, and discharge power were record to reveal the discharge characteristics of GS-GAD. The results demonstrate that powder undergoes spontaneous movement towards the upper region of the gliding arc due to the influence of electric field force. Increasing the discharge voltage, decreasing relative dielectric constant of the powder and reducing the electrode-to-sieve-plate distance all contribute to a greater involvement of powder in the GAD process, subsequently resulting in an enhanced powder concentration within the GAD region. Additionally, powder located beneath the gliding arc experiences downward resistance caused by the opposing gas flow and arc. Excessive gas flow rate notably hampers the powder concentration within the discharge region, and the velocity of powder motion in the upper part of the GAD region is reduced. Under the condition of electrode-to-sieve-plate distance of 30 mm, gas flow rate of 1.5 L/min, and peak-to-peak voltage of 31 kV, the best combination of arc gliding and powder spark discharge phenomena can be achieved with the addition of Al2O3 powder.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"86 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141663004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1088/2058-6272/ad60f4
Tao Lan, Chen Chen, C. Xiao, Weixing Ding, Jie Wu, W. Mao, Sen Zhang, Defeng Kong, Shoubiao Zhang, Zhengwei Wu, Qi Dong, Yongkang Zhou, Hangqi Xu, Jiaren Wu, Zian Wei, X. Wen, Chu Zhou, Adi Liu, Hong Li, Jinlin Xie, Wandong Liu, Zhuang Ge
A new compact torus injector (KTX-CTI) has been built for injection experiments on the Keda Torus eXperiment (KTX) reversed field pinch (RFP). The aim is to study the fundamental physics governing the compact torus (CT) central fueling processes. In experiments conducted under the sole influence of a 0.1 T toroidal magnetic field, the injected CT successfully penetrated the entire toroidal magnetic field, reaching the inner wall of the KTX vacuum vessel. Upon reaching the inner wall, the CT diffused both radially outward and toroidally within the vessel at a discernible diffusion speed. Moreover, the inherent helicity within the CT induced a modest KTX plasma current of 200A, consistent with predictions based on helicity conservation. CT injection demonstrated the capability to initiate KTX discharges at low loop voltages, suggesting its potential as a pre-ionization and current startup technique. During RFP discharges featuring CT injection, the central plasma density was found to exceed the Greenwald density limit, with more peaked density profiles, indicating the predominant confinement of CT plasma within the core region of the KTX bulk plasma.
{"title":"Preliminary compact torus injection experiments on the Keda Torus eXperiment reversed field pinch","authors":"Tao Lan, Chen Chen, C. Xiao, Weixing Ding, Jie Wu, W. Mao, Sen Zhang, Defeng Kong, Shoubiao Zhang, Zhengwei Wu, Qi Dong, Yongkang Zhou, Hangqi Xu, Jiaren Wu, Zian Wei, X. Wen, Chu Zhou, Adi Liu, Hong Li, Jinlin Xie, Wandong Liu, Zhuang Ge","doi":"10.1088/2058-6272/ad60f4","DOIUrl":"https://doi.org/10.1088/2058-6272/ad60f4","url":null,"abstract":"\u0000 A new compact torus injector (KTX-CTI) has been built for injection experiments on the Keda Torus eXperiment (KTX) reversed field pinch (RFP). The aim is to study the fundamental physics governing the compact torus (CT) central fueling processes. In experiments conducted under the sole influence of a 0.1 T toroidal magnetic field, the injected CT successfully penetrated the entire toroidal magnetic field, reaching the inner wall of the KTX vacuum vessel. Upon reaching the inner wall, the CT diffused both radially outward and toroidally within the vessel at a discernible diffusion speed. Moreover, the inherent helicity within the CT induced a modest KTX plasma current of 200A, consistent with predictions based on helicity conservation. CT injection demonstrated the capability to initiate KTX discharges at low loop voltages, suggesting its potential as a pre-ionization and current startup technique. During RFP discharges featuring CT injection, the central plasma density was found to exceed the Greenwald density limit, with more peaked density profiles, indicating the predominant confinement of CT plasma within the core region of the KTX bulk plasma.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"68 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141664554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In numerical simulations of the ion cyclotron range of frequencies (ICRF) wave heating scheme, core solvers usually focus on wave propagation and absorption mechanisms within the core plasma region. However, the realistic scrape-off layer (SOL) plasma is usually simplified, making it difficult to have deeper understanding of wave propagation and absorption within the SOL. In this work, we employ a cold plasma assumption and an artificial absorption mechanism based on the approach of reference (Zhang et al 2022 Nucl. Fusion 62 076032), to study wave propagation and absorption in the realistic SOL plasma of the EAST. During the exponential decay of the total coupled power with respect to the toroidal mode numbers, several fluctuations are observed in the case of low collisional frequencies. The fluctuations may be caused by the cavity modes associated with specific toroidal mode numbers. Due to the presence of cutoff densities, the edge power losses and the total coupled power exhibit different behaviors before and after the cut-off layer is “open”. Furthermore, the simulation results obtained from the kinetic model in reference (Zhang et al 2022 Nucl. Fusion 62 076032) is discussed. This suggests that both the core-edge combined model and the artificial mechanism are capable of simulating wave propagation and absorption.
在离子回旋频率范围（ICRF）波加热方案的数值模拟中，核心求解器通常侧重于核心等离子体区域内的波传播和吸收机制。然而，现实中的刮除层（SOL）等离子体通常是简化的，因此很难深入理解 SOL 内的波传播和吸收。在这项工作中，我们根据参考文献（Zhang et al 2022 Nucl. Fusion 62 076032）的方法，采用冷等离子体假设和人工吸收机制来研究 EAST 的现实 SOL 等离子体中的波传播和吸收。在总耦合功率相对于环模数的指数衰减过程中，在低碰撞频率的情况下观察到一些波动。这些波动可能是由与特定环形模数相关的空腔模引起的。由于存在截止密度，边缘功率损耗和总耦合功率在截止层 "打开 "前后表现出不同的行为。此外，还讨论了参考文献（Zhang et al 2022 Nucl. Fusion 62 076032）中动力学模型得到的模拟结果。这表明核心-边缘组合模型和人工机制都能够模拟波的传播和吸收。
{"title":"Interaction between the core and the edge for ion cyclotron resonance heating based on artificial absorption plasma model","authors":"Zhuoqi Liu, Jiahui Zhang, Kaibang Wu, Xinjun Zhang, Chengming Qin, Feng Wang, Zhengxiong Wang","doi":"10.1088/2058-6272/ad60f5","DOIUrl":"https://doi.org/10.1088/2058-6272/ad60f5","url":null,"abstract":"\u0000 In numerical simulations of the ion cyclotron range of frequencies (ICRF) wave heating scheme, core solvers usually focus on wave propagation and absorption mechanisms within the core plasma region. However, the realistic scrape-off layer (SOL) plasma is usually simplified, making it difficult to have deeper understanding of wave propagation and absorption within the SOL. In this work, we employ a cold plasma assumption and an artificial absorption mechanism based on the approach of reference (Zhang et al 2022 Nucl. Fusion 62 076032), to study wave propagation and absorption in the realistic SOL plasma of the EAST. During the exponential decay of the total coupled power with respect to the toroidal mode numbers, several fluctuations are observed in the case of low collisional frequencies. The fluctuations may be caused by the cavity modes associated with specific toroidal mode numbers. Due to the presence of cutoff densities, the edge power losses and the total coupled power exhibit different behaviors before and after the cut-off layer is “open”. Furthermore, the simulation results obtained from the kinetic model in reference (Zhang et al 2022 Nucl. Fusion 62 076032) is discussed. This suggests that both the core-edge combined model and the artificial mechanism are capable of simulating wave propagation and absorption.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"61 18","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141663059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-06DOI: 10.1088/2058-6272/ad5fe6
Wenhao Zhou, Dongxuan Zhang, Xiaohui Duan, Xi Zhu, Feng Liu, Z. Fang
Dielectric barrier discharge (DBD) is considered as a promising technique to produce large volume uniform plasma at atmospheric pressure, and the dielectric barrier layer between the electrodes plays a key role in the DBD processes and enhancing discharge uniformity. In this work, the uniformity and discharge characteristics of the nanosecond (ns) pulsed DBD with dielectric barrier layers made of alumina, quartz glass, polycarbonate (PC), and polypropylene (PP) are investigated via discharge image observation, voltage-current waveform measurement and optical emission spectral diagnosis. Through analyzing discharge image by gray value standard deviation method, the discharge uniformity is quantitatively calculated. The effects of the space electric field intensity, the electron density (Ne), and the space reactive species on the uniformity are studied with quantifying the gap voltage Ug and the discharge current Ig, analyzing the recorded optical emission spectra, and simulating the temporal distribution of Ne with a one-dimensional fluid model. It is found that as the relative permittivity of the dielectric materials increases, the space electric field intensity is enhanced, which results in a higher Ne and electron temperature (Te). Therefore, an appropriate value of space electric field intensity can promote electron avalanches, resulting in uniform and stable plasma by the merging of electron avalanches. However, an excessive value of space electric field intensity leads to the aggregation of space charges and the distortion of the space electric field, which reduce the discharge uniformity. The surface roughness and the surface charge decay are measured to explain the influences of the surface properties and the second electron emission on the discharge uniformity. The results in this work give a comprehensive understanding of the effect of the dielectric materials on the DBD uniformity, and contribute to the selection of dielectric materials for DBD reactor and the realization of atmospheric pressure uniform, stable, and reactive plasma sources.
介质阻挡放电（DBD）被认为是在大气压力下产生大体积均匀等离子体的一种有前途的技术，而电极之间的介质阻挡层在 DBD 过程和提高放电均匀性中起着关键作用。本研究通过放电图像观察、电压电流波形测量和光发射光谱诊断，研究了使用氧化铝、石英玻璃、聚碳酸酯（PC）和聚丙烯（PP）介质阻挡层的纳秒（ns）脉冲 DBD 的均匀性和放电特性。通过灰度值标准偏差法分析放电图像，定量计算放电均匀性。通过量化间隙电压 Ug 和放电电流 Ig、分析记录的光发射光谱以及用一维流体模型模拟 Ne 的时间分布，研究了空间电场强度、电子密度 (Ne) 和空间活性物种对均匀性的影响。研究发现，随着介电材料相对介电常数的增加，空间电场强度会增强，从而导致更高的 Ne 和电子温度 (Te)。因此，适当的空间电场强度值可以促进电子雪崩，通过电子雪崩的合并形成均匀稳定的等离子体。然而，过大的空间电场强度值会导致空间电荷聚集和空间电场扭曲，从而降低放电均匀性。通过测量表面粗糙度和表面电荷衰减来解释表面特性和二次电子发射对放电均匀性的影响。这项工作的结果使人们全面了解了介电材料对 DBD 均匀性的影响，有助于为 DBD 反应器选择介电材料和实现常压均匀、稳定和反应性等离子体源。
{"title":"Effect of dielectric material on the uniformity of nanosecond pulsed dielectric barrier discharge","authors":"Wenhao Zhou, Dongxuan Zhang, Xiaohui Duan, Xi Zhu, Feng Liu, Z. Fang","doi":"10.1088/2058-6272/ad5fe6","DOIUrl":"https://doi.org/10.1088/2058-6272/ad5fe6","url":null,"abstract":"\u0000 Dielectric barrier discharge (DBD) is considered as a promising technique to produce large volume uniform plasma at atmospheric pressure, and the dielectric barrier layer between the electrodes plays a key role in the DBD processes and enhancing discharge uniformity. In this work, the uniformity and discharge characteristics of the nanosecond (ns) pulsed DBD with dielectric barrier layers made of alumina, quartz glass, polycarbonate (PC), and polypropylene (PP) are investigated via discharge image observation, voltage-current waveform measurement and optical emission spectral diagnosis. Through analyzing discharge image by gray value standard deviation method, the discharge uniformity is quantitatively calculated. The effects of the space electric field intensity, the electron density (Ne), and the space reactive species on the uniformity are studied with quantifying the gap voltage Ug and the discharge current Ig, analyzing the recorded optical emission spectra, and simulating the temporal distribution of Ne with a one-dimensional fluid model. It is found that as the relative permittivity of the dielectric materials increases, the space electric field intensity is enhanced, which results in a higher Ne and electron temperature (Te). Therefore, an appropriate value of space electric field intensity can promote electron avalanches, resulting in uniform and stable plasma by the merging of electron avalanches. However, an excessive value of space electric field intensity leads to the aggregation of space charges and the distortion of the space electric field, which reduce the discharge uniformity. The surface roughness and the surface charge decay are measured to explain the influences of the surface properties and the second electron emission on the discharge uniformity. The results in this work give a comprehensive understanding of the effect of the dielectric materials on the DBD uniformity, and contribute to the selection of dielectric materials for DBD reactor and the realization of atmospheric pressure uniform, stable, and reactive plasma sources.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":" 32","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141672645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-06DOI: 10.1088/2058-6272/ad5fe5
A. Ponomarenko, A. Yashin, V. Gusev, E. Kiselev, G. Kurskiev, V. Minaev, Y. Petrov, N. Sakharov, P. Shchegolev, E. Tkachenko, N. Zhiltsov
The first results of investigation of the turbulence structure using Doppler backscattering (DBS) on the Globus-M2 tokamak are presented. A one-channel DBS system with a variable probing frequency within the 18-26 GHz range was installed to investigate the edge plasma at normalized minor radii ρ = 0.9 – 1.1. Radial correlation Doppler reflectometry was used to study the changes in turbulence eddies after the LH transition. Correlation analysis was applied to the phase derivative of complex IQ signals of the DBS diagnostic as it contains information about the poloidal plasma rotation velocity. In L-mode the radial correlation length Lr is estimated to be 3 cm and after transition to H-mode reduces to approximately 2 cm. Gyrokinetic modelling in a linear local approximation using code GENE indicates that the instability with positive growth rates at the normalized minor radius ρ = 0.75 in L-mode and H-mode on Globus-M2 was the ion temperature gradient (ITG) mode.
本文介绍了利用多普勒反向散射（DBS）对 Globus-M2 托卡马克的湍流结构进行研究的首批结果。安装了一个在 18-26 GHz 范围内探测频率可变的单通道 DBS 系统，用于研究归一化小半径 ρ = 0.9 - 1.1 的边缘等离子体。径向相关多普勒反射仪用于研究 LH 转变后湍流涡的变化。相关分析被应用于 DBS 诊断的复 IQ 信号的相位导数，因为它包含了极性等离子体旋转速度的信息。在 L 模式下，径向相关长度 Lr 估计为 3 厘米，过渡到 H 模式后则减小到约 2 厘米。利用代码 GENE 进行线性局部近似的陀螺动力学建模表明，在 Globus-M2 上的 L 模式和 H 模式中，归一化小半径 ρ = 0.75 处增长率为正的不稳定性是离子温度梯度（ITG）模式。
{"title":"First results of turbulence investigation on Globus-M2 using radial correlation Doppler reflectometry","authors":"A. Ponomarenko, A. Yashin, V. Gusev, E. Kiselev, G. Kurskiev, V. Minaev, Y. Petrov, N. Sakharov, P. Shchegolev, E. Tkachenko, N. Zhiltsov","doi":"10.1088/2058-6272/ad5fe5","DOIUrl":"https://doi.org/10.1088/2058-6272/ad5fe5","url":null,"abstract":"\u0000 The first results of investigation of the turbulence structure using Doppler backscattering (DBS) on the Globus-M2 tokamak are presented. A one-channel DBS system with a variable probing frequency within the 18-26 GHz range was installed to investigate the edge plasma at normalized minor radii ρ = 0.9 – 1.1. Radial correlation Doppler reflectometry was used to study the changes in turbulence eddies after the LH transition. Correlation analysis was applied to the phase derivative of complex IQ signals of the DBS diagnostic as it contains information about the poloidal plasma rotation velocity. In L-mode the radial correlation length Lr is estimated to be 3 cm and after transition to H-mode reduces to approximately 2 cm. Gyrokinetic modelling in a linear local approximation using code GENE indicates that the instability with positive growth rates at the normalized minor radius ρ = 0.75 in L-mode and H-mode on Globus-M2 was the ion temperature gradient (ITG) mode.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":" 15","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141671747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-05DOI: 10.1088/2058-6272/ad5fe3
Siyin Zhou, Xiang Liu, Wansheng Nie, Shuhui Yuan
To optimize the design of plasma injectors, the influence of different external electrodes on plasma-assisted flame stabilization was assessed by using a nonequilibrium plasma injector flame control setup. The electrical characteristics of the injector, flame structure parameters, flame intensity, discharge power, and cost-to-effectiveness ratio under different external electrodes (four mesh electrodes and one copper foil electrode) were analyzed using electrical and optical methods. The results show that reducing the mesh size of the external electrode leads to a decrease in breakdown voltage. Compared with a ceramic dielectric barrier-based injector, an injector with a quartz dielectric barrier produces a higher breakdown voltage under the same conditions. For the same actuation voltage, the discharge current increases as the mesh size of the external electrode decreases, and combustion is enhanced by the discharge plasma; therefore, it is better to adopt a smaller mesh hole size to realize good flame stabilization under a lower actuation voltage. However, under the studied working conditions, reducing the mesh hole size of the external electrode increases the cost-to-effectiveness ratio of plasma injector-based flame stabilization. Thus, considering the cost-to-effectiveness ratio and the weight of the injector, an external electrode with a larger mesh hole size should be chosen, which contradicts the above rule.
{"title":"Comparison of the effect of different external electrodes on discharge plasma-assisted diffusion flame stabilization","authors":"Siyin Zhou, Xiang Liu, Wansheng Nie, Shuhui Yuan","doi":"10.1088/2058-6272/ad5fe3","DOIUrl":"https://doi.org/10.1088/2058-6272/ad5fe3","url":null,"abstract":"\u0000 To optimize the design of plasma injectors, the influence of different external electrodes on plasma-assisted flame stabilization was assessed by using a nonequilibrium plasma injector flame control setup. The electrical characteristics of the injector, flame structure parameters, flame intensity, discharge power, and cost-to-effectiveness ratio under different external electrodes (four mesh electrodes and one copper foil electrode) were analyzed using electrical and optical methods. The results show that reducing the mesh size of the external electrode leads to a decrease in breakdown voltage. Compared with a ceramic dielectric barrier-based injector, an injector with a quartz dielectric barrier produces a higher breakdown voltage under the same conditions. For the same actuation voltage, the discharge current increases as the mesh size of the external electrode decreases, and combustion is enhanced by the discharge plasma; therefore, it is better to adopt a smaller mesh hole size to realize good flame stabilization under a lower actuation voltage. However, under the studied working conditions, reducing the mesh hole size of the external electrode increases the cost-to-effectiveness ratio of plasma injector-based flame stabilization. Thus, considering the cost-to-effectiveness ratio and the weight of the injector, an external electrode with a larger mesh hole size should be chosen, which contradicts the above rule.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":" 20","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141676956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-03DOI: 10.1088/2058-6272/ad5ec2
Muhammad Saqib Akhtar, Mhedine Alicherif, Bing Wang, D. Lacoste
This study investigates the effect of a rotating gliding discharge on synthetic biogas combustion at atmospheric pressure. Synthetic biogas was produced by mixing methane and carbon dioxide. Three mixtures were considered: 100%-0%, 70%-30%, and 50%-50% of methane and carbon dioxide, respectively. The plasma effect was investigated in a low-swirl-number burner equipped with a high-voltage electrode to produce gliding discharges. The effect of plasma on the stability limits of the flame is reported for several electrical powers. During plasma-assisted combustion, the lean blow-off limits of biogas-air flames were significantly improved, which agrees with what can be found in the literature for other fuels. The electrical parameters of the discharge and the plasma emissions were measured using electric probes and emission spectroscopy, respectively. The mixture with the CO2 dilution was associated with a higher reduced electric field and higher ion production. A better understanding of the excited-species concentration evolution during plasma is necessary and will be investigated in future work.
{"title":"Effect of rotating gliding discharges on the lean blow-off limit of biogas flames","authors":"Muhammad Saqib Akhtar, Mhedine Alicherif, Bing Wang, D. Lacoste","doi":"10.1088/2058-6272/ad5ec2","DOIUrl":"https://doi.org/10.1088/2058-6272/ad5ec2","url":null,"abstract":"\u0000 This study investigates the effect of a rotating gliding discharge on synthetic biogas combustion at atmospheric pressure. Synthetic biogas was produced by mixing methane and carbon dioxide. Three mixtures were considered: 100%-0%, 70%-30%, and 50%-50% of methane and carbon dioxide, respectively. The plasma effect was investigated in a low-swirl-number burner equipped with a high-voltage electrode to produce gliding discharges. The effect of plasma on the stability limits of the flame is reported for several electrical powers. During plasma-assisted combustion, the lean blow-off limits of biogas-air flames were significantly improved, which agrees with what can be found in the literature for other fuels. The electrical parameters of the discharge and the plasma emissions were measured using electric probes and emission spectroscopy, respectively. The mixture with the CO2 dilution was associated with a higher reduced electric field and higher ion production. A better understanding of the excited-species concentration evolution during plasma is necessary and will be investigated in future work.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"72 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141682369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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