Pub Date : 2024-04-18DOI: 10.1088/1741-4326/ad4046
Guiding Wang, T. L. Rhodes, Q. Pratt, William A Peebles, Neal A Crocker, Rongjie Hong, M. E. Austin, M. V. Van Zeeland, Sterling P Smith
Sawteeth are one of the concerning instabilities in ITER and future burning plasma experiments. Sawtooth dynamics and its interaction with broadband plasma turbulence has been a challenge for predictive simulations of core transport in future fusion devices. This study provides new observations of core turbulence behavior during sawtooth oscillations in DIII-D hydrogen L-mode neutral beam injection heated plasmas in an inner wall limited configuration. A strong correlation of electron temperature and density turbulence levels with the sawtooth oscillation phase has been observed at locations inside the Te inversion radius and/or safety factor q=1 magnetic surface. The Te turbulence amplitude in the core during the sawtooth ramp exhibits a critical Te gradient behavior inside but not near the Te inversion radius/q=1 magnetic surface. The most unstable mode calculated from the trapped gyro-landau fluid (TGLF) turbulence simulations reveal a change from low-k ion-type to low-k electron-type modes from pre- to post- sawtooth crash time periods.
锯齿是国际热核聚变实验堆和未来燃烧等离子体实验中令人担忧的不稳定性之一。锯齿动力学及其与宽带等离子体湍流的相互作用一直是未来聚变装置中堆芯传输预测模拟的挑战。本研究提供了在内壁受限配置的 DIII-D 氢 L 模式中性束注入加热等离子体锯齿振荡过程中内核湍流行为的新观测结果。在Te反演半径和/或安全系数q=1磁面内的位置，观察到电子温度和密度湍流水平与锯齿振荡相位有很强的相关性。在锯齿斜坡期间，核心中的Te湍流振幅在Te反转半径/q=1磁面内部表现出临界Te梯度行为，而在Te反转半径/q=1磁面附近则没有。根据受困陀螺-朗道流体（TGLF）湍流模拟计算得出的最不稳定模式显示，从锯齿撞击前到锯齿撞击后的时间段内，低k离子型模式转变为低k电子型模式。
{"title":"Core electron temperature turbulence and transport during sawtooth oscillations in the DIII-D tokamak","authors":"Guiding Wang, T. L. Rhodes, Q. Pratt, William A Peebles, Neal A Crocker, Rongjie Hong, M. E. Austin, M. V. Van Zeeland, Sterling P Smith","doi":"10.1088/1741-4326/ad4046","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4046","url":null,"abstract":"\u0000 Sawteeth are one of the concerning instabilities in ITER and future burning plasma experiments. Sawtooth dynamics and its interaction with broadband plasma turbulence has been a challenge for predictive simulations of core transport in future fusion devices. This study provides new observations of core turbulence behavior during sawtooth oscillations in DIII-D hydrogen L-mode neutral beam injection heated plasmas in an inner wall limited configuration. A strong correlation of electron temperature and density turbulence levels with the sawtooth oscillation phase has been observed at locations inside the Te inversion radius and/or safety factor q=1 magnetic surface. The Te turbulence amplitude in the core during the sawtooth ramp exhibits a critical Te gradient behavior inside but not near the Te inversion radius/q=1 magnetic surface. The most unstable mode calculated from the trapped gyro-landau fluid (TGLF) turbulence simulations reveal a change from low-k ion-type to low-k electron-type modes from pre- to post- sawtooth crash time periods.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":" 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140686878","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 : 2024-04-18DOI: 10.1088/1741-4326/ad4047
K. McCarthy, I. García-Cortés, Arturo Alonso, Ana Arias-Camisón, E. Ascasíbar, A. Baciero, A. Cappa, Ricardo Carrasco, O. Chmyga, Teresa Estrada, Raul García, J. Hernández Sánchez, Francisco Javier Hernanz, O. Kozachok, Belén López-Miranda, F. Medina, Daniel Medina Roque, B. V. Van Milligen, Miguel Navarro, M. Ochando, J. D. de Pablos, N. Panadero, Ignacio Pastor, Jaime de la Riva Villen, Ma. Carmen Rodriguez Fernandez, D. Tafalla, V. Tribaldos
A pellet-induced enhanced confinement (PiEC) phase, with general characteristics similar to those reported for the stellarator W7-X, is observed after single pellet injection (>1019 H atoms) into the neutral beam injection heated phase of plasmas in the mid-sized heliac-type stellarator TJ-II. In addition to a step-like increase in density, plasma diamagnetic energy content rises significantly with respect to that of reference discharges, energy confinement time is similarly enhanced when compared to International Stellarator Scaling law predictions (H. Yamada et al., Nucl. Fusion 45 (2005) 1684) renormalized for TJ-II, and the triple product, ne · Ti · E, exhibits a clear bifurcation towards an improved confinement branch when compared to the branch product predicted by the same law. In this work, multiple pellets are injected in series into NBI-heated plasmas in the TJ-II and post-injection plasma performance is reported and discussed. For instance, a charge-exchange recombination spectroscopy diagnostic reveals significantly increased core ion temperatures after pellet injection compared to temperatures achieved in comparable reference plasmas, this pointing to increased ion energy content and improved ion energy confinement during a PiEC phase. It is also found that enhanced performance is independent of whether co- or counter-NBI heating beam is employed. Finally, record stored diamagnetic energy content and plasma beta values are achieved when the largest available pellets are employed. The results indicate that pellet injections extend the operational regime well beyond limits previously achieved in TJ-II without pellets.
{"title":"Multi-pellet injection into the NBI-heated phase of TJ-II plasmas","authors":"K. McCarthy, I. García-Cortés, Arturo Alonso, Ana Arias-Camisón, E. Ascasíbar, A. Baciero, A. Cappa, Ricardo Carrasco, O. Chmyga, Teresa Estrada, Raul García, J. Hernández Sánchez, Francisco Javier Hernanz, O. Kozachok, Belén López-Miranda, F. Medina, Daniel Medina Roque, B. V. Van Milligen, Miguel Navarro, M. Ochando, J. D. de Pablos, N. Panadero, Ignacio Pastor, Jaime de la Riva Villen, Ma. Carmen Rodriguez Fernandez, D. Tafalla, V. Tribaldos","doi":"10.1088/1741-4326/ad4047","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4047","url":null,"abstract":"\u0000 A pellet-induced enhanced confinement (PiEC) phase, with general characteristics similar to those reported for the stellarator W7-X, is observed after single pellet injection (>1019 H atoms) into the neutral beam injection heated phase of plasmas in the mid-sized heliac-type stellarator TJ-II. In addition to a step-like increase in density, plasma diamagnetic energy content rises significantly with respect to that of reference discharges, energy confinement time is similarly enhanced when compared to International Stellarator Scaling law predictions (H. Yamada et al., Nucl. Fusion 45 (2005) 1684) renormalized for TJ-II, and the triple product, ne · Ti · E, exhibits a clear bifurcation towards an improved confinement branch when compared to the branch product predicted by the same law. In this work, multiple pellets are injected in series into NBI-heated plasmas in the TJ-II and post-injection plasma performance is reported and discussed. For instance, a charge-exchange recombination spectroscopy diagnostic reveals significantly increased core ion temperatures after pellet injection compared to temperatures achieved in comparable reference plasmas, this pointing to increased ion energy content and improved ion energy confinement during a PiEC phase. It is also found that enhanced performance is independent of whether co- or counter-NBI heating beam is employed. Finally, record stored diamagnetic energy content and plasma beta values are achieved when the largest available pellets are employed. The results indicate that pellet injections extend the operational regime well beyond limits previously achieved in TJ-II without pellets.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":" 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140685975","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 : 2024-04-18DOI: 10.1088/1741-4326/ad4048
Lunan Liu, Xinjun Zhang, Chengming Qin, Y. Mao, Shuai Yuan, Wei Zhang, Hua Yang, Lei Wang, Yan Cheng, Kai Zhang
Ion cyclotron resonance heating (ICRH) has been a dependable tool for sturdy plasma heating with high RF power of several megawatts. However, a sudden increase in the reflected power during ICRH heating experiments is a problem that should be solved for future fusion experimental devices. To solve this issue, the load tolerant matching network have been designed for ICRH system in EAST Tokamak. The matching network includes 3-stub tuner impedance matching system, conjugate-T structure, 30 Ω to 50 Ω transmission line and center grounded antenna strap. By keeping a low reflection ratio in the network for a wide range of resistance, this matching network could allow sturdy high-power operations without fast impedance matching in EAST tokamak. In our matching network, the two arms of a conjugate-T were designed to have λ/2 length difference which could mitigate current imbalance and antenna poloidal phasing out of control problem. And the T-point corresponds to the maximum point of standing wave voltage, which could greatly improve the input impedance of antenna.
离子回旋共振加热（ICRH）一直是利用几兆瓦高射频功率进行坚固等离子体加热的可靠工具。然而，ICRH 加热实验中反射功率的突然增加是未来核聚变实验设备需要解决的一个问题。为了解决这个问题，我们为 EAST 托卡马克中的 ICRH 系统设计了耐负载匹配网络。该匹配网络包括 3 桩调谐器阻抗匹配系统、共轭 T 结构、30 Ω 至 50 Ω 传输线和中心接地天线带。通过在宽电阻范围内保持网络的低反射比，该匹配网络可以在 EAST 托卡马克中实现坚固的大功率运行，而无需快速阻抗匹配。在我们的匹配网络中，共轭 T 的两臂被设计为具有 λ/2 长度差，这可以缓解电流不平衡和天线极性相位失控问题。而且 T 点对应驻波电压的最大点，可以大大改善天线的输入阻抗。
{"title":"Design and operations of a load-tolerant ICRH system in Experimental Advanced Superconducting Tokamak","authors":"Lunan Liu, Xinjun Zhang, Chengming Qin, Y. Mao, Shuai Yuan, Wei Zhang, Hua Yang, Lei Wang, Yan Cheng, Kai Zhang","doi":"10.1088/1741-4326/ad4048","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4048","url":null,"abstract":"\u0000 Ion cyclotron resonance heating (ICRH) has been a dependable tool for sturdy plasma heating with high RF power of several megawatts. However, a sudden increase in the reflected power during ICRH heating experiments is a problem that should be solved for future fusion experimental devices. To solve this issue, the load tolerant matching network have been designed for ICRH system in EAST Tokamak. The matching network includes 3-stub tuner impedance matching system, conjugate-T structure, 30 Ω to 50 Ω transmission line and center grounded antenna strap. By keeping a low reflection ratio in the network for a wide range of resistance, this matching network could allow sturdy high-power operations without fast impedance matching in EAST tokamak. In our matching network, the two arms of a conjugate-T were designed to have λ/2 length difference which could mitigate current imbalance and antenna poloidal phasing out of control problem. And the T-point corresponds to the maximum point of standing wave voltage, which could greatly improve the input impedance of antenna.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":" 38","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140689266","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 : 2024-04-17DOI: 10.1088/1741-4326/ad3fca
V. Zamkovska, S. Sabbagh, Matthew Tobin, J. Berkery, J. Riquezes, Young-Seok Park, Keith Erickson, Jalal Butt, J. Bak, Jayhyun Kim, Kyu-Dong Lee, Jinseok Ko, Si-Woo Yoon, C. Ham, Lucy Kogan
Abnormal (deviating from target) variations in the plasma vertical position Z and current Ip (such as vertical displacements, transient Ip 'spikes' and quenches) constitute common elements of a disruption, a phenomenon that is to be mitigated, or ultimately avoided in future reactor-relevant tokamaks. While those abnormalities are generally recognized cross-shot and cross-device, details in terms of appearance (or not) and order of those abnormalities in disruption event chains is bound with the plasma state at the time of the chain initiation. Detection of those abnormalities is thus indicative not only of the onset of the plasma collapse itself, but also of the disruption driving cause that is promoted at the particular plasma state. Here, occurrence of disruptions, explored via detection of a Ip quench, and analysis of disruption event chains constituted by Ip and Z abnormalities, is reported for in total 7 full years of operation of 3 devices (KSTAR, MAST-U and NSTX-U) using the DECAFTM code expanded tools and capabilities. It is shown that the disruption occurrence depends not only on details of the plasma state, but also on (device-dependent) technical elements of the shot exit scenario. A year-to-year change in main disruption causes and a reduction of the disruptivity rate, bound with device and operation upgrades, are reported. Particular trigger instances of disruption event chains (and the full chains, when applicable) are shown to occupy different parts of the operation space diagrams, in accordance with prior expectation. Plasma elongation is identified as an important factor influencing details of the chains and its role will be further explored.
等离子体垂直位置 Z 和电流 Ip 的异常（偏离目标）变化（如垂直位移、瞬时 Ip "尖峰 "和淬火）构成了扰乱的共同要素，这种现象在未来与反应堆相关的托卡马克中需要减轻或最终避免。虽然这些异常现象通常可以通过跨射程和跨设备识别，但这些异常现象在中断事件链中出现（或不出现）的细节和顺序与中断事件链开始时的等离子体状态有关。因此，对这些异常的检测不仅表明等离子体坍缩本身的发生，而且表明在特定等离子体状态下产生破坏的驱动原因。在此，利用 DECAFTM 代码的扩展工具和功能，对 3 个装置（KSTAR、MAST-U 和 NSTX-U）总共 7 年的运行情况进行了报告。结果表明，中断的发生不仅取决于等离子体状态的细节，还取决于（与设备有关的）射出场景的技术要素。报告显示，随着设备和操作的升级，主要中断原因逐年发生变化，中断率也随之降低。根据之前的预期，中断事件链（以及完整的中断事件链）的特定触发实例占据了运行空间图的不同部分。等离子体伸长率被确定为影响链细节的一个重要因素，其作用将得到进一步探讨。
{"title":"DECAF Cross-device characterization of tokamak disruptions indicated by abnormalities in plasma vertical position and current","authors":"V. Zamkovska, S. Sabbagh, Matthew Tobin, J. Berkery, J. Riquezes, Young-Seok Park, Keith Erickson, Jalal Butt, J. Bak, Jayhyun Kim, Kyu-Dong Lee, Jinseok Ko, Si-Woo Yoon, C. Ham, Lucy Kogan","doi":"10.1088/1741-4326/ad3fca","DOIUrl":"https://doi.org/10.1088/1741-4326/ad3fca","url":null,"abstract":"\u0000 Abnormal (deviating from target) variations in the plasma vertical position Z and current Ip (such as vertical displacements, transient Ip 'spikes' and quenches) constitute common elements of a disruption, a phenomenon that is to be mitigated, or ultimately avoided in future reactor-relevant tokamaks. While those abnormalities are generally recognized cross-shot and cross-device, details in terms of appearance (or not) and order of those abnormalities in disruption event chains is bound with the plasma state at the time of the chain initiation. Detection of those abnormalities is thus indicative not only of the onset of the plasma collapse itself, but also of the disruption driving cause that is promoted at the particular plasma state. Here, occurrence of disruptions, explored via detection of a Ip quench, and analysis of disruption event chains constituted by Ip and Z abnormalities, is reported for in total 7 full years of operation of 3 devices (KSTAR, MAST-U and NSTX-U) using the DECAFTM code expanded tools and capabilities. It is shown that the disruption occurrence depends not only on details of the plasma state, but also on (device-dependent) technical elements of the shot exit scenario. A year-to-year change in main disruption causes and a reduction of the disruptivity rate, bound with device and operation upgrades, are reported. Particular trigger instances of disruption event chains (and the full chains, when applicable) are shown to occupy different parts of the operation space diagrams, in accordance with prior expectation. Plasma elongation is identified as an important factor influencing details of the chains and its role will be further explored.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":" 40","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140691330","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}
Fuel magnetization significantly lowers the required radial convergence enabling cylindrical implosions to become an promising approach for inertial confinement fusion (ICF). Nernst effect on the two-layer single shell magnetized target design applied to Z-pinch benefits from a gold layer that decreases fuel demagnetization and serves as a magnetothermal insulation layer, preventing magnetothermal losses. The resistive diffusion and Nernst advection of the magnetic field are considered in the radiation magnetohydrodynamic (RMHD) model, which alter the evolution of magnetic flux in the magnetized target and result in plasma demagnetization. The results demonstrate that targets with a wide range of parameters can achieve ignition condition under a 30 MA driven current. A two-layer single shell magnetized target for lessening the Nernst effect has the potential to achieve ignition condition. The fusion yield of the optimal target increases by 168% from 0.71 MJ to 1.90 MJ, compared to a one-layer single shell target.
{"title":"A two-layer single shell magnetized target for lessening the Nernst effect","authors":"Shijia Chen, Fuyuan Wu, Hua Zhang, Cangtao Zhou, Yan-Yun Ma, Rafael Ramis","doi":"10.1088/1741-4326/ad3fcc","DOIUrl":"https://doi.org/10.1088/1741-4326/ad3fcc","url":null,"abstract":"\u0000 Fuel magnetization significantly lowers the required radial convergence enabling cylindrical implosions to become an promising approach for inertial confinement fusion (ICF). Nernst effect on the two-layer single shell magnetized target design applied to Z-pinch benefits from a gold layer that decreases fuel demagnetization and serves as a magnetothermal insulation layer, preventing magnetothermal losses. The resistive diffusion and Nernst advection of the magnetic field are considered in the radiation magnetohydrodynamic (RMHD) model, which alter the evolution of magnetic flux in the magnetized target and result in plasma demagnetization. The results demonstrate that targets with a wide range of parameters can achieve ignition condition under a 30 MA driven current. A two-layer single shell magnetized target for lessening the Nernst effect has the potential to achieve ignition condition. The fusion yield of the optimal target increases by 168% from 0.71 MJ to 1.90 MJ, compared to a one-layer single shell target.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":" 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140692547","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 : 2024-04-17DOI: 10.1088/1741-4326/ad3fcd
L. Piron, C. Paz-Soldan, L. Pigatto, P. Zanca, Olivier Sauter, T. Pütterich, Paolo Bettini, M. Bonotto, Geoffrey Cunningham, Gianmaria De Tommasi, Nicolò Ferron, Matteo Gambrioli, Georgina Graham, Peter C de Vries, Y. Gribov, Q. Hu, K. Kirov, N. Logan, Morten Lennholm, Massimiliano Mattei, Marc Maraschek, Tomas Markovic, G. Manduchi, Piero Martin, A. Pironti, A. Polevoi, T. Ravensbergen, David Anthony Ryan, B. Sieglin, W. Suttrop, D. Terranova, M. Teschke, Daniel F. Valcarcel, Charles Vincent
In magnetic fusion devices, error field sources, spurious magnetic field perturbations, need to be identified and corrected for safe and stable (disruption-free) tokamak operation. Within Work Package Tokamak Exploitation RT04, a series of studies have been carried out to test the portability of the novel non-disruptive method, designed and tested in DIII-D (Paz-Soldan C. et al, Nuclear Fusion 62 (2022) 126007), and to perform an assessment of model-based EF control strategies towards their applicability in ITER. In this paper, the lessons learned, the physical mechanism behind the magnetic island healing, which relies on enhanced viscous torque that acts against the static electro-magnetic torque, and the main control achievements are reported, together with the first design of the asynchronous EF correction current/density controller for ITER.
在磁核聚变装置中，需要识别和纠正错误磁场源、虚假磁场扰动，以实现托卡马克的安全稳定（无干扰）运行。在托卡马克开发 RT04 工作包中，开展了一系列研究，以测试在 DIII-D 中设计和测试的新型无干扰方法的可移植性（Paz-Soldan C. 等人，核聚变 62 (2022) 126007），并对基于模型的 EF 控制策略进行评估，以确定其在热核聚变实验堆中的适用性。本文报告了汲取的经验教训、磁岛愈合背后的物理机制（依靠增强的粘性力矩对抗静态电磁力矩）和主要控制成果，以及用于热核实验堆的异步外频修正电流/密度控制器的首次设计。
{"title":"Error field detection and correction studies towards ITER operation","authors":"L. Piron, C. Paz-Soldan, L. Pigatto, P. Zanca, Olivier Sauter, T. Pütterich, Paolo Bettini, M. Bonotto, Geoffrey Cunningham, Gianmaria De Tommasi, Nicolò Ferron, Matteo Gambrioli, Georgina Graham, Peter C de Vries, Y. Gribov, Q. Hu, K. Kirov, N. Logan, Morten Lennholm, Massimiliano Mattei, Marc Maraschek, Tomas Markovic, G. Manduchi, Piero Martin, A. Pironti, A. Polevoi, T. Ravensbergen, David Anthony Ryan, B. Sieglin, W. Suttrop, D. Terranova, M. Teschke, Daniel F. Valcarcel, Charles Vincent","doi":"10.1088/1741-4326/ad3fcd","DOIUrl":"https://doi.org/10.1088/1741-4326/ad3fcd","url":null,"abstract":"\u0000 In magnetic fusion devices, error field sources, spurious magnetic field perturbations, need to be identified and corrected for safe and stable (disruption-free) tokamak operation. Within Work Package Tokamak Exploitation RT04, a series of studies have been carried out to test the portability of the novel non-disruptive method, designed and tested in DIII-D (Paz-Soldan C. et al, Nuclear Fusion 62 (2022) 126007), and to perform an assessment of model-based EF control strategies towards their applicability in ITER. In this paper, the lessons learned, the physical mechanism behind the magnetic island healing, which relies on enhanced viscous torque that acts against the static electro-magnetic torque, and the main control achievements are reported, together with the first design of the asynchronous EF correction current/density controller for ITER.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"119 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140693567","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 : 2024-04-16DOI: 10.1088/1741-4326/ad3f2f
Donguk Kim, Sangjin Park, G. Choi, Y. W. Cho, Jisung Kang, Hyunsun Han, Jeff Candy, E. Belli, Y. Na, T. Hahm, C. Sung
Further investigation of fast ion effects on turbulence and transport in the FIRE mode discharge [H. Han et al, Nature 609 269–275 (2022)] was performed in this work as a continuation of a previous study [D. Kim et al Nucl. Fusion 63 124001 (2023)] that showed that the dominant turbulence suppression mechanism by fast ions is the dilution effect in the FIRE mode discharge. The current study includes (i) the impact of the fast ion relevant mode observed in the simulation of thermal energy flux, (ii) dilution effects by fast ions compared to dilution effects by other species, and (iii) fast ion effects on electron-scale turbulence. First, nonlinear gyrokinetic simulation results show that turbulence is significantly suppressed even without the fast ion relevant mode, indicating that the impact of this mode on thermal transport is not significant in this discharge. Second, further analysis on the dilution effects shows the three following results: Turbulence is not completely suppressed by the reduced main ion density fraction effect due to impurities; the reduction in energy flux can be limited by a certain impurity mode that is destabilized by a high impurity density gradient from adjusting the main ion density gradient; electrons can contribute to turbulence suppression through the main ion density gradient change, although this effect is less significant compared to other species. Third, we observe that two fast ion effects can influence the linear growth rate of the electron-scale turbulence mode. The growth rate decreases by an increase in β*(≡(-8π/B2)dp/dr) and increases by dilution effects, suggesting that fast ion effects on electron-scale turbulence can differ depending on the operation scenario, such as the fast ion fraction. The comprehensive analysis performed in this study can enhance our understanding of fast ion physics, required for burning plasma operation in the future.
在这项工作中，作为先前研究[D. Kim 等，Nucl. Fusion 63 124001 (2023)]的延续，进一步研究了快离子对 FIRE 模式放电中的湍流和传输的影响[H. Han 等，Nature 609 269-275 (2022)]，该研究表明快离子的主要湍流抑制机制是 FIRE 模式放电中的稀释效应。目前的研究包括：(i) 模拟热能通量时观察到的快离子相关模式的影响；(ii) 与其他物种的稀释效应相比，快离子的稀释效应；(iii) 快离子对电子尺度湍流的影响。首先，非线性陀螺动量模拟结果表明，即使没有快离子相关模式，湍流也会受到明显抑制，这表明该模式对热传输的影响在该放电中并不显著。其次，对稀释效应的进一步分析表明了以下三个结果：湍流并没有完全被杂质导致的主离子密度分数降低效应所抑制；能量通量的降低会受到某种杂质模式的限制，这种模式会因为调整主离子密度梯度而导致高杂质密度梯度不稳定；电子可以通过主离子密度梯度的变化来促进湍流的抑制，不过这种效应与其他物种相比并不显著。第三，我们观察到两种快速离子效应会影响电子尺度湍流模式的线性增长率。β*(≡(-8π/B2)dp/dr)的增加会降低增长率，而稀释效应则会提高增长率。本研究进行的综合分析可以加深我们对快离子物理的理解，这也是未来燃烧等离子体运行所需要的。
{"title":"Investigation of fast ion effects on core turbulence in FIRE mode plasmas","authors":"Donguk Kim, Sangjin Park, G. Choi, Y. W. Cho, Jisung Kang, Hyunsun Han, Jeff Candy, E. Belli, Y. Na, T. Hahm, C. Sung","doi":"10.1088/1741-4326/ad3f2f","DOIUrl":"https://doi.org/10.1088/1741-4326/ad3f2f","url":null,"abstract":"\u0000 Further investigation of fast ion effects on turbulence and transport in the FIRE mode discharge [H. Han et al, Nature\u0000 609 269–275 (2022)] was performed in this work as a continuation of a previous study [D. Kim et al Nucl. Fusion\u0000 63 124001 (2023)] that showed that the dominant turbulence suppression mechanism by fast ions is the dilution effect in the FIRE mode discharge. The current study includes (i) the impact of the fast ion relevant mode observed in the simulation of thermal energy flux, (ii) dilution effects by fast ions compared to dilution effects by other species, and (iii) fast ion effects on electron-scale turbulence. First, nonlinear gyrokinetic simulation results show that turbulence is significantly suppressed even without the fast ion relevant mode, indicating that the impact of this mode on thermal transport is not significant in this discharge. Second, further analysis on the dilution effects shows the three following results: Turbulence is not completely suppressed by the reduced main ion density fraction effect due to impurities; the reduction in energy flux can be limited by a certain impurity mode that is destabilized by a high impurity density gradient from adjusting the main ion density gradient; electrons can contribute to turbulence suppression through the main ion density gradient change, although this effect is less significant compared to other species. Third, we observe that two fast ion effects can influence the linear growth rate of the electron-scale turbulence mode. The growth rate decreases by an increase in β*(≡(-8π/B2)dp/dr) and increases by dilution effects, suggesting that fast ion effects on electron-scale turbulence can differ depending on the operation scenario, such as the fast ion fraction. The comprehensive analysis performed in this study can enhance our understanding of fast ion physics, required for burning plasma operation in the future.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"357 2‐3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140698279","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 : 2024-04-16DOI: 10.1088/1741-4326/ad3f2d
F. Kin, S. Inagaki, K. Nagasaki, M. Luo, K. Itoh, K. Shinohara, A. Terakado, T. Minami, S. Kado, Shinji Kobayashi, S. Ohshima, T. Bando, N. Oyama, M. Yoshida
The avalanche type of transport can induce a long-radial transport and thus can contribute to the global profile formation. In this study, we observed the heat perturbations exhibiting avalanche-like transport in the stellarator/heliotron device, Heliotron J, and the tokamak device, JT-60U. We found that the electron heat propagation in Heliotron J is mainly generated from the heating source region. The relatively high value of the Hurst exponent, which is a signature of avalanches, depends on the total heating power. On the other hand, the electron and ion heat avalanches measured in JT-60U tend to spread from the local peak of the temperature gradient and are not influenced by the heating source profiles. The contrasting features of avalanches in stellarator/heliotrons and tokamaks potentially imply the difference in the temperature profile formation, such as the presence of stiffness.
{"title":"Observation of avalanche-like transport in Heliotron J and JT-60U plasmas","authors":"F. Kin, S. Inagaki, K. Nagasaki, M. Luo, K. Itoh, K. Shinohara, A. Terakado, T. Minami, S. Kado, Shinji Kobayashi, S. Ohshima, T. Bando, N. Oyama, M. Yoshida","doi":"10.1088/1741-4326/ad3f2d","DOIUrl":"https://doi.org/10.1088/1741-4326/ad3f2d","url":null,"abstract":"\u0000 The avalanche type of transport can induce a long-radial transport and thus can contribute to the global profile formation. In this study, we observed the heat perturbations exhibiting avalanche-like transport in the stellarator/heliotron device, Heliotron J, and the tokamak device, JT-60U. We found that the electron heat propagation in Heliotron J is mainly generated from the heating source region. The relatively high value of the Hurst exponent, which is a signature of avalanches, depends on the total heating power. On the other hand, the electron and ion heat avalanches measured in JT-60U tend to spread from the local peak of the temperature gradient and are not influenced by the heating source profiles. The contrasting features of avalanches in stellarator/heliotrons and tokamaks potentially imply the difference in the temperature profile formation, such as the presence of stiffness.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"106 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140695168","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 : 2024-04-16DOI: 10.1088/1741-4326/ad3f30
A. Wingen, R. S. Wilcox, B. C. Lyons, L. Baylor, N. Ferraro
In ITER, pellets are calculated to require more than 8 times the mass than currently planned to reliably trigger ELMs. Unmitigated heat flux impulses from edge-localized modes (ELMs) are intolerable in ITER at full power and current. Therefore, ITER operation relies on multiple approaches to control ELM heat fluxes. One method is pellet ELM pacing to instigate small rapid ELMs with low heat flux. Predicting the performance of pellet pacing is critical for ITER, which is expected to operate in a regime with a low-collisionality, peeling-limited pedestal. However, to trigger ELMs the local pressure increase in the expanding pellet cloud pushes the equilibrium over the ballooning stability limit. In this work, linear and nonlinear M3D-C1 simulations are used to predict pellet mass thresholds in DIII-D discharges and ITER scenarios with peeling-limited pedestals. It is found that the distance of the equilibrium's operational point from the ballooning branch of the pedestal stability boundary strongly changes thresholds. Linear M3D-C1 simulations find a strong dependence of the pellet mass threshold on the poloidal injection location for ITER's 15 MA, Q=10 scenario. The required pellet mass at the planned injection locations is 8 to 17 times larger than currently considered. However, such linear simulations do not include pellet ablation physics or time evolution of density and temperature. A new scheme of 2D nonlinear simulations, coupled with linear stability analysis at various steps throughout the nonlinear time evolution, was developed to include such physics and improve on the linear results. These new nonlinear-to-linear simulations confirm previous findings. This result suggests that pellet ELM triggering in ITER could require pellets much larger than those currently planned, which makes ELM-pacing operationally challenging. On the other hand, fueling pellets injected from the high-field side will likely not unintentionally trigger ELMs in an otherwise ELM-stable plasma.
据计算，在热核实验堆中，颗粒需要比目前计划的质量大 8 倍以上，才能可靠地触发 ELM。在热核实验堆中，在全功率和全电流条件下，边缘定位模式（ELM）产生的无限制热通量脉冲是不可容忍的。因此，ITER 运行依靠多种方法来控制 ELM 热通量。其中一种方法是颗粒 ELM 起搏，以激发低热通量的小型快速 ELM。预计热核实验堆将在低碰撞、剥离受限的基底上运行，因此预测颗粒起搏的性能对于热核实验堆来说至关重要。然而，要触发 ELMs，膨胀颗粒云中的局部压力增加会将平衡推到气球稳定性极限之上。在这项工作中，使用线性和非线性 M3D-C1 模拟来预测 DIII-D 放电和具有剥离限制基座的热核实验堆方案中的颗粒质量阈值。结果发现，平衡运行点与基座稳定性边界气球分支的距离会强烈改变阈值。线性 M3D-C1 模拟发现，在 ITER 的 15 MA、Q=10 方案中，球团质量阈值与极性注入位置有很大关系。计划注入位置所需的颗粒质量比目前考虑的大 8 到 17 倍。然而，这种线性模拟不包括颗粒烧蚀物理或密度和温度的时间演变。我们开发了一种新的二维非线性模拟方案，并在整个非线性时间演化过程中的不同阶段进行了线性稳定性分析，以包含这些物理特性并改进线性结果。这些新的非线性到线性模拟证实了之前的发现。这一结果表明，在热核实验堆中触发燃料芯块 ELM 可能需要比目前计划的大得多的燃料芯块，这使得 ELM 步调在操作上具有挑战性。另一方面，从高场侧注入的燃料颗粒很可能不会在 ELM 稳定的等离子体中无意触发 ELM。
{"title":"Prediction of pellet mass thresholds for ELM triggering in low-collisionality, ITER-like discharges","authors":"A. Wingen, R. S. Wilcox, B. C. Lyons, L. Baylor, N. Ferraro","doi":"10.1088/1741-4326/ad3f30","DOIUrl":"https://doi.org/10.1088/1741-4326/ad3f30","url":null,"abstract":"\u0000 In ITER, pellets are calculated to require more than 8 times the mass than currently planned to reliably trigger ELMs. Unmitigated heat flux impulses from edge-localized modes (ELMs) are intolerable in ITER at full power and current. Therefore, ITER operation relies on multiple approaches to control ELM heat fluxes. One method is pellet ELM pacing to instigate small rapid ELMs with low heat flux. Predicting the performance of pellet pacing is critical for ITER, which is expected to operate in a regime with a low-collisionality, peeling-limited pedestal. However, to trigger ELMs the local pressure increase in the expanding pellet cloud pushes the equilibrium over the ballooning stability limit. In this work, linear and nonlinear M3D-C1 simulations are used to predict pellet mass thresholds in DIII-D discharges and ITER scenarios with peeling-limited pedestals. It is found that the distance of the equilibrium's operational point from the ballooning branch of the pedestal stability boundary strongly changes thresholds. Linear M3D-C1 simulations find a strong dependence of the pellet mass threshold on the poloidal injection location for ITER's 15 MA, Q=10 scenario. The required pellet mass at the planned injection locations is 8 to 17 times larger than currently considered. However, such linear simulations do not include pellet ablation physics or time evolution of density and temperature. A new scheme of 2D nonlinear simulations, coupled with linear stability analysis at various steps throughout the nonlinear time evolution, was developed to include such physics and improve on the linear results. These new nonlinear-to-linear simulations confirm previous findings. This result suggests that pellet ELM triggering in ITER could require pellets much larger than those currently planned, which makes ELM-pacing operationally challenging. On the other hand, fueling pellets injected from the high-field side will likely not unintentionally trigger ELMs in an otherwise ELM-stable plasma.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"56 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140695582","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 : 2024-04-16DOI: 10.1088/1741-4326/ad3f2e
M. Kobayashi, Sachiko Yoshihashi, Kunihiro Ogawa, Mitsutaka Isobe, Tsukasa Aso, Masanori Hara, S. Sangaroon, S. Tamaki, I. Murata, S. Toyama, M. Miwa, S. Matsuyama, Masaki Osakabe
This paper presents the development of a simultaneous measurement method for fast neutron energy spectra and tritium production rates within mixed radiation fields using a single crystal Chemical Vapor Deposition (CVD) diamond detector (SDD) combined with a lithium fluoride (LiF) foil. The method involves the separation of pulses with rectangular shapes and the determination of the depth position within the single crystal diamond (SCD) struck by fast neutrons or nuclear reaction products including recoil tritons from the LiF foil based on pulse width, extracting pulse events occurred at the specific bulk region and the surface region of the SCD. Subsequently, unfolding techniques were employed to analyse the energy deposition spectrum of pulses at the specific bulk region which are induced only by fast neutrons, allowing the deduction of the fast neutron energy spectrum. To evaluate the tritium production rate, the energy deposition spectrum of pulses from events occurring at the SCD surface facing the LiF foil was analysed. By estimating the energy deposition spectrum solely induced by fast neutrons striking the SCD surface and subtracting it from the energy deposition spectrum of events at the SCD surface, the contribution of energetic ions, such as recoil tritons generated by the 6Li(n,α)3H reaction in the LiF foil, was determined. The fast neutron flux and tritium production rate obtained through this study were consistent with particle transport calculations, demonstrating the successful development of a method suitable for performance testing of fusion reactor blankets.
{"title":"Simultaneous measurements for fast neutron flux and tritium production rate using pulse shape discrimination and single crystal CVD diamond detector","authors":"M. Kobayashi, Sachiko Yoshihashi, Kunihiro Ogawa, Mitsutaka Isobe, Tsukasa Aso, Masanori Hara, S. Sangaroon, S. Tamaki, I. Murata, S. Toyama, M. Miwa, S. Matsuyama, Masaki Osakabe","doi":"10.1088/1741-4326/ad3f2e","DOIUrl":"https://doi.org/10.1088/1741-4326/ad3f2e","url":null,"abstract":"\u0000 This paper presents the development of a simultaneous measurement method for fast neutron energy spectra and tritium production rates within mixed radiation fields using a single crystal Chemical Vapor Deposition (CVD) diamond detector (SDD) combined with a lithium fluoride (LiF) foil. The method involves the separation of pulses with rectangular shapes and the determination of the depth position within the single crystal diamond (SCD) struck by fast neutrons or nuclear reaction products including recoil tritons from the LiF foil based on pulse width, extracting pulse events occurred at the specific bulk region and the surface region of the SCD. Subsequently, unfolding techniques were employed to analyse the energy deposition spectrum of pulses at the specific bulk region which are induced only by fast neutrons, allowing the deduction of the fast neutron energy spectrum. To evaluate the tritium production rate, the energy deposition spectrum of pulses from events occurring at the SCD surface facing the LiF foil was analysed. By estimating the energy deposition spectrum solely induced by fast neutrons striking the SCD surface and subtracting it from the energy deposition spectrum of events at the SCD surface, the contribution of energetic ions, such as recoil tritons generated by the 6Li(n,α)3H reaction in the LiF foil, was determined. The fast neutron flux and tritium production rate obtained through this study were consistent with particle transport calculations, demonstrating the successful development of a method suitable for performance testing of fusion reactor blankets.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"71 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140695438","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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