Pub Date : 2024-05-22DOI: 10.1088/1741-4326/ad4ef5
A.J. Coelho, J. Loizu, Paolo Ricci, Zeno Tecchiolli
The implementation of three-dimensional magnetic fields, such as the ones of stellarators, in the GBS code [textit{P. Ricci et al., PPCF textbf{54}(2012); M. Giacomin et al., JCP textbf{464} (2022)}] is presented, and simulation results are discussed. The geometrical operators appearing in the drif-reduced Braginskii equations evolved by GBS are expanded considering the typical parameter ordering of stellarator configurations. It turns out that most of the operators have a similar structure as the one implemented in the tokamak axisymmetric version of the code. In particular, the perpendicular laplacian only acts on the poloidal plane, which avoids the need of a three-dimensional solver for the electrostatic potential. The simulation of an island divertor stellarator is then presented, showing the derivation of the magnetic equilibrium in detail and extending the results in [textit{A.J. Coelho et al., Nucl. Fusion textbf{62} (2022)}]. Although the island magnetic field-lines divert the plasma towards the strike points of the walls, the islands do not seem to have a significant impact on the turbulence properties. The dominant mode, identified as interchange-driven, is field-aligned and breaks the stellarator toroidal symmetry. The radial and poloidal extensions of the mode are of the same order, in contrast to typical tokamak simulations. This has consequences on the poloidal dependence of turbulent transport.
在 GBS 代码[textit{P. Ricci et al.Ricci et al., PPCF textbf{54}(2012); M. Giacomin et al., JCP textbf{464} (2022)}] 中的三维磁场，并讨论了模拟结果。考虑到恒星器构型的典型参数排序，扩展了由 GBS 演化出的漂移还原布拉金斯基方程中出现的几何算子。结果发现，大多数算子与托卡马克轴对称版代码中的算子结构相似。尤其是垂直拉普拉斯只作用于极面，这就避免了静电势三维求解器的需要。然后介绍了岛式分流恒星器的模拟，详细展示了磁平衡的推导，并扩展了[textit{A.J. Coelho et al., Nucl. Fusion textbf{62} (2022)}]中的结果。虽然岛屿磁场线将等离子体引向壁的撞击点，但岛屿似乎对湍流特性没有显著影响。被确定为交换驱动的主导模式是场对齐模式，它打破了恒星器的环形对称性。与典型的托卡马克模拟不同，该模式的径向和极向延伸是同阶的。这对湍流传输的极坐标依赖性产生了影响。
{"title":"Global fluid simulation of plasma turbulence in stellarators with the GBS code","authors":"A.J. Coelho, J. Loizu, Paolo Ricci, Zeno Tecchiolli","doi":"10.1088/1741-4326/ad4ef5","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4ef5","url":null,"abstract":"\u0000 The implementation of three-dimensional magnetic fields, such as the ones of stellarators, in the GBS code [textit{P. Ricci et al., PPCF textbf{54}(2012); M. Giacomin et al., JCP textbf{464} (2022)}] is presented, and simulation results are discussed. The geometrical operators appearing in the drif-reduced Braginskii equations evolved by GBS are expanded considering the typical parameter ordering of stellarator configurations. It turns out that most of the operators have a similar structure as the one implemented in the tokamak axisymmetric version of the code. In particular, the perpendicular laplacian only acts on the poloidal plane, which avoids the need of a three-dimensional solver for the electrostatic potential. The simulation of an island divertor stellarator is then presented, showing the derivation of the magnetic equilibrium in detail and extending the results in [textit{A.J. Coelho et al., Nucl. Fusion textbf{62} (2022)}]. Although the island magnetic field-lines divert the plasma towards the strike points of the walls, the islands do not seem to have a significant impact on the turbulence properties. The dominant mode, identified as interchange-driven, is field-aligned and breaks the stellarator toroidal symmetry. The radial and poloidal extensions of the mode are of the same order, in contrast to typical tokamak simulations. This has consequences on the poloidal dependence of turbulent transport.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"27 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141109238","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 : 2024-05-21DOI: 10.1088/1741-4326/ad4e46
N. den Harder, M. Barnes, B. Heinemann, M. Lindqvist, R. Nocentini, G. Orozco, Christian Wimmer, Dirk Wünderlich, U. Fantz, Pierluigi Veltri
A low beamlet divergence is crucial for the efficiency of the ITER-NBI systems, since it affects the transmission of the beam through the duct. There is a requirement of 7 mrad e-folding divergence for the ITER Heating Neutral Beam. Significantly higher divergences (10-15 mrad) have been observed in RF-source based experiments albeit at low beam energy. This could be the consequence of a broad perpendicular velocity distribution of the H-/D- particles before extraction. This paper explores this hypothesis and its implications for ITER. To estimate H-/D- perpendicular temperatures in the RF-driven BATMAN Upgrade test facility, spatially resolved measurements of the beam power density are compared with IBSimu calculations. The estimated perpendicular temperatures show a strong dependence on the source filling pressure, decreasing from approximately 4 eV at 0.3 Pa to 2 eV at 0.4 Pa. Ion-optics calculations of the ITER-HNB grid system are performed to evaluate whether the temperatures estimated in the BATMAN Upgrade test facility are tolerable in view of beam-grid interaction and beamline transmission. The beamline transmission is fairly insensitive to the perpendicular temperature, but the heat loads at the downstream grids increase with the perpendicular temperature.
小光束发散度低对热核实验堆-NBI 系统的效率至关重要，因为它会影响光束通过管道的传输。要求热核实验堆加热中性光束的电子折叠发散度为 7 mrad。在基于射频源的实验中，尽管光束能量较低，却观察到了明显更高的发散（10-15 mrad）。这可能是萃取前 H-/D- 粒子广泛垂直速度分布的结果。本文探讨了这一假设及其对热核实验堆的影响。为了估算射频驱动的 BATMAN 升级试验设备中的 H-/D- 垂直温度，将空间分辨率测量的光束功率密度与 IBSimu 计算结果进行了比较。对热核实验堆-HNB 栅格系统进行了离子光学计算，以评估 BATMAN 升级版测试设施中估算的温度是否可以承受光束-栅格相互作用和光束线传输。光束线传输对垂直温度相当不敏感，但下游网格的热负荷会随着垂直温度的升高而增加。
{"title":"Beam optics of RF ion sources in view of ITER's NBI systems","authors":"N. den Harder, M. Barnes, B. Heinemann, M. Lindqvist, R. Nocentini, G. Orozco, Christian Wimmer, Dirk Wünderlich, U. Fantz, Pierluigi Veltri","doi":"10.1088/1741-4326/ad4e46","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4e46","url":null,"abstract":"\u0000 A low beamlet divergence is crucial for the efficiency of the ITER-NBI systems, since it affects the transmission of the beam through the duct. There is a requirement of 7 mrad e-folding divergence for the ITER Heating Neutral Beam. Significantly higher divergences (10-15 mrad) have been observed in RF-source based experiments albeit at low beam energy. This could be the consequence of a broad perpendicular velocity distribution of the H-/D- particles before extraction. This paper explores this hypothesis and its implications for ITER. To estimate H-/D- perpendicular temperatures in the RF-driven BATMAN Upgrade test facility, spatially resolved measurements of the beam power density are compared with IBSimu calculations. The estimated perpendicular temperatures show a strong dependence on the source filling pressure, decreasing from approximately 4 eV at 0.3 Pa to 2 eV at 0.4 Pa. Ion-optics calculations of the ITER-HNB grid system are performed to evaluate whether the temperatures estimated in the BATMAN Upgrade test facility are tolerable in view of beam-grid interaction and beamline transmission. The beamline transmission is fairly insensitive to the perpendicular temperature, but the heat loads at the downstream grids increase with the perpendicular temperature.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"30 26","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141118013","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 : 2024-05-20DOI: 10.1088/1741-4326/ad4db6
C. Marini, Eric M Hollmann, Shawn Wenjie Tang, J. Herfindal, Daisuke Shiraki, R. Wilcox, D. del-Castillo-Negrete, Minglei Yang, N. Eidietis, M. Hoppe
Current profile reconstructions are obtained for high current (Ip = 550 kA) post-disruption runaway electron (RE) plateau plasmas in DIII-D. Two novel methods of measuring the RE current profile in high-current RE plateaus are introduced and compared: localization of the q = 2 rational surface using visible synchrotron emission (SE) imaging and the measurement of the polarization angle of line-integrated Ar-II line emission. The two methods are found to be consistent with each other within the data uncertainties. Different simulations of the RE current profile are compared with the measurements: the toroidal fluid RE model is found to best fit the data, within the measurement uncertainties. In addition to introducing two novel methods to measure the RE current profile and validating present simulation capabilities, this work demonstrates that instabilities can grow at q = 2 and q = 1 surfaces without necessarily causing a RE final loss instability. Numerical simulations are also presented to elucidate the role of these instabilities on synchrotron emission.
对 DIII-D 中的高电流（Ip = 550 kA）中断后失控电子（RE）高原等离子体进行了电流剖面重建。介绍并比较了两种测量大电流RE高原中RE电流剖面的新方法：利用可见同步辐射（SE）成像定位q=2理性表面，以及测量线积分Ar-II线发射的偏振角。结果发现，在数据不确定性范围内，这两种方法是一致的。对 RE 电流曲线的不同模拟与测量结果进行了比较：发现环形流体 RE 模型在测量不确定性范围内最符合数据。除了引入两种测量 RE 电流曲线的新方法和验证目前的模拟能力之外，这项工作还证明了不稳定性可以在 q = 2 和 q = 1 表面增长，而不一定会导致 RE 最终损耗不稳定性。此外，还介绍了数值模拟，以阐明这些不稳定性对同步辐射的作用。
{"title":"Runaway electron plateau current profile reconstruction from synchrotron imaging and Ar-II line polarization angle measurements in DIII-D","authors":"C. Marini, Eric M Hollmann, Shawn Wenjie Tang, J. Herfindal, Daisuke Shiraki, R. Wilcox, D. del-Castillo-Negrete, Minglei Yang, N. Eidietis, M. Hoppe","doi":"10.1088/1741-4326/ad4db6","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4db6","url":null,"abstract":"\u0000 Current profile reconstructions are obtained for high current (Ip = 550 kA) post-disruption runaway electron (RE) plateau plasmas in DIII-D. Two novel methods of measuring the RE current profile in high-current RE plateaus are introduced and compared: localization of the q = 2 rational surface using visible synchrotron emission (SE) imaging and the measurement of the polarization angle of line-integrated Ar-II line emission. The two methods are found to be consistent with each other within the data uncertainties. Different simulations of the RE current profile are compared with the measurements: the toroidal fluid RE model is found to best fit the data, within the measurement uncertainties. In addition to introducing two novel methods to measure the RE current profile and validating present simulation capabilities, this work demonstrates that instabilities can grow at q = 2 and q = 1 surfaces without necessarily causing a RE final loss instability. Numerical simulations are also presented to elucidate the role of these instabilities on synchrotron emission.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"6 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141120216","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 : 2024-05-20DOI: 10.1088/1741-4326/ad4db5
A. Žohar, A. Trkov, Anders Hjalmarsson, Ž. Štancar, G. Zerovnik, Jan Malec, L. Snoj
To computationally support hydrogen and helium plasma discharges in the early stages of tokamak operation and to support the commissioning of the neutron detectors during these operational phases, creation of a realistic neutron and gamma ray particle source for Monte Carlo simulations will be needed. One of the most important parts of creating the particle source is calculating the reaction rates of the particle-emitting reactions to determine the emission profile in the plasma and the energy spectra of the emitted particles. In this paper the analysis and evaluation of cross sections for important neutron-emitting reactions, namely, 9Be(p,nγ)9B, 9Be(3He,nγ) 11C and charged-particle emission reactions 9Be(p,d)2α and 9Be(p,α)6Li that cause neutron emission in the next step of interactions are presented. The reaction cross sections were evaluated based on experimental measurements and empirical models describing the interaction of two charged particles. Evaluation of the associated uncertainties was also performed. The main goal of the work is to propose the newly evaluated cross sections for inclusion in the FENDL nuclear data library, thus making the cross section available to other researchers studying the above listed reactions.
{"title":"Evaluation of cross sections for fast ion reactions with beryllium in helium and hydrogen fusion plasmas","authors":"A. Žohar, A. Trkov, Anders Hjalmarsson, Ž. Štancar, G. Zerovnik, Jan Malec, L. Snoj","doi":"10.1088/1741-4326/ad4db5","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4db5","url":null,"abstract":"\u0000 To computationally support hydrogen and helium plasma discharges in the early stages of tokamak operation and to support the commissioning of the neutron detectors during these operational phases, creation of a realistic neutron and gamma ray particle source for Monte Carlo simulations will be needed. One of the most important parts of creating the particle source is calculating the reaction rates of the particle-emitting reactions to determine the emission profile in the plasma and the energy spectra of the emitted particles. In this paper the analysis and evaluation of cross sections for important neutron-emitting reactions, namely, 9Be(p,nγ)9B, 9Be(3He,nγ) 11C and charged-particle emission reactions 9Be(p,d)2α and 9Be(p,α)6Li that cause neutron emission in the next step of interactions are presented. The reaction cross sections were evaluated based on experimental measurements and empirical models describing the interaction of two charged particles. Evaluation of the associated uncertainties was also performed. The main goal of the work is to propose the newly evaluated cross sections for inclusion in the FENDL nuclear data library, thus making the cross section available to other researchers studying the above listed reactions.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"81 19","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141123121","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 : 2024-04-24DOI: 10.1088/1741-4326/ad4270
Xianzu Gong
Since the 2021 IAEA FEC, EAST experiments have been carried out in support of high-performance steady-state operation and physics understanding for ITER and CFETR. The first demonstration of reproducible 403 s long-pulse steady-state H-mode plasma with H98y2>1.3, βP~2.5, βN~1.6, ne/nGW~0.7 and a good control of impurity and heat exhaust have been achieved on EAST using the pure radio frequency (RF) power heating and current drive. In support of ITER and CFETR long pulse operation, a thousand-second time scale (~1056 s) fully non-inductive plasma has been achieved. The EAST operational regime of high βP has been significantly extended (H98y2>1.3, βP~4.0, βN~2.4 and ne/nGW~1.0) using RF and neutral beam (NB). The full edge localized mode suppression using the n = 4 resonant magnetic perturbations (RMP) has been achieved in ITER-like standard type-I ELMy H-mode plasmas with q95 ≈ 3.1 on EAST, extrapolating favorably to the ITER baseline scenario. The sustained large ELM control and stable partial detachment have been achieved with Ne seeding. The plasma-beta effect for error field penetration is investigated with n = 1 RMP. Breakdown and plasma initiation at low toroidal electric fields (<0.3 V/m) with EC pre-ionization is developed. The transport and control of high-Z impurity of tungsten is investigated.
自 2021 年国际原子能机构论坛以来，已经开展了 EAST 实验，以支持 ITER 和 CFETR 的高性能稳态运行和物理理解。利用纯射频（RF）功率加热和电流驱动，在 EAST 上首次演示了可重复的 403 s 长脉冲稳态 H 模式等离子体，其 H98y2>1.3, βP~2.5, βN~1.6, ne/nGW~0.7 以及对杂质和排热的良好控制。为支持ITER和CFETR长脉冲运行，实现了千秒时间尺度（约1056秒）的完全无感等离子体。利用射频和中性束（NB），高βP 的 EAST 运行机制得到了显著扩展（H98y2>1.3、βP~4.0、βN~2.4 和 ne/nGW~1.0）。在类似于热核聚变实验堆的标准 I 型 ELMy H 模式等离子体中，利用 n = 4 共振磁扰动（RMP）实现了全边缘局部模式抑制，EAST 上的 q95 ≈ 3.1，这与热核聚变实验堆的基线方案相差无几。使用 Ne 种子实现了持续的大 ELM 控制和稳定的部分脱离。使用 n = 1 RMP 研究了误差场穿透的等离子体-β效应。开发了在低环形电场（<0.3 V/m）下使用 EC 预电离的击穿和等离子体启动。研究了钨的高 Z 杂质的传输和控制。
{"title":"Overview of recent experimental results on the EAST tokamak","authors":"Xianzu Gong","doi":"10.1088/1741-4326/ad4270","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4270","url":null,"abstract":"\u0000 Since the 2021 IAEA FEC, EAST experiments have been carried out in support of high-performance steady-state operation and physics understanding for ITER and CFETR. The first demonstration of reproducible 403 s long-pulse steady-state H-mode plasma with H98y2>1.3, βP~2.5, βN~1.6, ne/nGW~0.7 and a good control of impurity and heat exhaust have been achieved on EAST using the pure radio frequency (RF) power heating and current drive. In support of ITER and CFETR long pulse operation, a thousand-second time scale (~1056 s) fully non-inductive plasma has been achieved. The EAST operational regime of high βP has been significantly extended (H98y2>1.3, βP~4.0, βN~2.4 and ne/nGW~1.0) using RF and neutral beam (NB). The full edge localized mode suppression using the n = 4 resonant magnetic perturbations (RMP) has been achieved in ITER-like standard type-I ELMy H-mode plasmas with q95 ≈ 3.1 on EAST, extrapolating favorably to the ITER baseline scenario. The sustained large ELM control and stable partial detachment have been achieved with Ne seeding. The plasma-beta effect for error field penetration is investigated with n = 1 RMP. Breakdown and plasma initiation at low toroidal electric fields (<0.3 V/m) with EC pre-ionization is developed. The transport and control of high-Z impurity of tungsten is investigated.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"41 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140664646","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 : 2024-04-24DOI: 10.1088/1741-4326/ad42b2
M. Valovic, Spyridon Aleiferis, Peter Blatchford, A. Boboc, Mathias Brix, Pedro Carvalho, I. S. Carvalho, Josep Maria Fontdecaba Climent, D. Dunai, L. Frassinetti, L. Garzotti, Florian Koechl, Christopher G Lowry, E. de la Luna, C. Maggi, R. Bianchetti Morales, Silvana Nowak, cameron Olde, D. Réfy, F. Rimini, S. Silburn, Ž. Štancar, G. Tvalashvili, M. Vécsei
A baseline scenario of deuterium-tritium (D-T) plasma with peripheral high field side fuelling pellets has been produced on JET in order to mimic the situation in ITER. The isotope mix ratio is controlled in order to target the value of 50%-50% by combination of tritium gas puffing and deuterium pellet injection. Multiple factors controlling the fuelling efficiency of individual pellets are analysed with following findings: (1) prompt particle losses due to pellet triggered ELMs are detected, (2) plasmoids drift velocity might be smaller than predicted by simulation, (3) post-pellet particle loss is controlled by transient ELMy phases. Overall pellet particle flux normalised to heat flux is similar to that in previous pellet fuelling experiments on AUG and JET.
为了模拟国际热核实验堆的情况，在 JET 上制作了带有外围高场侧燃料颗粒的氘-氚（D-T）等离子体基线方案。通过氚气体膨化和氘颗粒注入相结合的方式控制同位素混合比，使其达到 50%-50%的目标值。对控制单个颗粒燃料效率的多种因素进行了分析，并得出以下结论：（1）检测到颗粒触发 ELM 导致的颗粒损失，（2）质子漂移速度可能小于模拟预测值，（3）颗粒后颗粒损失受瞬态 ELMy 阶段控制。颗粒粒子通量与热通量的总体关系与之前在 AUG 和 JET 上进行的颗粒燃料实验相似。
{"title":"Fuelling of deuterium-tritium plasma by peripheral pellets in JET experiments","authors":"M. Valovic, Spyridon Aleiferis, Peter Blatchford, A. Boboc, Mathias Brix, Pedro Carvalho, I. S. Carvalho, Josep Maria Fontdecaba Climent, D. Dunai, L. Frassinetti, L. Garzotti, Florian Koechl, Christopher G Lowry, E. de la Luna, C. Maggi, R. Bianchetti Morales, Silvana Nowak, cameron Olde, D. Réfy, F. Rimini, S. Silburn, Ž. Štancar, G. Tvalashvili, M. Vécsei","doi":"10.1088/1741-4326/ad42b2","DOIUrl":"https://doi.org/10.1088/1741-4326/ad42b2","url":null,"abstract":"\u0000 A baseline scenario of deuterium-tritium (D-T) plasma with peripheral high field side fuelling pellets has been produced on JET in order to mimic the situation in ITER. The isotope mix ratio is controlled in order to target the value of 50%-50% by combination of tritium gas puffing and deuterium pellet injection. Multiple factors controlling the fuelling efficiency of individual pellets are analysed with following findings: (1) prompt particle losses due to pellet triggered ELMs are detected, (2) plasmoids drift velocity might be smaller than predicted by simulation, (3) post-pellet particle loss is controlled by transient ELMy phases. Overall pellet particle flux normalised to heat flux is similar to that in previous pellet fuelling experiments on AUG and JET.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"3 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140665123","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 : 2024-04-23DOI: 10.1088/1741-4326/ad41c4
Sizhe Duan, Xiang Zhu, Huishan Cai
The effect of different off-axis energetic particle (EP) slowing down distribution on beta-induced Alfven eigenmode (BAE), driven by the on-axis EP distribution, is systematically studied using kinetic-magnetohydrodynamic code M3D-K. The aim is to analyze the optimal parameter region for controlling AEs via varying EP distribution parameters. The simulation results reveal that by modifying the gradients of the EP distribution, the off-axis EP can further destabilize or mitigate the on-axis EP driven BAE, depending on the off-axis EP distribution's parameters: deposition profile, EP beta, pitch angle, injection velocity and direction. When the off-axis EP is deposited outside the mode center, and its injection velocity is sufficiently large to satisfy the resonance with BAE, the stabilization of BAE is achieved. This stabilizing effect is directly proportional to the off-axis EP beta, while excessive off-axis EP beta can trigger a new EP-driven instability located outside the BAE. Furthermore, to achieve a stronger stabilizing effect, the pitch angle distribution and velocity direction of the off-axis EP should be close to those of the on-axis EP. For instance, compared to the counter-passing off-axis EP, the co-passing off-axis EP can lead to a more effective mitigation of the BAE driven by the co-passing on-axis EP.
利用动力学-磁流体动力学代码 M3D-K，系统地研究了不同的离轴高能粒子（EP）减速分布对由轴向 EP 分布驱动的贝塔诱导阿尔芬特征模（BAE）的影响。目的是分析通过改变 EP 分布参数来控制 AE 的最佳参数区域。模拟结果表明，通过改变 EP 分布的梯度，轴外 EP 可以进一步破坏或减轻轴内 EP 驱动的 BAE，具体取决于轴外 EP 分布的参数：沉积剖面、EP β、俯仰角、注入速度和方向。当离轴 EP 沉积在模式中心之外，并且其注入速度足够大以满足与 BAE 的共振时，就会实现 BAE 的稳定。这种稳定效果与离轴 EP beta 值成正比，而过大的离轴 EP beta 值会引发位于 BAE 外部的新的 EP 驱动不稳定。此外，为了达到更强的稳定效果，离轴 EP 的俯仰角分布和速度方向应与轴上 EP 的俯仰角分布和速度方向接近。例如，与反通过的离轴 EP 相比，共通过的离轴 EP 可以更有效地缓解由共通过的轴上 EP 驱动的 BAE。
{"title":"Simulations of beta-induced Alfvén eigenmode mitigation by off-axis energetic particle distribution","authors":"Sizhe Duan, Xiang Zhu, Huishan Cai","doi":"10.1088/1741-4326/ad41c4","DOIUrl":"https://doi.org/10.1088/1741-4326/ad41c4","url":null,"abstract":"\u0000 The effect of different off-axis energetic particle (EP) slowing down distribution on beta-induced Alfven eigenmode (BAE), driven by the on-axis EP distribution, is systematically studied using kinetic-magnetohydrodynamic code M3D-K. The aim is to analyze the optimal parameter region for controlling AEs via varying EP distribution parameters. The simulation results reveal that by modifying the gradients of the EP distribution, the off-axis EP can further destabilize or mitigate the on-axis EP driven BAE, depending on the off-axis EP distribution's parameters: deposition profile, EP beta, pitch angle, injection velocity and direction. When the off-axis EP is deposited outside the mode center, and its injection velocity is sufficiently large to satisfy the resonance with BAE, the stabilization of BAE is achieved. This stabilizing effect is directly proportional to the off-axis EP beta, while excessive off-axis EP beta can trigger a new EP-driven instability located outside the BAE. Furthermore, to achieve a stronger stabilizing effect, the pitch angle distribution and velocity direction of the off-axis EP should be close to those of the on-axis EP. For instance, compared to the counter-passing off-axis EP, the co-passing off-axis EP can lead to a more effective mitigation of the BAE driven by the co-passing on-axis EP.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"24 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140667528","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 : 2024-04-22DOI: 10.1088/1741-4326/ad4168
A. Di Siena, Roberto Bilato, A. Bañón Navarro, Michael George Bergmann, L. Leppin, T. Görler, E. Poli, Markus Weiland, G. Tardini, F. Jenko
This paper presents global gyrokinetic simulations on the transport time scale of an ASDEX Upgrade H-mode discharge showing a pronounced peaking of the on-axis ion temperature profiles. Leveraging the newly developed GENE-Tango tool, which combines the global gyrokinetic code GENE with the transport solver Tango, we investigate the impact of energetic particles and electromagnetic effects on the improved plasma performance observed in the experimental discharge. Our results reveal that a striking agreement between the GENE-Tango simulations and the experimental measurements can be achieved only when energetic particles and electromagnetic effects are simultaneously retained in the modeling. In contrast, when these are neglected we observed a significant underestimation of the on-axis ion temperature, aligning with profiles computed using TGLF-ASTRA. The peaking in the ion temperature profile observed in the simulations can be attributed to the effective suppression of turbulence by high-frequency electromagnetic modes, likely Kinetic Ballooning Modes (KBM) / Alfv'en eigenmodes (AEs). These modes play a critical role in enhancing zonal flow activity and shearing rate levels which thus lead to a localized increase in the temperature gradient. However, it is crucial to maintain these modes at a state of marginal stability or weak instability to prevent energetic particle turbulence destabilization. Otherwise, the result would be a flattening of all the thermal profiles. Interestingly, we found that global GENE-Tango simulations are required to model correctly the linear dynamics of these high-frequency modes. Additionally, global simulations demonstrate greater tolerance than flux-tube simulations for marginal instability of these high frequency modes while maintaining power balance agreement.
{"title":"Impact of supra-thermal particles on plasma performance at ASDEX Upgrade with GENE-Tango simulations","authors":"A. Di Siena, Roberto Bilato, A. Bañón Navarro, Michael George Bergmann, L. Leppin, T. Görler, E. Poli, Markus Weiland, G. Tardini, F. Jenko","doi":"10.1088/1741-4326/ad4168","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4168","url":null,"abstract":"\u0000 This paper presents global gyrokinetic simulations on the transport time scale of an ASDEX Upgrade H-mode discharge showing a pronounced peaking of the on-axis ion temperature profiles. Leveraging the newly developed GENE-Tango tool, which combines the global gyrokinetic code GENE with the transport solver Tango, we investigate the impact of energetic particles and electromagnetic effects on the improved plasma performance observed in the experimental discharge. Our results reveal that a striking agreement between the GENE-Tango simulations and the experimental measurements can be achieved only when energetic particles and electromagnetic effects are simultaneously retained in the modeling. In contrast, when these are neglected we observed a significant underestimation of the on-axis ion temperature, aligning with profiles computed using TGLF-ASTRA. The peaking in the ion temperature profile observed in the simulations can be attributed to the effective suppression of turbulence by high-frequency electromagnetic modes, likely Kinetic Ballooning Modes (KBM) / Alfv'en eigenmodes (AEs). These modes play a critical role in enhancing zonal flow activity and shearing rate levels which thus lead to a localized increase in the temperature gradient. However, it is crucial to maintain these modes at a state of marginal stability or weak instability to prevent energetic particle turbulence destabilization. Otherwise, the result would be a flattening of all the thermal profiles. Interestingly, we found that global GENE-Tango simulations are required to model correctly the linear dynamics of these high-frequency modes. Additionally, global simulations demonstrate greater tolerance than flux-tube simulations for marginal instability of these high frequency modes while maintaining power balance agreement.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"05 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140676555","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 : 2024-04-22DOI: 10.1088/1741-4326/ad4169
D. Moseev, M. Zanini, H. Kasahara, Heinrich Laqua, H. Funaba, Wataru Hayashi, W. Heidbrink, K. Ida, H. Igami, Yasuko Kawamoto, Naoki Kenmochi, S. Lazerson, Masaki Nishiura, R. Ochoukov, Kunihiro Ogawa, M. R. Larsen, M. Salewski, T. Seki, N. Tamura, Kenji Tanaka, T. Tokuzawa, M. Yoshinuma
Sawtooth oscillations in tokamaks frequently lead to the redistribution of energetic ions, mainly on passing orbits, causing their expulsion from the core. This paper discusses the first measurements of the interaction of fast ions and sawteeth in the Large Helical Device (LHD). The crashes, caused by changed rotational transform profile due to electron cyclotron current drive (ECCD) and neutral beam current drive (NBCD), show no redistribution effect on fast ions in the core or at the edge.
{"title":"Influence of sawtooth oscillations on fast ions in a stellarator","authors":"D. Moseev, M. Zanini, H. Kasahara, Heinrich Laqua, H. Funaba, Wataru Hayashi, W. Heidbrink, K. Ida, H. Igami, Yasuko Kawamoto, Naoki Kenmochi, S. Lazerson, Masaki Nishiura, R. Ochoukov, Kunihiro Ogawa, M. R. Larsen, M. Salewski, T. Seki, N. Tamura, Kenji Tanaka, T. Tokuzawa, M. Yoshinuma","doi":"10.1088/1741-4326/ad4169","DOIUrl":"https://doi.org/10.1088/1741-4326/ad4169","url":null,"abstract":"\u0000 Sawtooth oscillations in tokamaks frequently lead to the redistribution of energetic ions, mainly on passing orbits, causing their expulsion from the core. This paper discusses the first measurements of the interaction of fast ions and sawteeth in the Large Helical Device (LHD). The crashes, caused by changed rotational transform profile due to electron cyclotron current drive (ECCD) and neutral beam current drive (NBCD), show no redistribution effect on fast ions in the core or at the edge.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"50 22","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140672935","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 : 2024-04-19DOI: 10.1088/1741-4326/ad40c0
T. Long, P. H. Diamond, R. Ke, Zhipeng Chen, M. Cao, Xin Xu, Min Xu, Rongjie Hong, Wenjing Tian, Jinbang Yuan, Yanmin Liu, Qinghao Yan, Qinghu Yang, C. Shen, Weixin Guo, Lu Wang, Lin Nie, Zhanhui Wang, G. Hao, Nengchao Wang, Z. Chen, Y. Pan, Jiquan Li, Wei Chen, Wulyu Zhong
We report on comprehensive experimental studies of turbulence spreading in edge plasmas. These studies demonstrate the relation of turbulence spreading and entrainment to intermittent convective density fluctuation events or bursts (i.e. blobs and holes). The non-diffusive character of turbulence spreading is thus elucidated. The turbulence spreading velocity (or mean jet velocity) manifests a linear correlation with the skewness of density fluctuations, and increases with the auto-correlation time of density fluctuations. Turbulence spreading by positive density fluctuations is outward, while spreading by negative density fluctuations is inward. The degree of symmetry breaking between outward propagating blobs and inward propagating holes increases with the amplitude of density fluctuations. Thus, blob-hole asymmetry emerges as crucial to turbulence spreading. These results highlight the important role of intermittent convective events in conveying the spreading of turbulence, and constitute a fundamental challenge to existing diffusive models of spreading.
{"title":"On how structures convey non-diffusive turbulence spreading","authors":"T. Long, P. H. Diamond, R. Ke, Zhipeng Chen, M. Cao, Xin Xu, Min Xu, Rongjie Hong, Wenjing Tian, Jinbang Yuan, Yanmin Liu, Qinghao Yan, Qinghu Yang, C. Shen, Weixin Guo, Lu Wang, Lin Nie, Zhanhui Wang, G. Hao, Nengchao Wang, Z. Chen, Y. Pan, Jiquan Li, Wei Chen, Wulyu Zhong","doi":"10.1088/1741-4326/ad40c0","DOIUrl":"https://doi.org/10.1088/1741-4326/ad40c0","url":null,"abstract":"\u0000 We report on comprehensive experimental studies of turbulence spreading in edge plasmas. These studies demonstrate the relation of turbulence spreading and entrainment to intermittent convective density fluctuation events or bursts (i.e. blobs and holes). The non-diffusive character of turbulence spreading is thus elucidated. The turbulence spreading velocity (or mean jet velocity) manifests a linear correlation with the skewness of density fluctuations, and increases with the auto-correlation time of density fluctuations. Turbulence spreading by positive density fluctuations is outward, while spreading by negative density fluctuations is inward. The degree of symmetry breaking between outward propagating blobs and inward propagating holes increases with the amplitude of density fluctuations. Thus, blob-hole asymmetry emerges as crucial to turbulence spreading. These results highlight the important role of intermittent convective events in conveying the spreading of turbulence, and constitute a fundamental challenge to existing diffusive models of spreading.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":" 627","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140682518","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：