Pub Date : 2024-07-03DOI: 10.1088/1741-4326/ad5851
Kevin Verhaegh, James Harrison, Bruce Lipschultz, Nicola Lonigro, Stijn Kobussen, David Moulton, Nick Osborne, Peter Ryan, Christian Theiler, Tijs Wijkamp, Dominik Brida, Gijs Derks, Rhys Doyle, Fabio Federici, Antti Hakola, Stuart Henderson, Bob Kool, Sarah Newton, Ryoko Osawa, Xander Pope, Holger Reimerdes, Nicola Vianello, Marco Wischmeier, the EUROfusion Tokamak Exploitation Team and the MAST-U Team
This experimental study presents an in-depth investigation of the performance of the MAST-U Super-X divertor during NBI-heated operation (up to 2.5 MW) focussing on volumetric ion sources and sinks as well as power losses during detachment. The particle balance and power loss analysis revealed the crucial role of Molecular Activated Recombination and Dissociation (MAR and MAD) ion sinks in divertor particle and power balance, which remain pronounced in the change from ohmic to higher power (NBI heated) L-mode conditions. The importance of MAR and MAD remains with double the absorbed NBI heating. MAD results in significant power dissipation (up to of ), mostly in the cold ( eV) detached region. Theoretical and experimental evidence is found for the potential contribution of to MAR and MAD, which warrants further study. These results suggest that MAR and MAD can be relevant in higher power conditions than the ohmic conditions studied previously. Post-processing reactor-scale simulations suggests that MAR and MAD can play a significant role in divertor physics and synthetic diagnostic signals of reactor-scale devices, which are currently underestimated in exhaust simulations. This raises implications for the accuracy of reactor-scale divertor simulations of particularly tightly baffled (alternative) divertor configurations.
{"title":"Investigations of atomic and molecular processes of NBI-heated discharges in the MAST Upgrade Super-X divertor with implications for reactors","authors":"Kevin Verhaegh, James Harrison, Bruce Lipschultz, Nicola Lonigro, Stijn Kobussen, David Moulton, Nick Osborne, Peter Ryan, Christian Theiler, Tijs Wijkamp, Dominik Brida, Gijs Derks, Rhys Doyle, Fabio Federici, Antti Hakola, Stuart Henderson, Bob Kool, Sarah Newton, Ryoko Osawa, Xander Pope, Holger Reimerdes, Nicola Vianello, Marco Wischmeier, the EUROfusion Tokamak Exploitation Team and the MAST-U Team","doi":"10.1088/1741-4326/ad5851","DOIUrl":"https://doi.org/10.1088/1741-4326/ad5851","url":null,"abstract":"This experimental study presents an in-depth investigation of the performance of the MAST-U Super-X divertor during NBI-heated operation (up to 2.5 MW) focussing on volumetric ion sources and sinks as well as power losses during detachment. The particle balance and power loss analysis revealed the crucial role of Molecular Activated Recombination and Dissociation (MAR and MAD) ion sinks in divertor particle and power balance, which remain pronounced in the change from ohmic to higher power (NBI heated) L-mode conditions. The importance of MAR and MAD remains with double the absorbed NBI heating. MAD results in significant power dissipation (up to of ), mostly in the cold ( eV) detached region. Theoretical and experimental evidence is found for the potential contribution of to MAR and MAD, which warrants further study. These results suggest that MAR and MAD can be relevant in higher power conditions than the ohmic conditions studied previously. Post-processing reactor-scale simulations suggests that MAR and MAD can play a significant role in divertor physics and synthetic diagnostic signals of reactor-scale devices, which are currently underestimated in exhaust simulations. This raises implications for the accuracy of reactor-scale divertor simulations of particularly tightly baffled (alternative) divertor configurations.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"3 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141547528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.1088/1741-4326/ad58f3
D. Kennedy, C.M. Roach, M. Giacomin, P.G. Ivanov, T. Adkins, F. Sheffield, T. Görler, A. Bokshi, D. Dickinson, H.G. Dudding and B.S. Patel
This paper discusses the importance of parallel perturbations of the magnetic-field in gyrokinetic simulations of electromagnetic instabilities and turbulence at mid-radius in the burning plasma phase of the conceptual high-β, reactor-scale, tight-aspect-ratio tokamak STEP. Previous studies have revealed the presence of unstable hybrid kinetic ballooning modes (hKBMs) and subdominant microtearing modes at binormal scales approaching the ion Larmor radius. In this STEP plasma it was found that the hKBM requires the inclusion of parallel magnetic-field perturbations to be linearly unstable. Here, the extent to which the inclusion of fluctuations in the parallel magnetic-field can be relaxed is explored through gyrokinetic simulations. In particular, the frequently used MHD approximation (dropping and setting the drift frequency equal to the curvature drift frequency) is discussed and simulations explore whether this approximation is useful for modelling STEP plasmas. It is shown that the MHD approximation can reproduce some of the linear properties of the full STEP gyrokinetic system, but is too stable at low ky and nonlinear simulations using the MHD approximation result in very different transport states. It is demonstrated that the MHD approximation is challenged by the high values in STEP, and that the approximation improves considerably at lower . Furthermore, it is shown that the sensitivity of STEP to fluctuations is primarily because the plasma sits close to marginality and it is shown that in slightly more strongly driven conditions the hKBM is unstable without Crucially, it is demonstrated that the state of large transport typically predicted by local electromagnetic gyrokinetic simulations of STEP plasmas is not solely due to physics.
{"title":"On the importance of parallel magnetic-field fluctuations for electromagnetic instabilities in STEP","authors":"D. Kennedy, C.M. Roach, M. Giacomin, P.G. Ivanov, T. Adkins, F. Sheffield, T. Görler, A. Bokshi, D. Dickinson, H.G. Dudding and B.S. Patel","doi":"10.1088/1741-4326/ad58f3","DOIUrl":"https://doi.org/10.1088/1741-4326/ad58f3","url":null,"abstract":"This paper discusses the importance of parallel perturbations of the magnetic-field in gyrokinetic simulations of electromagnetic instabilities and turbulence at mid-radius in the burning plasma phase of the conceptual high-β, reactor-scale, tight-aspect-ratio tokamak STEP. Previous studies have revealed the presence of unstable hybrid kinetic ballooning modes (hKBMs) and subdominant microtearing modes at binormal scales approaching the ion Larmor radius. In this STEP plasma it was found that the hKBM requires the inclusion of parallel magnetic-field perturbations to be linearly unstable. Here, the extent to which the inclusion of fluctuations in the parallel magnetic-field can be relaxed is explored through gyrokinetic simulations. In particular, the frequently used MHD approximation (dropping and setting the drift frequency equal to the curvature drift frequency) is discussed and simulations explore whether this approximation is useful for modelling STEP plasmas. It is shown that the MHD approximation can reproduce some of the linear properties of the full STEP gyrokinetic system, but is too stable at low ky and nonlinear simulations using the MHD approximation result in very different transport states. It is demonstrated that the MHD approximation is challenged by the high values in STEP, and that the approximation improves considerably at lower . Furthermore, it is shown that the sensitivity of STEP to fluctuations is primarily because the plasma sits close to marginality and it is shown that in slightly more strongly driven conditions the hKBM is unstable without Crucially, it is demonstrated that the state of large transport typically predicted by local electromagnetic gyrokinetic simulations of STEP plasmas is not solely due to physics.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"1 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141530672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.1088/1741-4326/ad58f4
R. Maurizio, D. Thomas, J.H. Yu, T. Abrams, A.W. Hyatt, J. Herfindal, A. Leonard, X. Ma, A.G. McLean, J. Ren, F. Scotti, M.W. Shafer, G. Sinclair, H.Q. Wang and J. Watkins
Experiments in DIII-D demonstrate that the upstream plasma density to detach an un-pumped slot divertor is similar for a V-shaped and a flat-end slot, despite significantly higher neutral pressure in the V-shaped slot and in contrast to SOLPS-ITER predictions. The detachment threshold can be reduced by using in-slot instead of main-chamber gas fuelling or by placing the strike point on the inner slanted slot baffle instead of the slot end, as described by simulations with full drift physics. When increasing the plasma line-averaged density (without extrinsic impurities), the transition to detachment in DIII-D slot divertor is sharp and requires a high value of plasma density with the ion drift into the slot, whereas it is smooth and requires a lower value of plasma density with the opposite drift direction, in accord with detachment experiments in the DIII-D open lower divertor. Unique experiments on DIII-D and comparison to advanced simulations expand the scientific understanding of slot-shaped divertors, considered highly desirable for next step fusion devices.
{"title":"Experiments on plasma detachment in a V-shaped slot divertor in the DIII-D tokamak","authors":"R. Maurizio, D. Thomas, J.H. Yu, T. Abrams, A.W. Hyatt, J. Herfindal, A. Leonard, X. Ma, A.G. McLean, J. Ren, F. Scotti, M.W. Shafer, G. Sinclair, H.Q. Wang and J. Watkins","doi":"10.1088/1741-4326/ad58f4","DOIUrl":"https://doi.org/10.1088/1741-4326/ad58f4","url":null,"abstract":"Experiments in DIII-D demonstrate that the upstream plasma density to detach an un-pumped slot divertor is similar for a V-shaped and a flat-end slot, despite significantly higher neutral pressure in the V-shaped slot and in contrast to SOLPS-ITER predictions. The detachment threshold can be reduced by using in-slot instead of main-chamber gas fuelling or by placing the strike point on the inner slanted slot baffle instead of the slot end, as described by simulations with full drift physics. When increasing the plasma line-averaged density (without extrinsic impurities), the transition to detachment in DIII-D slot divertor is sharp and requires a high value of plasma density with the ion drift into the slot, whereas it is smooth and requires a lower value of plasma density with the opposite drift direction, in accord with detachment experiments in the DIII-D open lower divertor. Unique experiments on DIII-D and comparison to advanced simulations expand the scientific understanding of slot-shaped divertors, considered highly desirable for next step fusion devices.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"189 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141514854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-01DOI: 10.1088/1741-4326/ad5a1d
S. Wiesen, S. Dasbach, A. Kit, A.E. Jaervinen, A. Gillgren, A. Ho, A. Panera, D. Reiser, M. Brenzke, Y. Poels, E. Westerhof, V. Menkovski, G.F. Derks and P. Strand
A review is given on the highlights of a scatter-shot approach of developing machine-learning methods and artificial neural networks based fast predictors for the application to fusion exhaust. The aim is to enable and facilitate optimized and improved modeling allowing more flexible integration of physics models in the light of extrapolations towards future fusion devices. The project encompasses various research objectives: (a) developments of surrogate model predictors for power & particle exhaust in fusion power plants; (b) assessments of surrogate models for time-dependent phenomena in the plasma-edge; (c) feasibility studies of micro–macro model discovery for plasma-facing components surface morphology & durability; and (d) enhancements of pedestal models & databases through interpolators and generators exploiting uncertainty quantification. Presented results demonstrate useful applications for machine-learning and artificial intelligence in fusion exhaust modeling schemes, enabling an unprecedented combination of both fast and accurate simulation.
{"title":"Data-driven models in fusion exhaust: AI methods and perspectives","authors":"S. Wiesen, S. Dasbach, A. Kit, A.E. Jaervinen, A. Gillgren, A. Ho, A. Panera, D. Reiser, M. Brenzke, Y. Poels, E. Westerhof, V. Menkovski, G.F. Derks and P. Strand","doi":"10.1088/1741-4326/ad5a1d","DOIUrl":"https://doi.org/10.1088/1741-4326/ad5a1d","url":null,"abstract":"A review is given on the highlights of a scatter-shot approach of developing machine-learning methods and artificial neural networks based fast predictors for the application to fusion exhaust. The aim is to enable and facilitate optimized and improved modeling allowing more flexible integration of physics models in the light of extrapolations towards future fusion devices. The project encompasses various research objectives: (a) developments of surrogate model predictors for power & particle exhaust in fusion power plants; (b) assessments of surrogate models for time-dependent phenomena in the plasma-edge; (c) feasibility studies of micro–macro model discovery for plasma-facing components surface morphology & durability; and (d) enhancements of pedestal models & databases through interpolators and generators exploiting uncertainty quantification. Presented results demonstrate useful applications for machine-learning and artificial intelligence in fusion exhaust modeling schemes, enabling an unprecedented combination of both fast and accurate simulation.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"49 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141514856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-01DOI: 10.1088/1741-4326/ad5a1b
G.M. Staebler, J.M. Park, E. Hassan, C. Angioni, E. Fable, C. Bourdelle, J.E. Kinsey, C. Holland, E.A. Belli, T. Neiser, J. Candy and R.E. Waltz
A long standing shortfall in the predicted L-mode edge energy transport by reduced quasi-linear models of gyrokinetic turbulent transport has been resolved. The improved model TGLF-SAT2 has higher fidelity to gyrokinetic simulations of the electron-scale contribution to the electron energy transport and the ion-scale flux surface shape dependence of energy transport. The success of TGLF-SAT2 in predicting the L-mode and Ohmic edge profiles is critical to whole pulse simulation and opens the door to prediction of the H-mode power threshold.
陀螺动力湍流输运的简化准线性模型在预测 L 模式边缘能量输运方面长期存在的不足已经得到解决。改进后的 TGLF-SAT2 模型对电子尺度对电子能量传输的贡献和离子尺度能量传输的通量面形状依赖性的陀螺动力模拟具有更高的保真度。TGLF-SAT2 在预测 L 模式和欧姆边缘剖面方面的成功对于整个脉冲模拟至关重要，并为预测 H 模式功率阈值打开了大门。
{"title":"Successful prediction of tokamak transport in the L-mode regime","authors":"G.M. Staebler, J.M. Park, E. Hassan, C. Angioni, E. Fable, C. Bourdelle, J.E. Kinsey, C. Holland, E.A. Belli, T. Neiser, J. Candy and R.E. Waltz","doi":"10.1088/1741-4326/ad5a1b","DOIUrl":"https://doi.org/10.1088/1741-4326/ad5a1b","url":null,"abstract":"A long standing shortfall in the predicted L-mode edge energy transport by reduced quasi-linear models of gyrokinetic turbulent transport has been resolved. The improved model TGLF-SAT2 has higher fidelity to gyrokinetic simulations of the electron-scale contribution to the electron energy transport and the ion-scale flux surface shape dependence of energy transport. The success of TGLF-SAT2 in predicting the L-mode and Ohmic edge profiles is critical to whole pulse simulation and opens the door to prediction of the H-mode power threshold.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"30 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141514855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-30DOI: 10.1088/1741-4326/ad5a22
T. Ahmadi, Y. Ono, Y. Cai and H. Tanabe
This paper introduces an innovative method for reconstructing 2D magnetic flux contours and plasma parameters of dynamically moving tokamak plasmas. While conventional methods like EFIT, based on the Grad–Shafranov equation, are suitable for plasma equilibria with a single magnetic axis, our approach utilizes the MHD equations and shows promise for tokamak plasmas in motion or containing multiple magnetic axes, which may not strictly adhere to plasma equilibria. By utilizing limited edge magnetic probe measurements, our developed model successfully reconstructs the time evolution of two merging plasma toroids in the TS-6 experiment. A comparison with direct 2D magnetic probe measurements in a low β regime reveals a reconstruction error of approximately 3%.
{"title":"MHD-FiT: MHD-based dynamic reconstruction of tokamak plasma configuration","authors":"T. Ahmadi, Y. Ono, Y. Cai and H. Tanabe","doi":"10.1088/1741-4326/ad5a22","DOIUrl":"https://doi.org/10.1088/1741-4326/ad5a22","url":null,"abstract":"This paper introduces an innovative method for reconstructing 2D magnetic flux contours and plasma parameters of dynamically moving tokamak plasmas. While conventional methods like EFIT, based on the Grad–Shafranov equation, are suitable for plasma equilibria with a single magnetic axis, our approach utilizes the MHD equations and shows promise for tokamak plasmas in motion or containing multiple magnetic axes, which may not strictly adhere to plasma equilibria. By utilizing limited edge magnetic probe measurements, our developed model successfully reconstructs the time evolution of two merging plasma toroids in the TS-6 experiment. A comparison with direct 2D magnetic probe measurements in a low β regime reveals a reconstruction error of approximately 3%.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"11 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141514858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-30DOI: 10.1088/1741-4326/ad5a1f
M.-H. Aumeunier, A. Juven, J. Gerardin, C-M. B. Cisse, S. Pamela, R. Miorelli, C. Reboud, F. Retailleau, J. Marot, F. Rigollet and L. Marot
The protection of ITER in-vessel components and the plasma-wall interaction studies will be based on a large network of infrared (IR) cameras covering 70% of the tokamak. The surface temperature measurement from IR images remains challenging due to the presence of metallic targets, with changes in surface thermo-radiative properties (emissivity) and the presence of multiple reflections. The paper provides an overview of major progress to improve the interpretation of IR image and to get more reliable surface temperature from IR synthetic diagnostics. The paper presents the latest development of (1) the forward model to include the modelling of the edge localised modes and a new advanced camera that is better adapted to experimental data (2) the inverse model to retrieve the emissivity of the targets and the surface temperature from a neural network trained exclusively from synthetic IR images. Promising results have been obtained both from simulated test images with an estimated emissivity better than 0.05 and a surface temperature better than 10%, and from WEST experimental images of ITER-like wide-angle to filter reflection patterns.
热核实验堆容器内组件的保护和等离子体与壁的相互作用研究将基于覆盖 70% 托卡马克的大型红外（IR）摄像机网络。由于金属目标的存在、表面热辐射特性（发射率）的变化以及多重反射的存在，通过红外图像测量表面温度仍然具有挑战性。本文概述了在改进红外图像判读和从红外合成诊断中获得更可靠的表面温度方面取得的主要进展。论文介绍了以下方面的最新进展：(1)前向模型，包括边缘局部模式建模，以及更适合实验数据的新型先进照相机；(2)反向模型，通过完全由合成红外图像训练的神经网络检索目标的发射率和表面温度。从模拟测试图像（估计发射率优于 0.05，表面温度优于 10%）和类似于热核实验堆广角滤波反射模式的 WEST 实验图像中都获得了可喜的结果。
{"title":"Surface temperature measurement from infrared synthetic diagnostic in preparation for ITER operations","authors":"M.-H. Aumeunier, A. Juven, J. Gerardin, C-M. B. Cisse, S. Pamela, R. Miorelli, C. Reboud, F. Retailleau, J. Marot, F. Rigollet and L. Marot","doi":"10.1088/1741-4326/ad5a1f","DOIUrl":"https://doi.org/10.1088/1741-4326/ad5a1f","url":null,"abstract":"The protection of ITER in-vessel components and the plasma-wall interaction studies will be based on a large network of infrared (IR) cameras covering 70% of the tokamak. The surface temperature measurement from IR images remains challenging due to the presence of metallic targets, with changes in surface thermo-radiative properties (emissivity) and the presence of multiple reflections. The paper provides an overview of major progress to improve the interpretation of IR image and to get more reliable surface temperature from IR synthetic diagnostics. The paper presents the latest development of (1) the forward model to include the modelling of the edge localised modes and a new advanced camera that is better adapted to experimental data (2) the inverse model to retrieve the emissivity of the targets and the surface temperature from a neural network trained exclusively from synthetic IR images. Promising results have been obtained both from simulated test images with an estimated emissivity better than 0.05 and a surface temperature better than 10%, and from WEST experimental images of ITER-like wide-angle to filter reflection patterns.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"64 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141514857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-30DOI: 10.1088/1741-4326/ad5a1c
A. Marinoni, M.E. Austin, J. Candy, C. Chrystal, S.R. Haskey, M. Porkolab, J.C. Rost and F. Scotti
Nonlinear gyrokinetic simulations correctly predict particle as well as ion and electron energy fluxes of high confinement plasmas with a negative triangularity cross sectional shape, showing that core transport in these plasmas is well described by standard gyrokinetic models. Experimentally inferred power balance fluxes are mostly reproduced within one standard deviation across a wide portion of the minor radius. Experimental conditions are reproduced by ion scale simulations, without the need to include density and temperature profile curvature effects. The experimental case is used as baseline to predict that the non-dimensional confinement scaling in negative triangularity plasmas increases strongly with plasma current while slightly degrading at increasing normalized pressure and decreasing collisionality. Recent experiments showed that low toroidal rotation negatively impacts confinement; consistent with the experiment, simulations predict that low rotational shear significantly affects confinement unless the plasma effective charge is maintained above a minimum level. Core confinement is predicted to significantly degrade in low aspect ratio devices.
{"title":"Nonlinear gyrokinetic modelling of high confinement negative triangularity plasmas","authors":"A. Marinoni, M.E. Austin, J. Candy, C. Chrystal, S.R. Haskey, M. Porkolab, J.C. Rost and F. Scotti","doi":"10.1088/1741-4326/ad5a1c","DOIUrl":"https://doi.org/10.1088/1741-4326/ad5a1c","url":null,"abstract":"Nonlinear gyrokinetic simulations correctly predict particle as well as ion and electron energy fluxes of high confinement plasmas with a negative triangularity cross sectional shape, showing that core transport in these plasmas is well described by standard gyrokinetic models. Experimentally inferred power balance fluxes are mostly reproduced within one standard deviation across a wide portion of the minor radius. Experimental conditions are reproduced by ion scale simulations, without the need to include density and temperature profile curvature effects. The experimental case is used as baseline to predict that the non-dimensional confinement scaling in negative triangularity plasmas increases strongly with plasma current while slightly degrading at increasing normalized pressure and decreasing collisionality. Recent experiments showed that low toroidal rotation negatively impacts confinement; consistent with the experiment, simulations predict that low rotational shear significantly affects confinement unless the plasma effective charge is maintained above a minimum level. Core confinement is predicted to significantly degrade in low aspect ratio devices.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"19 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141530673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-27DOI: 10.1088/1741-4326/ad52a6
Haolong Li, Ping Zhu, Hang Li, Muquan Wu, Xiang Zhu and Jingting Luo
The safe operation of most tokamaks, especially the large ones, relies on the feedback control of vertical displacement events (VDEs). However, most of these feedback control systems are based on axisymmetric VDE models. In this study, we use NIMROD simulations to study the role of non-axisymmetric perturbations in free drift vertical displacement events on EAST. The high-n modes in the non-axisymmetric VDE grow first, which drives the formation of high-n magnetic island chains. Subsequently, the magnetic island chains grow and overlap with each other, leading to the destruction of the magnetic flux surface, which induces a minor disruption and accelerates the start of the following major disruption. The magnetic island and the stochastic magnetic field allow the toroidally non-axisymmetric poloidal plasma current to jet towards the hoop force direction, forming finger-like and filamentary structures. Such a plasma current non-axisymmetry strongly depends on the anisotropy in the thermal transport coefficients.
大多数托卡马克（尤其是大型托卡马克）的安全运行都依赖于对垂直位移事件（VDE）的反馈控制。然而，这些反馈控制系统大多基于轴对称 VDE 模型。在本研究中，我们使用 NIMROD 模拟来研究非轴对称扰动在 EAST 自由漂移垂直位移事件中的作用。非轴对称 VDE 中的高 n 模首先增长，这推动了高 n 磁岛链的形成。随后，磁岛链增长并相互重叠，导致磁通面破坏，从而引发小扰动，并加速了随后大扰动的开始。磁岛和随机磁场使得环状非轴对称极性等离子体电流向箍力方向喷射，形成指状和丝状结构。这种等离子体电流的非轴对称性在很大程度上取决于热传输系数的各向异性。
{"title":"Roles of non-axisymmetric perturbations in free drift vertical displacement events on EAST","authors":"Haolong Li, Ping Zhu, Hang Li, Muquan Wu, Xiang Zhu and Jingting Luo","doi":"10.1088/1741-4326/ad52a6","DOIUrl":"https://doi.org/10.1088/1741-4326/ad52a6","url":null,"abstract":"The safe operation of most tokamaks, especially the large ones, relies on the feedback control of vertical displacement events (VDEs). However, most of these feedback control systems are based on axisymmetric VDE models. In this study, we use NIMROD simulations to study the role of non-axisymmetric perturbations in free drift vertical displacement events on EAST. The high-n modes in the non-axisymmetric VDE grow first, which drives the formation of high-n magnetic island chains. Subsequently, the magnetic island chains grow and overlap with each other, leading to the destruction of the magnetic flux surface, which induces a minor disruption and accelerates the start of the following major disruption. The magnetic island and the stochastic magnetic field allow the toroidally non-axisymmetric poloidal plasma current to jet towards the hoop force direction, forming finger-like and filamentary structures. Such a plasma current non-axisymmetry strongly depends on the anisotropy in the thermal transport coefficients.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"8 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-27DOI: 10.1088/1741-4326/ad58f6
A.O. Nelson, D.T. Garnier, D.J. Battaglia, C. Paz-Soldan, I. Stewart, M. Reinke, A.J. Creely and J. Wai
To achieve its performance goals, SPARC plans to operate in equilibrium configurations with a strong elongation of , which in turn will destabilize the n = 0 vertical instability. However, SPARC also features a relatively thick conducting wall that is designed to withstand disruption forces, leading to lower vertical instability growth rates than usually encountered. In this work, we use the TokSyS framework to survey families of accessible shapes near the SPARC baseline configuration, finding maximum growth rates in the range of s−1. The addition of steel vertical stability plates has only a modest ( ) effect on reducing the vertical growth rate and almost no effect on the plasma controllability when the full vertical stability system is taken into account, providing flexibility in the plate conductivity in the SPARC design. Analysis of the maximum controllable displacement on SPARC is used to inform the power supply voltage and current limit requirements needed to control an initial vertical displacement of 5% of the minor radius. From the expected spectra of plasma disturbances and diagnostic noise, requirements for filter latency and vertical stability coil heating tolerances are also obtained. Small modifications to the outboard limiter location are suggested to allow for an unmitigated vertical disturbance as large as 5% of the minor radius without allowing the plasma to become limited. Further, investigations with the 3D COMSOL code reveal that strategic inclusion of insulating structures within the VSC supports are needed to maintain sufficient magnetic response. The workflows presented here help to establish a model for the integrated predictive design for future devices by coupling engineering decisions with physics needs.
{"title":"Implications of vertical stability control on the SPARC tokamak","authors":"A.O. Nelson, D.T. Garnier, D.J. Battaglia, C. Paz-Soldan, I. Stewart, M. Reinke, A.J. Creely and J. Wai","doi":"10.1088/1741-4326/ad58f6","DOIUrl":"https://doi.org/10.1088/1741-4326/ad58f6","url":null,"abstract":"To achieve its performance goals, SPARC plans to operate in equilibrium configurations with a strong elongation of , which in turn will destabilize the n = 0 vertical instability. However, SPARC also features a relatively thick conducting wall that is designed to withstand disruption forces, leading to lower vertical instability growth rates than usually encountered. In this work, we use the TokSyS framework to survey families of accessible shapes near the SPARC baseline configuration, finding maximum growth rates in the range of s−1. The addition of steel vertical stability plates has only a modest ( ) effect on reducing the vertical growth rate and almost no effect on the plasma controllability when the full vertical stability system is taken into account, providing flexibility in the plate conductivity in the SPARC design. Analysis of the maximum controllable displacement on SPARC is used to inform the power supply voltage and current limit requirements needed to control an initial vertical displacement of 5% of the minor radius. From the expected spectra of plasma disturbances and diagnostic noise, requirements for filter latency and vertical stability coil heating tolerances are also obtained. Small modifications to the outboard limiter location are suggested to allow for an unmitigated vertical disturbance as large as 5% of the minor radius without allowing the plasma to become limited. Further, investigations with the 3D COMSOL code reveal that strategic inclusion of insulating structures within the VSC supports are needed to maintain sufficient magnetic response. The workflows presented here help to establish a model for the integrated predictive design for future devices by coupling engineering decisions with physics needs.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"16 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141514859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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