Pub Date : 2024-05-29DOI: 10.1088/1361-6587/ad4d1d
A Balestri, J Ball, S Coda, D J Cruz-Zabala, M Garcia-Munoz and E Viezzer
In this work, we study the impact of aspect ratio (the ratio of major radius R0 to minor radius r) on the confinement benefits of negative triangularity (NT) plasma shaping. We use high-fidelity flux tube gyrokinetic GENE simulations and consider several different scenarios: four of them inspired by TCV experimental data, a scenario inspired by DIII-D experimental data and a scenario expected in the new SMART spherical tokamak. The present study reveals a distinct and non-trivial dependence. NT improves confinement at any value of A for ITG turbulence, while for TEM turbulence confinement is improved only in the case of large and conventional aspect ratios. Additionally, through a detailed study of a large aspect ratio case with pure ITG drive, we develop an intuitive physical picture that explains the beneficial effect of NT at large and conventional aspect ratios. This picture does not hold in TEM-dominated regimes, where a complex synergistic effect of many factors is found. Finally, we performed the first linear gyrokinetic simulations of SMART, finding that both NT and PT scenarios are dominated by micro-tearing-mode (MTM) turbulence and that NT is more susceptible to MTMs at tight aspect ratio. However, a regime where ITG dominates can be found in SMART, and in this regime NT is more linearly stable.
在这项工作中，我们研究了长宽比（主要半径 R0 与次要半径 r 之比）对负三角形（NT）等离子体整形的约束效益的影响。我们使用高保真通量管陀螺动能 GENE 仿真，并考虑了几种不同的情况：其中四种情况受到 TCV 实验数据的启发，一种情况受到 DIII-D 实验数据的启发，还有一种情况预计会出现在新的 SMART 球形托卡马克中。本研究揭示了一种明显的非三维依赖关系。对于 ITG 湍流，NT 在任何 A 值下都能提高约束性，而对于 TEM 湍流，只有在大纵横比和常规纵横比的情况下才能提高约束性。此外，通过对纯 ITG 驱动的大纵横比情况的详细研究，我们得出了一个直观的物理图景，解释了 NT 在大纵横比和常规纵横比情况下的有利影响。在以 TEM 为主导的情况下，这种图景并不成立，在这种情况下，许多因素会产生复杂的协同效应。最后，我们首次对 SMART 进行了线性陀螺动力学模拟，结果发现，NT 和 PT 两种情况都以微撕裂模式（MTM）湍流为主，而在狭长比情况下，NT 更容易受到 MTM 的影响。不过，在 SMART 中可以发现 ITG 占主导地位的情况，在这种情况下，NT 的线性稳定性更高。
{"title":"Physical insights from the aspect ratio dependence of turbulence in negative triangularity plasmas","authors":"A Balestri, J Ball, S Coda, D J Cruz-Zabala, M Garcia-Munoz and E Viezzer","doi":"10.1088/1361-6587/ad4d1d","DOIUrl":"https://doi.org/10.1088/1361-6587/ad4d1d","url":null,"abstract":"In this work, we study the impact of aspect ratio (the ratio of major radius R0 to minor radius r) on the confinement benefits of negative triangularity (NT) plasma shaping. We use high-fidelity flux tube gyrokinetic GENE simulations and consider several different scenarios: four of them inspired by TCV experimental data, a scenario inspired by DIII-D experimental data and a scenario expected in the new SMART spherical tokamak. The present study reveals a distinct and non-trivial dependence. NT improves confinement at any value of A for ITG turbulence, while for TEM turbulence confinement is improved only in the case of large and conventional aspect ratios. Additionally, through a detailed study of a large aspect ratio case with pure ITG drive, we develop an intuitive physical picture that explains the beneficial effect of NT at large and conventional aspect ratios. This picture does not hold in TEM-dominated regimes, where a complex synergistic effect of many factors is found. Finally, we performed the first linear gyrokinetic simulations of SMART, finding that both NT and PT scenarios are dominated by micro-tearing-mode (MTM) turbulence and that NT is more susceptible to MTMs at tight aspect ratio. However, a regime where ITG dominates can be found in SMART, and in this regime NT is more linearly stable.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"6 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141196722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-05-29DOI: 10.1088/1361-6587/ad4589
X Sáez, A Soba, J V Ylla Català, G Saxena, M Garcia-Gasulla, C Morales, D V Dorca, M Komm, A Podolnik, J Romazanov, E Sánchez, J L Velasco and M J Mantsinen
Several dedicated high-performance computing (HPC) centers provide essential expertise and support in developing a suitable portfolio of EUROfusion standard codes. Barcelona supercomputing center (BSC) is one of these HPC hubs involved in this complex task. Several fusion codes were selected, installed and analyzed to meet the developers’ requirements, ranging from portability to GPU, improving the performance, getting better data management, extending the capacity of coupling with other codes, etc. In this paper, we will describe the work developed by BSC and some of the tasks carried out in this project. We will explain briefly how the project is faced and the work required to create good quality codes, i.e. robust and trustable software capable of running efficiently in modern HPC systems.
{"title":"The Advanced Computing Hub at BSC: improving fusion codes following modern software engineering standards","authors":"X Sáez, A Soba, J V Ylla Català, G Saxena, M Garcia-Gasulla, C Morales, D V Dorca, M Komm, A Podolnik, J Romazanov, E Sánchez, J L Velasco and M J Mantsinen","doi":"10.1088/1361-6587/ad4589","DOIUrl":"https://doi.org/10.1088/1361-6587/ad4589","url":null,"abstract":"Several dedicated high-performance computing (HPC) centers provide essential expertise and support in developing a suitable portfolio of EUROfusion standard codes. Barcelona supercomputing center (BSC) is one of these HPC hubs involved in this complex task. Several fusion codes were selected, installed and analyzed to meet the developers’ requirements, ranging from portability to GPU, improving the performance, getting better data management, extending the capacity of coupling with other codes, etc. In this paper, we will describe the work developed by BSC and some of the tasks carried out in this project. We will explain briefly how the project is faced and the work required to create good quality codes, i.e. robust and trustable software capable of running efficiently in modern HPC systems.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"64 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141196331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-05-15DOI: 10.1088/1361-6587/ad48b7
Jinsu Kim, Jeongwon Lee, Jaemin Seo, Young-Chul Ghim, Yeongsun Lee and Yong-Su Na
In this research, we develop a data-driven disruption predictor based on Bayesian deep probabilistic learning, capable of predicting disruptions and modeling uncertainty in KSTAR. Unlike conventional neural networks within a frequentist approach, Bayesian neural networks can quantify the uncertainty associated with their predictions, thereby enhancing the precision of disruption prediction by mitigating false alarm rates through uncertainty thresholding. Leveraging 0D plasma parameters from EFIT and diagnostic data, a temporal convolutional network adept at handling multi-time scale data was utilized. The proposed framework demonstrates proficiency in predicting disruptions, substantiating its effectiveness through successful applications to KSTAR experimental data.
{"title":"Enhancing disruption prediction through Bayesian neural network in KSTAR","authors":"Jinsu Kim, Jeongwon Lee, Jaemin Seo, Young-Chul Ghim, Yeongsun Lee and Yong-Su Na","doi":"10.1088/1361-6587/ad48b7","DOIUrl":"https://doi.org/10.1088/1361-6587/ad48b7","url":null,"abstract":"In this research, we develop a data-driven disruption predictor based on Bayesian deep probabilistic learning, capable of predicting disruptions and modeling uncertainty in KSTAR. Unlike conventional neural networks within a frequentist approach, Bayesian neural networks can quantify the uncertainty associated with their predictions, thereby enhancing the precision of disruption prediction by mitigating false alarm rates through uncertainty thresholding. Leveraging 0D plasma parameters from EFIT and diagnostic data, a temporal convolutional network adept at handling multi-time scale data was utilized. The proposed framework demonstrates proficiency in predicting disruptions, substantiating its effectiveness through successful applications to KSTAR experimental data.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"53 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141061301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-05-15DOI: 10.1088/1361-6587/ad4740
N T Mitchell, D A Chapman, C J McDevitt, M P Read and G Kagan
A reduced kinetic method (RKM) with a first-principles collision operator is introduced in a 1D2V planar geometry and implemented in a computationally inexpensive code to investigate non-local ion heat transport in multi-species plasmas. The RKM successfully reproduces local results for multi-species ion systems and the important features expected to arise due to non-local effects on the heat flux are captured. In addition to this, novel features associated with multi-species, as opposed to single species, cases are found. Effects of non-locality on the heat flux are investigated in mass and charge symmetric and asymmetric ion mixtures with temperature, pressure, and concentration gradients. In particular, the enthalpy flux associated with diffusion is found to be insensitive to sharp pressure and concentration gradients, increasing its significance in comparison to the conductive heat flux driven by temperature gradients in non-local scenarios. The RKM code can be used for investigating other kinetic and non-local effects in a broader plasma physics context. Due to its relatively low computational cost it can also serve as a practical non-local ion heat flux closure in hydrodynamic simulations or as a training tool for machine learning surrogates.
{"title":"A reduced kinetic method for investigating non-local ion heat transport in ideal multi-species plasmas","authors":"N T Mitchell, D A Chapman, C J McDevitt, M P Read and G Kagan","doi":"10.1088/1361-6587/ad4740","DOIUrl":"https://doi.org/10.1088/1361-6587/ad4740","url":null,"abstract":"A reduced kinetic method (RKM) with a first-principles collision operator is introduced in a 1D2V planar geometry and implemented in a computationally inexpensive code to investigate non-local ion heat transport in multi-species plasmas. The RKM successfully reproduces local results for multi-species ion systems and the important features expected to arise due to non-local effects on the heat flux are captured. In addition to this, novel features associated with multi-species, as opposed to single species, cases are found. Effects of non-locality on the heat flux are investigated in mass and charge symmetric and asymmetric ion mixtures with temperature, pressure, and concentration gradients. In particular, the enthalpy flux associated with diffusion is found to be insensitive to sharp pressure and concentration gradients, increasing its significance in comparison to the conductive heat flux driven by temperature gradients in non-local scenarios. The RKM code can be used for investigating other kinetic and non-local effects in a broader plasma physics context. Due to its relatively low computational cost it can also serve as a practical non-local ion heat flux closure in hydrodynamic simulations or as a training tool for machine learning surrogates.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"5 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141061293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-05-13DOI: 10.1088/1361-6587/ad4672
Jianzhao Wang, Weiming An, Rong Tang, Weiyu Meng and Jiayong Zhong
The particle-in-cell (PIC) method has been widely used for studying plasma physics. However, fully three-dimensional PIC simulations always require huge computational resources. For problems with near azimuthal symmetry, recent work (Lifschitz et al 2009 J. Comput. Phys.228 1803–14, Davidson et al 2015 J. Comput. Phys.281 1063–77, Li et al 2021 Comput. Phys. Commun.261 107784, Li et al 2022 J. Comput. Phys.470 111599) has shown that expanding all the quantities defined on the grid in azimuthal harmonics and truncating the expansion can improve the code efficiency. In this paper, we describe a novel parallel algorithm for efficiently simulating three-dimensional near-spherical symmetry problems. Our approach expands all physical quantities in the and directions in spherical coordinates using vector spherical harmonics. The code is capable of simulating three-dimensional asymmetric scenarios by accurately tracking the evolution of distinct individual modes while preserving the charge conservation law. The fundamental dispersion relation of EM waves in the plasma has been obtained using VSHPIC simulation results. The code also shows a well strong scalability up to more than 1000 cores.
粒子入胞（PIC）方法已被广泛用于研究等离子体物理。然而，全三维 PIC 模拟总是需要巨大的计算资源。对于近乎方位对称的问题，最近的研究（Lifschitz et al 2009 J. Comput.Phys.228 1803-14, Davidson et al 2015 J. Comput.Phys.281 1063-77，Li 等人 2021 年 Comput.Phys.Commun.261 107784、Li 等人 2022 J. Comput.Phys.470 111599）表明，以方位谐波扩展网格上定义的所有量并截断扩展可以提高代码效率。本文介绍了一种高效模拟三维近球面对称问题的新型并行算法。我们的方法使用矢量球面谐波对球面坐标中和方向上的所有物理量进行扩展。该代码能够在保留电荷守恒定律的同时，准确跟踪不同单个模式的演变，从而模拟三维非对称场景。利用 VSHPIC 的模拟结果获得了等离子体中电磁波的基本色散关系。该代码还具有很强的可扩展性，可扩展至 1000 多个内核。
{"title":"VSHPIC: a particle-in-cell algorithm based on vector spherical harmonics expansion","authors":"Jianzhao Wang, Weiming An, Rong Tang, Weiyu Meng and Jiayong Zhong","doi":"10.1088/1361-6587/ad4672","DOIUrl":"https://doi.org/10.1088/1361-6587/ad4672","url":null,"abstract":"The particle-in-cell (PIC) method has been widely used for studying plasma physics. However, fully three-dimensional PIC simulations always require huge computational resources. For problems with near azimuthal symmetry, recent work (Lifschitz et al 2009 J. Comput. Phys.228 1803–14, Davidson et al 2015 J. Comput. Phys.281 1063–77, Li et al 2021 Comput. Phys. Commun.261 107784, Li et al 2022 J. Comput. Phys.470 111599) has shown that expanding all the quantities defined on the grid in azimuthal harmonics and truncating the expansion can improve the code efficiency. In this paper, we describe a novel parallel algorithm for efficiently simulating three-dimensional near-spherical symmetry problems. Our approach expands all physical quantities in the and directions in spherical coordinates using vector spherical harmonics. The code is capable of simulating three-dimensional asymmetric scenarios by accurately tracking the evolution of distinct individual modes while preserving the charge conservation law. The fundamental dispersion relation of EM waves in the plasma has been obtained using VSHPIC simulation results. The code also shows a well strong scalability up to more than 1000 cores.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"43 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140932010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-05-09DOI: 10.1088/1361-6587/ad4418
K Habib, M R Hassan, M S Alam, S Sultana
A magnetized nonthermal electron–positron-ion (e-p-i) plasma is considered to study the propagation properties of ion-acoustic solitary and shock waves in the presence of trapped positrons and electrons for the first time. The Schamel-κ (kappa) distribution function that describes plasma nonthermality and particle trapping is assumed to consider electrons and positrons. The diffusive effect of ion plasma fluid, which is responsible for shock dynamics, is taken into account. A nonlinear Schamel-Korteweg–de Vries-Burgers’ (SKdVB) equation is derived by employing the reductive perturbation approach, and the solitary and shock wave solutions of the SKdVB equation have also been derived for different limiting cases. It is found that only positive potential nonlinear structures (for both solitary and shock waves) are formed in the proposed plasma system. The condition for stable solitons in the absence of dissipation is analyzed, and the nature of arbitrary amplitude solitary waves (obtained via the Sagdeev potential approach) is discussed. It is found through theoretical and numerical investigation that different plasma compositional parameters (such as the trapping effect of electrons (βe) and positrons (βp), the obliquity effect (θ), electron-to-ion number density ratio (µe), the magnetic field effect (via Ω) and the viscous effect (via η)) have a significant influence on the dynamics of ion-acoustic solitary and shock waves. The theoretical and numerical investigations in this study may be helpful in describing the nature of localized structures in different plasma contexts, e.g. space and astrophysical plasmas and experimental plasmas where electron–positron-ion plasmas exist.
{"title":"An overview of ion-acoustic solitary and shock waves in a magnetized nonthermal plasma: influence of trapped positrons and electrons","authors":"K Habib, M R Hassan, M S Alam, S Sultana","doi":"10.1088/1361-6587/ad4418","DOIUrl":"https://doi.org/10.1088/1361-6587/ad4418","url":null,"abstract":"A magnetized nonthermal electron–positron-ion (e-p-i) plasma is considered to study the propagation properties of ion-acoustic solitary and shock waves in the presence of trapped positrons and electrons for the first time. The Schamel-<italic toggle=\"yes\">κ</italic> (kappa) distribution function that describes plasma nonthermality and particle trapping is assumed to consider electrons and positrons. The diffusive effect of ion plasma fluid, which is responsible for shock dynamics, is taken into account. A nonlinear Schamel-Korteweg–de Vries-Burgers’ (SKdVB) equation is derived by employing the reductive perturbation approach, and the solitary and shock wave solutions of the SKdVB equation have also been derived for different limiting cases. It is found that only positive potential nonlinear structures (for both solitary and shock waves) are formed in the proposed plasma system. The condition for stable solitons in the absence of dissipation is analyzed, and the nature of arbitrary amplitude solitary waves (obtained via the Sagdeev potential approach) is discussed. It is found through theoretical and numerical investigation that different plasma compositional parameters (such as the trapping effect of electrons (<italic toggle=\"yes\">β</italic>\u0000<sub>\u0000<italic toggle=\"yes\">e</italic>\u0000</sub>) and positrons (<italic toggle=\"yes\">β</italic>\u0000<sub>\u0000<italic toggle=\"yes\">p</italic>\u0000</sub>), the obliquity effect (<italic toggle=\"yes\">θ</italic>), electron-to-ion number density ratio (<italic toggle=\"yes\">µ</italic>\u0000<sub>\u0000<italic toggle=\"yes\">e</italic>\u0000</sub>), the magnetic field effect (via Ω) and the viscous effect (via <italic toggle=\"yes\">η</italic>)) have a significant influence on the dynamics of ion-acoustic solitary and shock waves. The theoretical and numerical investigations in this study may be helpful in describing the nature of localized structures in different plasma contexts, e.g. space and astrophysical plasmas and experimental plasmas where electron–positron-ion plasmas exist.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"43 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140932094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-05-09DOI: 10.1088/1361-6587/ad44d6
Grant Rutherford, Samuel J Frank, Andrew H Seltzman, Paul T Bonoli, Stephen J Wukitch
High field side lower hybrid current drive (LHCD) is one potential candidate for efficient non-inductive current drive in tokamak power plants, and the first test of this technology will occur on the DIII-D tokamak during the 2024 campaign. Previous LFS launch experiments operated in the multi-pass regime and relied on scrape-off layer interactions to close the spectral gap. In the DIII-D experiment, single-pass damping is achievable via an upshift in the parallel refractive index N∥ caused by mode converting twice (slow → fast → slow). This mode conversion affects the ray trajectories and can lead to enhanced N∥ upshift depending on where mode conversion occurs. Compared to multi-pass absorption experiments, the optimization of launched N∥ and plasma parameters can be counter-intuitive: increased density may increase efficiency and smaller N∥,launch tend to damp closer to the separatrix. A hard x-ray camera installed to measure the bremsstrahlung (50–250 keV) radiation from LHCD-generated fast electrons is capable of verifying the trends reporting in this paper through comparison to the ray-tracing/Fokker–Planck codes GENRAY/CQL3D.
{"title":"Optimization of the N∥ Upshift in the DIII-D high field side lower hybrid current drive experiment","authors":"Grant Rutherford, Samuel J Frank, Andrew H Seltzman, Paul T Bonoli, Stephen J Wukitch","doi":"10.1088/1361-6587/ad44d6","DOIUrl":"https://doi.org/10.1088/1361-6587/ad44d6","url":null,"abstract":"High field side lower hybrid current drive (LHCD) is one potential candidate for efficient non-inductive current drive in tokamak power plants, and the first test of this technology will occur on the DIII-D tokamak during the 2024 campaign. Previous LFS launch experiments operated in the multi-pass regime and relied on scrape-off layer interactions to close the spectral gap. In the DIII-D experiment, single-pass damping is achievable via an upshift in the parallel refractive index <inline-formula>\u0000<tex-math><?CDATA $N_parallel$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>N</mml:mi><mml:mo>∥</mml:mo></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad44d6ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> caused by mode converting twice (slow <inline-formula>\u0000<tex-math><?CDATA $rightarrow$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mo stretchy=\"false\">→</mml:mo></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad44d6ieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> fast <inline-formula>\u0000<tex-math><?CDATA $rightarrow$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mo stretchy=\"false\">→</mml:mo></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad44d6ieqn4.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> slow). This mode conversion affects the ray trajectories and can lead to enhanced <inline-formula>\u0000<tex-math><?CDATA $N_parallel$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>N</mml:mi><mml:mo>∥</mml:mo></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad44d6ieqn5.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> upshift depending on where mode conversion occurs. Compared to multi-pass absorption experiments, the optimization of launched <inline-formula>\u0000<tex-math><?CDATA $N_parallel$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>N</mml:mi><mml:mo>∥</mml:mo></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad44d6ieqn6.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> and plasma parameters can be counter-intuitive: increased density may increase efficiency and smaller <inline-formula>\u0000<tex-math><?CDATA $N_{parallel,mathrm{launch}}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>N</mml:mi><mml:mrow><mml:mo>∥</mml:mo><mml:mo>,</mml:mo><mml:mrow><mml:mi>launch</mml:mi></mml:mrow></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad44d6ieqn7.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> tend to damp closer to the separatrix. A hard x-ray camera installed to measure the bremsstrahlung (50–250 keV) radiation from LHCD-generated fast electrons is capable of verifying the trends reporting in this paper through comparison to the ray-tracing/Fokker–Planck codes GENRAY/CQL3D.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"105 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140932095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-05-09DOI: 10.1088/1361-6587/ad4486
J Rueda-Rueda, M Garcia-Munoz, E Viezzer, P A Schneider, P Oyola, J Galdon-Quiroga, M Salewski, B S Schmidt, J Garcia-Dominguez, ASDEX Upgrade team4
In this paper we demonstrate how the inversion, in energy and major radius (E, R) coordinates, of imaging neutral particle analyser (INPA) measurements can be used to obtain the fast-ion distribution. The INPA is most sensitive to passing ions with energies in the range (20–150) keV and pitches near 0.5 in the core and 0.7 near the plasma edge. Inversion of synthetic signals, via 0th-order Tikhonov and Elastic Net regularization, were performed to demonstrate the capability of recovering the ground truth fast-ion 2D phase-space distribution resolved in major radius and energy, even in the presence of moderate noise levels (10%). Finally, we apply our method to measure the 2D phase-space distribution in an MHD quiescent plasma at ASDEX Upgrade and find good agreement with the slowing down fast-ion distribution predicted by TRANSP.
{"title":"Tomographic reconstructions of the fast-ion phase space using imaging neutral particle analyser measurements","authors":"J Rueda-Rueda, M Garcia-Munoz, E Viezzer, P A Schneider, P Oyola, J Galdon-Quiroga, M Salewski, B S Schmidt, J Garcia-Dominguez, ASDEX Upgrade team4","doi":"10.1088/1361-6587/ad4486","DOIUrl":"https://doi.org/10.1088/1361-6587/ad4486","url":null,"abstract":"In this paper we demonstrate how the inversion, in energy and major radius (E, R) coordinates, of imaging neutral particle analyser (INPA) measurements can be used to obtain the fast-ion distribution. The INPA is most sensitive to passing ions with energies in the range (20–150) keV and pitches near 0.5 in the core and 0.7 near the plasma edge. Inversion of synthetic signals, via 0th-order Tikhonov and Elastic Net regularization, were performed to demonstrate the capability of recovering the ground truth fast-ion 2D phase-space distribution resolved in major radius and energy, even in the presence of moderate noise levels (10%). Finally, we apply our method to measure the 2D phase-space distribution in an MHD quiescent plasma at ASDEX Upgrade and find good agreement with the slowing down fast-ion distribution predicted by TRANSP.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"105 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140932007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-05-09DOI: 10.1088/1361-6587/ad441b
T Fu, X Q Wang, X Su, Y Xu, S Okamura, A Shimizu, M Isobe, J Cheng, H F Liu, J Huang, X Zhang, H Liu, C J Tang
In a quasi-axisymmetric stellarator, a significant bootstrap current will result in the generation of low-order rational surfaces and three-dimensional (3D) magnetic islands. In this paper, the influence of plasma density profiles on the equilibrium magnetic islands for the Chinese first quasi-axisymmetric stellarator (CFQS) is investigated using the HINT code. It is found that the flattening of the core plasma density profile leads to a significant suppression of magnetic islands. When the peaking factor of plasma density is 1.19, complete suppression of magnetic islands occurs while maintaining excellent integrity of the magnetic surface even with the volume-averaged plasma beta <β> increase up to 2%. On the other hand, during the transition of a plasma density profile from flat to hollow, there is a reversal in the core bootstrap current, resulting in reduction of rotational transform values to pass through the rational surface. Hence, formation of magnetic islands in the core region. Therefore, effective inhibition of CFQS’s magnetic islands can be achieved by appropriately controlling density profiles through methods like gas injection.
在准轴对称恒星器中，巨大的自举电流将导致低阶有理面和三维（3D）磁岛的产生。本文利用 HINT 代码研究了等离子体密度剖面对中国第一个准轴对称恒星器（CFQS）平衡磁岛的影响。研究发现，核心等离子体密度剖面的扁平化会显著抑制磁岛的产生。当等离子体密度的峰值因子为 1.19 时，磁岛被完全抑制，同时磁表面保持良好的完整性，即使等离子体的体积平均贝塔值增加到 2%。另一方面，在等离子体密度剖面从扁平向中空过渡期间，磁芯自举电流会发生逆转，导致通过合理表面的旋转变换值减少。因此，在磁芯区域形成了磁岛。因此，可以通过气体注入等方法适当控制密度剖面，从而有效抑制 CFQS 的磁岛。
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Pub Date : 2024-05-08DOI: 10.1088/1361-6587/ad441c
Q Xia, D Moulton, J Omotani, F Militello
Tokamak edge turbulence is crucial for the cross-field transport of particles and energy away from the separatrix. A better understanding of what affects the turbulence helps to control the heat flux to the divertor targets and the wall. One potentially important factor is the ion particle source in the divertor, as the neutral pathways and the ionisation source distributions are different depending on the divertor geometry, e.g. vertical- and horizontal-target configurations. Numerically, how to represent the sources and mimic the effects on the SOL in the simulations is still an open question. In this paper, we use a 3D turbulence code STORM, based on drift-reduced Braginskii equations, to study the effects of the divertor particle source distribution on turbulence in a simplified 3D slab geometry. The results show that it requires a large amount of divertor particle source to be peaked near the separatrix to alter the heat flux deposited on the target in attached conditions. This large non-uniform particle source can locally enhance the turbulence in the divertor volume, which redistributes the energy flux to the target and reduces the maximum amplitude. Meanwhile, the plasma profiles evaluated at the outboard midplane, such as the amplitudes and fluctuations of the density and temperature, are marginally changed. Another consequence of our results is that the prediction of the temperature difference between the outboard midplane and the target would be underestimated, if the calculation only considers the conductive heat flux and ignores this enhanced cross-field transport in the divertor.
托卡马克边缘湍流对于粒子和能量离开分离矩阵的跨场传输至关重要。更好地了解湍流的影响因素有助于控制流向分流器目标和壁面的热通量。一个潜在的重要因素是分流器中的离子粒子源，因为中性路径和电离源分布因分流器的几何形状（如垂直和水平靶配置）而异。从数值上讲，如何在模拟中表示电离源并模拟其对 SOL 的影响仍是一个未决问题。在本文中，我们使用基于漂移还原布拉金斯基方程的三维湍流代码 STORM，研究了分流器粒子源分布对简化三维板状几何中湍流的影响。结果表明，要改变附着条件下沉积在目标上的热通量，需要大量的分流粒子源在分离矩阵附近达到峰值。这种大量的非均匀粒子源可以局部增强分流器体积内的湍流，从而重新分配目标上的能量通量并减小最大振幅。同时，在外侧中平面评估的等离子体剖面，如密度和温度的振幅和波动，变化不大。我们研究结果的另一个结果是，如果计算时只考虑传导热通量而忽略了分流器中增强的跨场传输，那么外侧中平面与目标之间的温差预测值就会被低估。
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