Pub Date : 2024-01-09DOI: 10.1088/1741-4326/ad1c92
Kedong Li, Rong Wang, Zhongshi Yang, Kai Wu, Tao He, G. Jia, Xin Lin, L. Meng, Lin Yu, Bin Zhang, Jinhua Wu, Yanmin Duan, Songtao Mao, Qing Zang, Ling Zhang, Tao Zhang, Fudi Wang, Shouxin Wang, Q. Yuan, Liang Wang, Guang-Nan Luo
It is necessary for future fusion reactor to reduce the heat fluxes on the entire divertor target, especially if view of long pulse high performance operation. In recent EAST experiments, partial energy detachment without confinement degradation, and deep energy detachment with protection of the entire divertor target have both been confirmed on EAST corner slot divertor by argon (Ar) seeding, which can provide reference for the divertor protection on future fusion reactors. In the deep energy detachment state, the electron temperature Tet along entire lower outer divertor target decreases to less than 10 eV and heat fluxes are also strongly mitigated with peak heat flux reduction of more than 90%. Compared to the attached state, there is a moderate confinement degradation with H98,y2 from ~1 to ~0.9 because of Ar radiation in the core region. This confinement degradation can be avoided in the partial energy detachment state, where the radiative power losses in the core are reduced. The experiment and SOLPS-ITER simulation results show that there is no decrease of particle flux js on the divertor target in the partial energy detachment state because the momentum loss in the SOL region is not strong enough. With increasing Ar seeding, there is a js decrease in the deep energy detachment state. The increases of momentum and power losses in the SOL region, and the decrease of upstream pressure all contribute to the js reduction.
未来的核聚变反应堆必须降低整个岔道靶上的热通量，特别是考虑到长脉冲的高性能运行。在最近的EAST实验中，通过氩（Ar）播种在EAST角槽分流器上证实了部分能量脱离而不会导致约束退化，以及深度能量脱离并保护整个分流器靶，这可以为未来聚变堆的分流器保护提供参考。在深能量脱离状态下，整个下部外岔道靶的电子温度Tet降低到10 eV以下，热通量也得到有力缓解，峰值热通量降低了90%以上。与附着状态相比，由于核心区域的氩辐射，H98,y2 会从 ~1 降至 ~0.9，从而导致适度的约束退化。在部分能量脱离状态下，这种约束性下降是可以避免的，因为在这种状态下，堆芯中的辐射功率损失会减少。实验和 SOLPS-ITER 模拟结果表明，在部分能量脱离状态下，由于 SOL 区域的动量损耗不够强大，分流靶上的粒子通量 js 不会减少。随着 Ar 加入量的增加，在深层能量分离状态下，粒子通量 js 有所下降。SOL 区域动量损失和功率损失的增加以及上游压力的降低都有助于 js 的降低。
{"title":"Comparison of partial and deep energy detachment behaviors with Ar seeding on EAST new corner slot divertor","authors":"Kedong Li, Rong Wang, Zhongshi Yang, Kai Wu, Tao He, G. Jia, Xin Lin, L. Meng, Lin Yu, Bin Zhang, Jinhua Wu, Yanmin Duan, Songtao Mao, Qing Zang, Ling Zhang, Tao Zhang, Fudi Wang, Shouxin Wang, Q. Yuan, Liang Wang, Guang-Nan Luo","doi":"10.1088/1741-4326/ad1c92","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1c92","url":null,"abstract":"\u0000 It is necessary for future fusion reactor to reduce the heat fluxes on the entire divertor target, especially if view of long pulse high performance operation. In recent EAST experiments, partial energy detachment without confinement degradation, and deep energy detachment with protection of the entire divertor target have both been confirmed on EAST corner slot divertor by argon (Ar) seeding, which can provide reference for the divertor protection on future fusion reactors. In the deep energy detachment state, the electron temperature Tet along entire lower outer divertor target decreases to less than 10 eV and heat fluxes are also strongly mitigated with peak heat flux reduction of more than 90%. Compared to the attached state, there is a moderate confinement degradation with H98,y2 from ~1 to ~0.9 because of Ar radiation in the core region. This confinement degradation can be avoided in the partial energy detachment state, where the radiative power losses in the core are reduced. The experiment and SOLPS-ITER simulation results show that there is no decrease of particle flux js on the divertor target in the partial energy detachment state because the momentum loss in the SOL region is not strong enough. With increasing Ar seeding, there is a js decrease in the deep energy detachment state. The increases of momentum and power losses in the SOL region, and the decrease of upstream pressure all contribute to the js reduction.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"40 25","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139442496","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 : 2024-01-09DOI: 10.1088/1741-4326/ad1c94
Tong Liu, Zheng-Xiong Wang, Lai Wei, Jialei Wang, Allan H Reiman
The radio frequency current condensation effect reported in [Reiman et al. PRL (2018)] is modelled in the nonlinear resistive magnetohydrodynamic (MHD) code. A series of numerical investigations have been performed to investigate the enhancement of electron cyclotron current drive (ECCD) by the current condensation effect during the control of neoclassical tearing mode (NTM) in tokamak plasmas. In the numerical model, both the parallel transport and the perpendicular transport of electron temperature are considered. The EC driven current and driven perturbed electron temperature can nonlinearly evolve within the given magnetic configuration and eventually reach saturation states. The input power threshold of ECCD and the fold bifurcation phenomenon are numerically verified via nonlinear simulations. The numerical results show good agreements with the analytical results. Moreover, spatial distributions of EC current for the two solutions at different condensed level are displayed. The control effectiveness of ECCD for large NTM islands has been evaluated while considering the current condensation effect. While taking into account current condensation effect, for a sufficiently large input power, a larger island can be more effectively stabilized than a smaller one, which suggests a reassessment of the previous idea that the ECCD should always be turned on as early as possible. The potential physics mechanism behind the ECCD control have all been discussed in detail. Furthermore, the condensation effect is found to have favorable effects on the radial misalignment of ECCD. In the consideration of the situation for extremely localized control needs, a highly peaking heating profile is adopted to verify that the fold bifurcation phenomenon still exists and the current condensation effect can still take effect in this extreme condition.
{"title":"Enhancement of ECCD by the current condensation effect for stabilizing large magnetic islands caused by neoclassical tearing modes in tokamak plasmas","authors":"Tong Liu, Zheng-Xiong Wang, Lai Wei, Jialei Wang, Allan H Reiman","doi":"10.1088/1741-4326/ad1c94","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1c94","url":null,"abstract":"\u0000 The radio frequency current condensation effect reported in [Reiman et al. PRL (2018)] is modelled in the nonlinear resistive magnetohydrodynamic (MHD) code. A series of numerical investigations have been performed to investigate the enhancement of electron cyclotron current drive (ECCD) by the current condensation effect during the control of neoclassical tearing mode (NTM) in tokamak plasmas. In the numerical model, both the parallel transport and the perpendicular transport of electron temperature are considered. The EC driven current and driven perturbed electron temperature can nonlinearly evolve within the given magnetic configuration and eventually reach saturation states. The input power threshold of ECCD and the fold bifurcation phenomenon are numerically verified via nonlinear simulations. The numerical results show good agreements with the analytical results. Moreover, spatial distributions of EC current for the two solutions at different condensed level are displayed. The control effectiveness of ECCD for large NTM islands has been evaluated while considering the current condensation effect. While taking into account current condensation effect, for a sufficiently large input power, a larger island can be more effectively stabilized than a smaller one, which suggests a reassessment of the previous idea that the ECCD should always be turned on as early as possible. The potential physics mechanism behind the ECCD control have all been discussed in detail. Furthermore, the condensation effect is found to have favorable effects on the radial misalignment of ECCD. In the consideration of the situation for extremely localized control needs, a highly peaking heating profile is adopted to verify that the fold bifurcation phenomenon still exists and the current condensation effect can still take effect in this extreme condition.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"44 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139442488","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 : 2024-01-05DOI: 10.1088/1741-4326/ad1b94
Yi Zhang, Zhibin Guo, R. R. Ma, Min Xu
We present an analytical model to evaluate the triangularity-shaping effects in accessing the second stable region for the ideal ballooning mode. Our results indicate that if the triangularity is sufficiently negative, the path from the first to the second stable region will be closed. The reason is that negative triangularity can weaken the stabilizing effect of the ``magnetic well", and even convert the ``magnetic well" into a ``magnetic hill", which will destabilize the ballooning mode. We also show that the synergistic effects of elongation, inverse aspect ratio, and safety factor can reopen the path to the second stable region. Through a variational approach, we derive an analytical expression of the critical negative triangularity for closing the access to the second stable region. Furthermore, our analysis reveals that in the second ballooning stable regime, the negative triangularity tends to inhibit the emergence of quasi marginally stable discrete Alfvén eigenmodes. These findings provide a quantitative understanding of how the negative triangularity configuration impacts the confinement of tokamak plasmas.
{"title":"An analytical model of how the negative triangularity cuts off the access to the second stable region in tokamak plasmas","authors":"Yi Zhang, Zhibin Guo, R. R. Ma, Min Xu","doi":"10.1088/1741-4326/ad1b94","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1b94","url":null,"abstract":"\u0000 We present an analytical model to evaluate the triangularity-shaping effects in accessing the second stable region for the ideal ballooning mode. Our results indicate that if the triangularity is sufficiently negative, the path from the first to the second stable region will be closed. The reason is that negative triangularity can weaken the stabilizing effect of the ``magnetic well\", and even convert the ``magnetic well\" into a ``magnetic hill\", which will destabilize the ballooning mode. We also show that the synergistic effects of elongation, inverse aspect ratio, and safety factor can reopen the path to the second stable region. Through a variational approach, we derive an analytical expression of the critical negative triangularity for closing the access to the second stable region. Furthermore, our analysis reveals that in the second ballooning stable regime, the negative triangularity tends to inhibit the emergence of quasi marginally stable discrete Alfvén eigenmodes. These findings provide a quantitative understanding of how the negative triangularity configuration impacts the confinement of tokamak plasmas.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"51 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381624","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 : 2024-01-04DOI: 10.1088/1741-4326/ad1af7
Pengjuan Su, Heng Lan, Chu Zhou, Jian Bao, A. Liu, Xiang Zhu, Mingfu Wu, Chenxi Luo, Jiangyue Han, Jialei Wang, Haiqing Liu, Tao Zhang, Ruijie Zhou, Shiyao Lin, Hailing Zhao, Youwen Sun, Z. Qiu, N. Chu, T. Tang, Yi Tan, Long Zeng, Zhe Gao
A series of high-frequency (400~1000 kHz) bursting core-localized Alfvén instabilities have been observed during ohmic discharges in EAST tokamak. The instability trigger favours the discharge conditions of low toroidal magnetic field and low electron density. The toroidal mode numbers are mainly n=2~3 and they propagate in the ion diamagnetic drift (co-current) direction. These modes are radially localized in the range of ρ_tor=0.2~0.35 based on Doppler BackScatter (DBS) measurement. They are identified as ellipticity-induced Alfvén eigenmodes (EAEs) occurring at q=1 rational surfaces by magnetohydrodynamics (MHD) simulations using the realistic geometry and plasma profiles. The EAEs show regular bursts with ~10 milliseconds duration along with the mode frequency chirping downwards and upwards rapidly. It is also found that sawtooth events can interrupt the growth and evolution of the EAEs, causing the modes to disappear immediately. Passing energetic electrons (EEs) that move much faster than Alfvén velocity are responsible for the destabilization of these EAEs, which attribute to the fact that the large poloidal and toroidal frequencies mostly cancel each other and satisfy the EAE resonance condition with primary energy exchange. These novel experimental results of the wave-particle interaction between EAEs and EEs are helpful for extrapolating alpha particle physics that are characterized by small orbit width with respect to machine size in future fusion reactors.
{"title":"Bursting core-localized ellipticity-induced Alfvén eigenmodes driven by energetic electrons during EAST ohmic discharges","authors":"Pengjuan Su, Heng Lan, Chu Zhou, Jian Bao, A. Liu, Xiang Zhu, Mingfu Wu, Chenxi Luo, Jiangyue Han, Jialei Wang, Haiqing Liu, Tao Zhang, Ruijie Zhou, Shiyao Lin, Hailing Zhao, Youwen Sun, Z. Qiu, N. Chu, T. Tang, Yi Tan, Long Zeng, Zhe Gao","doi":"10.1088/1741-4326/ad1af7","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1af7","url":null,"abstract":"\u0000 A series of high-frequency (400~1000 kHz) bursting core-localized Alfvén instabilities have been observed during ohmic discharges in EAST tokamak. The instability trigger favours the discharge conditions of low toroidal magnetic field and low electron density. The toroidal mode numbers are mainly n=2~3 and they propagate in the ion diamagnetic drift (co-current) direction. These modes are radially localized in the range of ρ_tor=0.2~0.35 based on Doppler BackScatter (DBS) measurement. They are identified as ellipticity-induced Alfvén eigenmodes (EAEs) occurring at q=1 rational surfaces by magnetohydrodynamics (MHD) simulations using the realistic geometry and plasma profiles. The EAEs show regular bursts with ~10 milliseconds duration along with the mode frequency chirping downwards and upwards rapidly. It is also found that sawtooth events can interrupt the growth and evolution of the EAEs, causing the modes to disappear immediately. Passing energetic electrons (EEs) that move much faster than Alfvén velocity are responsible for the destabilization of these EAEs, which attribute to the fact that the large poloidal and toroidal frequencies mostly cancel each other and satisfy the EAE resonance condition with primary energy exchange. These novel experimental results of the wave-particle interaction between EAEs and EEs are helpful for extrapolating alpha particle physics that are characterized by small orbit width with respect to machine size in future fusion reactors.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"50 24","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139385796","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 : 2024-01-04DOI: 10.1088/1741-4326/ad1af6
J. Cazabonne, S. Coda, Joan Decker, O. Krutkin, Umesh Kumar, Yves Savoye-Peysson
Electron-Cyclotron waves are a tool commonly used in tokamaks, in particular to drive current. Their ability to drive current in a very localized manner renders them an optimal tool for MHD mode mitigation. However, such applications require high accuracy and good control of the power deposition location to efficiently target the magnetic islands. It has been indirectly observed that the suprathermal electron distribution, resulting from the wave absorption, is broader than what is expected from experimentally-constrained forward drift-kinetic modeling. The present paper explores the possibility that beam scattering through the turbulent edge of the plasma may explain this observed discrepancy. In particular, full-wave studies exhibit three beam broadening regimes, from superdiffusive to diffusive, with an intermediate regime characterized by a Lorentzian beam profile with a slightly increased full-width at half maximum with respect to the quiet plasma case. In the Tokamak à Configuration Variable, dedicated plasma scenarios have been developed to test this hypothesis. A realistic worst-case fluctuation scenario falls into this intermediate beam broadening regime. By comparing the experimental hard X-ray emission from suprathermal electron Bremmstrahlung with the emission calculated by coupling a full-wave model to a Fokker-Planck solver, it is shown that that, in the tested cases, the beam broadening is not sufficient to explain the aforementioned discrepancy between simulation and experiment and that another mechanism must play the main role in broadening the suprathermal electron distribution.
电子-回旋加速器波是托卡马克中常用的一种工具，特别是用于驱动电流。电子-环电子波能够以非常局部的方式驱动电流，因此是减缓 MHD 模式的最佳工具。然而，这种应用需要高精度和良好的功率沉积位置控制，以便有效地瞄准磁岛。据间接观察，波吸收产生的过热电子分布比实验约束的前向漂移动力学建模所预期的要宽。本文探讨了通过等离子体湍流边缘的光束散射可能解释这种观察到的差异的可能性。特别是，全波研究显示了从超扩散到扩散的三种光束展宽机制，中间机制的特征是洛伦兹光束轮廓，与静态等离子体情况相比，半最大全宽略有增加。在托卡马克 à 配置变量中，开发了专门的等离子体方案来测试这一假设。现实中最糟糕的波动情况就属于这种中间光束展宽机制。通过比较实验中超热电子布赖姆斯特拉发射的硬 X 射线辐射和全波模型与福克-普朗克求解器耦合计算的辐射，结果表明，在测试的情况下，光束增宽不足以解释上述模拟与实验之间的差异，另一种机制必须在增宽超热电子分布方面发挥主要作用。
{"title":"Impact of microwave beam scattering by density fluctuations on the Electron-Cyclotron power deposition profile in tokamaks","authors":"J. Cazabonne, S. Coda, Joan Decker, O. Krutkin, Umesh Kumar, Yves Savoye-Peysson","doi":"10.1088/1741-4326/ad1af6","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1af6","url":null,"abstract":"\u0000 Electron-Cyclotron waves are a tool commonly used in tokamaks, in particular to drive current. Their ability to drive current in a very localized manner renders them an optimal tool for MHD mode mitigation. However, such applications require high accuracy and good control of the power deposition location to efficiently target the magnetic islands. It has been indirectly observed that the suprathermal electron distribution, resulting from the wave absorption, is broader than what is expected from experimentally-constrained forward drift-kinetic modeling. The present paper explores the possibility that beam scattering through the turbulent edge of the plasma may explain this observed discrepancy. In particular, full-wave studies exhibit three beam broadening regimes, from superdiffusive to diffusive, with an intermediate regime characterized by a Lorentzian beam profile with a slightly increased full-width at half maximum with respect to the quiet plasma case. In the Tokamak à Configuration Variable, dedicated plasma scenarios have been developed to test this hypothesis. A realistic worst-case fluctuation scenario falls into this intermediate beam broadening regime. By comparing the experimental hard X-ray emission from suprathermal electron Bremmstrahlung with the emission calculated by coupling a full-wave model to a Fokker-Planck solver, it is shown that that, in the tested cases, the beam broadening is not sufficient to explain the aforementioned discrepancy between simulation and experiment and that another mechanism must play the main role in broadening the suprathermal electron distribution.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"43 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384942","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 : 2024-01-04DOI: 10.1088/1741-4326/ad1af5
C. Michoski, Todd A Oliver, D. Hatch, Ahmed Diallo, M. Kotschenreuther, D. Eldon, Matthew Waller, R. Groebner, Andrew Oakleigh Nelson
Extracting reliable information from diagnostic data in tokamaks is critical for understanding, analyzing, and controlling the behavior of fusion plasmas and validating models describing that behavior. Recent interest within the fusion community has focused on the use of principled statistical methods, such as Gaussian Process Regression (GPR), to attempt to develop sharper, more reliable, and more rigorous tools for examining the complex observed behavior in these systems. While GPR is an enormously powerful tool, there is also the danger of drawing fragile, or inconsistent conclusions from naive GPR fits that are not driven by principled treatments. Here we review the fundamental concepts underlying GPR in a way that may be useful for broad-ranging applications in fusion science. We also revisit how GPR is developed for profile fitting in tokamaks. We examine various extensions and targeted modifications applicable to experimental observations in the edge of the DIII-D tokamak. Finally, we discuss best practices for applying GPR to fusion data.
{"title":"A Gaussian Process Guide for Signal Regression in Magnetic Fusion","authors":"C. Michoski, Todd A Oliver, D. Hatch, Ahmed Diallo, M. Kotschenreuther, D. Eldon, Matthew Waller, R. Groebner, Andrew Oakleigh Nelson","doi":"10.1088/1741-4326/ad1af5","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1af5","url":null,"abstract":"\u0000 Extracting reliable information from diagnostic data in tokamaks is critical for understanding, analyzing, and controlling the behavior of fusion plasmas and validating models describing that behavior. Recent interest within the fusion community has focused on the use of principled statistical methods, such as Gaussian Process Regression (GPR), to attempt to develop sharper, more reliable, and more rigorous tools for examining the complex observed behavior in these systems. While GPR is an enormously powerful tool, there is also the danger of drawing fragile, or inconsistent conclusions from naive GPR fits that are not driven by principled treatments. Here we review the fundamental concepts underlying GPR in a way that may be useful for broad-ranging applications in fusion science. We also revisit how GPR is developed for profile fitting in tokamaks. We examine various extensions and targeted modifications applicable to experimental observations in the edge of the DIII-D tokamak. Finally, we discuss best practices for applying GPR to fusion data.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"4 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384363","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 : 2024-01-04DOI: 10.1088/1741-4326/ad1af4
R. J. Zabolockis, Matiss Sondars, G. Vaivars, I. Reinholds, Vladimir Gostillo, Vladislav Malgin, Anton Kizilov, A. Lescinskis, Andrei Felsharuk, L. Avotina, A. S. Teimane, E. Sprugis, E. Pajuste
In this study, tritium enrichment system in a water phase has been developed based on the combination of a proton exchange membrane (PEM) electrolysis cell and fuel cell. As a PEM NafionTM and laboratory synthesized sulfonated poly ether ether ketone membranes modified with additional graphene layer in order to enhance tritium separation factor was used. Both differences in the kinetics of the hydrogen evolution reaction and transport through the graphene layer of different isotopes are the driving factors expecting to affect the separation of hydrogen isotopes. The separation factor was measured both during the electrolysis and fuel cell stage by using different membranes. The facilitating effect of the graphene on the separation efficiency was determined during the study. Separation factor obtained by the proposed method was evidently higher than by other conventional methods.
{"title":"Graphene-based electrochemical system for tritium enrichment","authors":"R. J. Zabolockis, Matiss Sondars, G. Vaivars, I. Reinholds, Vladimir Gostillo, Vladislav Malgin, Anton Kizilov, A. Lescinskis, Andrei Felsharuk, L. Avotina, A. S. Teimane, E. Sprugis, E. Pajuste","doi":"10.1088/1741-4326/ad1af4","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1af4","url":null,"abstract":"\u0000 In this study, tritium enrichment system in a water phase has been developed based on the combination of a proton exchange membrane (PEM) electrolysis cell and fuel cell. As a PEM NafionTM and laboratory synthesized sulfonated poly ether ether ketone membranes modified with additional graphene layer in order to enhance tritium separation factor was used. Both differences in the kinetics of the hydrogen evolution reaction and transport through the graphene layer of different isotopes are the driving factors expecting to affect the separation of hydrogen isotopes. The separation factor was measured both during the electrolysis and fuel cell stage by using different membranes. The facilitating effect of the graphene on the separation efficiency was determined during the study. Separation factor obtained by the proposed method was evidently higher than by other conventional methods.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"29 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384990","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 : 2024-01-03DOI: 10.1088/1741-4326/ad1a56
Adriano Stagni, N. Vianello, M. Agostini, C. Colandrea, S. Gorno, B. Labit, U. Sheikh, Luke Simons, Guang-Yu Sun, C. Tsui, M. Ugoletti, Yinghan Wang, C. Wüthrich, J. Boedo, Holger Reimerdes, C. Theiler
The impact of plasma shaping on the properties of high density H-mode scrape-off layer (SOL) profiles and transport at the outer midplane has been investigated on Tokamakà configuration variable. The experimental dataset has been acquired by evolving the upper triangularity while keeping the other parameters constant. The scan comprises δup values between 0.0 and 0.6, excluding negative triangularity scenarios. Within this study, a transition from type-I edge localised modes to the quasi-continuous exhaust regime takes place from low to high δup . The modification of the upstream SOL profiles has been assessed, in terms of separatrix quantities, within the αt turbulence control parameter theoretical framework (Eich et al 2020 Nucl. Fusion 60 056016). The target parallel heat load and the upstream near-SOL density profiles have been shown to broaden significantly for increasing αt . Correspondingly, in the far SOL a density shoulder formation is observed when moving from low to high δup . These behaviours have been correlated with an enhancement of the SOL fluctuation level, as registered by wall-mounted Langmuir probes as well as the thermal helium beam diagnostic. Specifically, both the background and the filamentary-induced fluctuating parts of the first wall ion saturation current signal are larger at higher δup , with filaments being ejected more frequently into the SOL. Comparison of two pulses at the extremes of the δup scan range, but with otherwise same input parameters, shows that the midplane neutral pressure does not change much during the H-mode phase of the discharge. This indicates that indirect effects of the change in geometry, linked to first wall recycling sources, should not play a significant role. The total core radiation increases at high δup , on account of a stronger plasma–wall interaction and resulting larger carbon impurity intake from the first wall. This is likely associated to the enhanced first wall fluctuations, as well as a smaller outer gap and the close-to-double-null magnetic topology at high shaping.
在托卡马克（Tokamakà）配置变量上研究了等离子体整形对高密度 H 模式刮除层（SOL）剖面特性和外中面传输的影响。实验数据集是在保持其他参数不变的情况下，通过改变上三角度获得的。扫描包括 0.0 至 0.6 之间的 δup 值，不包括负三角形情况。在这项研究中，从低δup 到高δup，发生了从 I 型边缘局部模式到准连续排气系统的过渡。在 αt 湍流控制参数理论框架内（Eich 等 2020 核聚变 60 056016），从分离矩阵量的角度评估了上游 SOL 曲线的变化。研究表明，随着 αt 的增大，目标平行热负荷和上游近 SOL 密度曲线会显著变宽。相应地，从低δup 到高δup 时，在远 SOL 中观察到密度肩的形成。这些行为与 SOL 波动水平的增强有关，壁装朗缪尔探针和热氦束诊断仪都记录了这一波动。具体来说，第一壁离子饱和电流信号的背景和丝状体引起的波动部分在更高δup 时都更大，丝状体更频繁地喷射到 SOL 中。在输入参数相同的情况下，对位于 δup 扫描范围两端的两个脉冲进行比较，结果表明在放电的 H 模式阶段，中性面压力变化不大。这表明，与第一壁循环源有关的几何形状变化的间接影响应该不会起很大作用。在高δup 时，由于等离子体与第一壁的相互作用更强，导致第一壁吸入的碳杂质更多，因此堆芯总辐射增加。这可能与第一壁波动的增强、较小的外隙以及高整形时接近双零的磁拓扑结构有关。
{"title":"The effect of plasma shaping on high density H-mode SOL profiles and fluctuations in TCV","authors":"Adriano Stagni, N. Vianello, M. Agostini, C. Colandrea, S. Gorno, B. Labit, U. Sheikh, Luke Simons, Guang-Yu Sun, C. Tsui, M. Ugoletti, Yinghan Wang, C. Wüthrich, J. Boedo, Holger Reimerdes, C. Theiler","doi":"10.1088/1741-4326/ad1a56","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1a56","url":null,"abstract":"The impact of plasma shaping on the properties of high density H-mode scrape-off layer (SOL) profiles and transport at the outer midplane has been investigated on Tokamakà configuration variable. The experimental dataset has been acquired by evolving the upper triangularity while keeping the other parameters constant. The scan comprises δup values between 0.0 and 0.6, excluding negative triangularity scenarios. Within this study, a transition from type-I edge localised modes to the quasi-continuous exhaust regime takes place from low to high δup . The modification of the upstream SOL profiles has been assessed, in terms of separatrix quantities, within the αt turbulence control parameter theoretical framework (Eich et al 2020 Nucl. Fusion 60 056016). The target parallel heat load and the upstream near-SOL density profiles have been shown to broaden significantly for increasing αt . Correspondingly, in the far SOL a density shoulder formation is observed when moving from low to high δup . These behaviours have been correlated with an enhancement of the SOL fluctuation level, as registered by wall-mounted Langmuir probes as well as the thermal helium beam diagnostic. Specifically, both the background and the filamentary-induced fluctuating parts of the first wall ion saturation current signal are larger at higher δup , with filaments being ejected more frequently into the SOL. Comparison of two pulses at the extremes of the δup scan range, but with otherwise same input parameters, shows that the midplane neutral pressure does not change much during the H-mode phase of the discharge. This indicates that indirect effects of the change in geometry, linked to first wall recycling sources, should not play a significant role. The total core radiation increases at high δup , on account of a stronger plasma–wall interaction and resulting larger carbon impurity intake from the first wall. This is likely associated to the enhanced first wall fluctuations, as well as a smaller outer gap and the close-to-double-null magnetic topology at high shaping.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"60 22","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451314","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 : 2024-01-03DOI: 10.1088/1741-4326/ad1a57
H. Järleblad, Luke Stagner, Jacob Eriksson, M. Nocente, K. Kirov, M. R. Larsen, Bo Simmendefeldt Schmidt, M. Maslov, Damian King, D. Keeling, C. Maggi, Jeronimo Garcia, E. Lerche, P. Mantica, Yiqiu Dong, M. Salewski
In the JET DTE2 deuterium-tritium campaign, neutron diagnostics were employed to measure 14 MeV neutrons originating from D(T,n)4He reactions. In discharge 99965, a diamond matrix detector (KM14) and a magnetic proton recoil (MPRu) detector with a vertical and an oblique line-of-sight were used, respectively. At the timepoints of interest, a significant decrease in the expected diagnostic signals can be observed as electromagnetic wave heating in the ion cyclotron range of frequencies (ICRF) is switched off. Utilizing only TRANSP simulation data, the fast-ion distribution is found to have been likely composed mostly of trapped orbits. In contrast, analysis performed using orbit weight functions revealed that the majority of neutrons in the KM14 Ed=9.3 MeV and MPRu Xcm=33 cm measurement bins are to have originated from fast deuterium ions on co-passing orbits. This work explains the perhaps surprising results and shows that the relative signal decrease as ICRF heating is switched off is largest for counter-passing orbits. Finally, for the magnetic equilibria of interest, it is shown how stagnation orbits, corresponding to ∼1 % of the fast-ion distribution, were completely unobservable by the KM14 diagnostic.
{"title":"Fast-ion orbit origin of neutron emission spectroscopy measurements in the JET DT campaign","authors":"H. Järleblad, Luke Stagner, Jacob Eriksson, M. Nocente, K. Kirov, M. R. Larsen, Bo Simmendefeldt Schmidt, M. Maslov, Damian King, D. Keeling, C. Maggi, Jeronimo Garcia, E. Lerche, P. Mantica, Yiqiu Dong, M. Salewski","doi":"10.1088/1741-4326/ad1a57","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1a57","url":null,"abstract":"In the JET DTE2 deuterium-tritium campaign, neutron diagnostics were employed to measure 14 MeV neutrons originating from D(T,n)4He reactions. In discharge 99965, a diamond matrix detector (KM14) and a magnetic proton recoil (MPRu) detector with a vertical and an oblique line-of-sight were used, respectively. At the timepoints of interest, a significant decrease in the expected diagnostic signals can be observed as electromagnetic wave heating in the ion cyclotron range of frequencies (ICRF) is switched off. Utilizing only TRANSP simulation data, the fast-ion distribution is found to have been likely composed mostly of trapped orbits. In contrast, analysis performed using orbit weight functions revealed that the majority of neutrons in the KM14 Ed=9.3 MeV and MPRu Xcm=33 cm measurement bins are to have originated from fast deuterium ions on co-passing orbits. This work explains the perhaps surprising results and shows that the relative signal decrease as ICRF heating is switched off is largest for counter-passing orbits. Finally, for the magnetic equilibria of interest, it is shown how stagnation orbits, corresponding to ∼1 % of the fast-ion distribution, were completely unobservable by the KM14 diagnostic.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"49 23","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451663","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 : 2024-01-03DOI: 10.1088/1741-4326/ad1a54
Sun Ho Kim, Jonggab Jo, J. Wang, Soobin Lim, Seongcheol Kim, Y. S. Hwang
An efficient central or off-axis current drive is necessary for the steady-state operation of tokamak fusion reactors. The fast wave branch in the frequency range above two times the lower hybrid resonance frequency at high density, the so-called LHFW, could be such an efficient current drive scheme in high density and high temperature of reactor-grade tokamak plasmas. This is because it has a higher parallel wave electric field for efficient Landau damping, compared to the fast wave branches in other frequency ranges, and it can more deeply penetrate high density plasmas than the slow wave in the same frequency range. An experimental study has been carried out to confirm the feasibility, in collaboration with KAERI, SNU, KWU, and KAPRA, in VEST. The results show that plasma current can be driven by the fast electrons generated by the LHFW. The details are reported including the theoretical background and RF system as well as the experiment results.
托卡马克核聚变反应堆的稳态运行需要高效的中心或离轴电流驱动。在反应堆级托卡马克等离子体的高密度和高温条件下，频率范围高于下混合共振频率两倍的快波分支，即所谓的 LHFW，可以成为一种高效的电流驱动方案。这是因为与其他频率范围的快波分支相比，它具有更高的平行波电场，可实现高效的朗道阻尼，而且与相同频率范围的慢波相比，它能更深入地穿透高密度等离子体。为了证实其可行性，我们与韩国航空航天研究所、韩国国家科学院、韩国水利大学和韩国航空航天研究所合作，在 VEST 开展了一项实验研究。结果表明，等离子体电流可以由低频慢波产生的快速电子驱动。报告的详细内容包括理论背景和射频系统以及实验结果。
{"title":"Current Drive by using Lower Hybrid Fast Wave in VEST","authors":"Sun Ho Kim, Jonggab Jo, J. Wang, Soobin Lim, Seongcheol Kim, Y. S. Hwang","doi":"10.1088/1741-4326/ad1a54","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1a54","url":null,"abstract":"\u0000 An efficient central or off-axis current drive is necessary for the steady-state operation of tokamak fusion reactors. The fast wave branch in the frequency range above two times the lower hybrid resonance frequency at high density, the so-called LHFW, could be such an efficient current drive scheme in high density and high temperature of reactor-grade tokamak plasmas. This is because it has a higher parallel wave electric field for efficient Landau damping, compared to the fast wave branches in other frequency ranges, and it can more deeply penetrate high density plasmas than the slow wave in the same frequency range. An experimental study has been carried out to confirm the feasibility, in collaboration with KAERI, SNU, KWU, and KAPRA, in VEST. The results show that plasma current can be driven by the fast electrons generated by the LHFW. The details are reported including the theoretical background and RF system as well as the experiment results.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"122 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139387852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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