Pub Date : 2024-09-04DOI: 10.1088/1741-4326/ad703b
A.S. Moore, L. Divol, B. Bachmann, R. Bionta, D. Bradley, D.T. Casey, P. Celliers, H. Chen, A. Do, E. Dewald, M. Eckart, D. Fittinghoff, J. Frenje, M. Gatu-Johnson, H. Geppert-Kleinrath, V. Geppert-Kleinrath, G. Grim, K. Hahn, M. Hohenberger, J. Holder, O. Hurricane, N. Izumi, S. Kerr, S.F. Khan, J.D. Kilkenny, Y. Kim, B. Kozioziemski, N. Lemos, A.G. MacPhee, P. Michel, M. Millot, K.D. Meaney, S. Nagel, A. Pak, J.E. Ralph, J.S. Ross, M.S. Rubery, D.J. Schlossberg, V. Smalyuk, G. Swadling, R. Tommasini, C. Trosseille, A.B. Zylstra, A. Mackinnon, J.D. Moody, O.L. Landen, R. Town
Fusion ignition by inertial confinement requires compression and heating of the fusion fuel to temperatures in excess of 5 keV and densities exceeding hundreds of g/cc. In August 2021, this scientific milestone was surpassed at the National Ignition Facility (NIF), when the Lawson criterion for ignition was exceeded generating 1.37MJ of fusion energy (Abu-Shawareb et al 2022 Phys. Rev. Lett.129 075001), and then in December 2022 target gain >1 was realized with the production of 3.1MJ of fusion energy from a target driven by 2.0MJ of laser energy (Abu-Shawareb et al 2024 Phys. Rev. Lett.132 065102). At the NIF, inertial confinement fusion research primarily uses a laser indirect drive in which the fusion capsule is surrounded by a high-Z enclosure (‘hohlraum’) used to convert the directed laser energy into a symmetric x-ray drive on the capsule. Precise measurements of the plasma conditions, x-rays, γ-rays and neutrons produced are key to understanding the pathway to higher performance. This paper discusses the diagnostics and measurement techniques developed to understand these experiments, focusing on three main topics: (1) key diagnostic developments for achieving igniting plasmas, (2) novel signatures related to thermonuclear burn and (3) advances to diagnostic capabilities in the igniting regime with a perspective toward developments for intertial fusion energy.
{"title":"Diagnosing inertial confinement fusion ignition","authors":"A.S. Moore, L. Divol, B. Bachmann, R. Bionta, D. Bradley, D.T. Casey, P. Celliers, H. Chen, A. Do, E. Dewald, M. Eckart, D. Fittinghoff, J. Frenje, M. Gatu-Johnson, H. Geppert-Kleinrath, V. Geppert-Kleinrath, G. Grim, K. Hahn, M. Hohenberger, J. Holder, O. Hurricane, N. Izumi, S. Kerr, S.F. Khan, J.D. Kilkenny, Y. Kim, B. Kozioziemski, N. Lemos, A.G. MacPhee, P. Michel, M. Millot, K.D. Meaney, S. Nagel, A. Pak, J.E. Ralph, J.S. Ross, M.S. Rubery, D.J. Schlossberg, V. Smalyuk, G. Swadling, R. Tommasini, C. Trosseille, A.B. Zylstra, A. Mackinnon, J.D. Moody, O.L. Landen, R. Town","doi":"10.1088/1741-4326/ad703b","DOIUrl":"https://doi.org/10.1088/1741-4326/ad703b","url":null,"abstract":"Fusion ignition by inertial confinement requires compression and heating of the fusion fuel to temperatures in excess of 5 keV and densities exceeding hundreds of g/cc. In August 2021, this scientific milestone was surpassed at the National Ignition Facility (NIF), when the Lawson criterion for ignition was exceeded generating 1.37MJ of fusion energy (Abu-Shawareb <italic toggle=\"yes\">et al</italic> 2022 <italic toggle=\"yes\">Phys. Rev. Lett.</italic> <bold>129</bold> 075001), and then in December 2022 target gain >1 was realized with the production of 3.1MJ of fusion energy from a target driven by 2.0MJ of laser energy (Abu-Shawareb <italic toggle=\"yes\">et al</italic> 2024 <italic toggle=\"yes\">Phys. Rev. Lett.</italic> <bold>132</bold> 065102). At the NIF, inertial confinement fusion research primarily uses a laser indirect drive in which the fusion capsule is surrounded by a high-Z enclosure (‘hohlraum’) used to convert the directed laser energy into a symmetric x-ray drive on the capsule. Precise measurements of the plasma conditions, x-rays, <italic toggle=\"yes\">γ</italic>-rays and neutrons produced are key to understanding the pathway to higher performance. This paper discusses the diagnostics and measurement techniques developed to understand these experiments, focusing on three main topics: (1) key diagnostic developments for achieving igniting plasmas, (2) novel signatures related to thermonuclear burn and (3) advances to diagnostic capabilities in the igniting regime with a perspective toward developments for intertial fusion energy.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"20 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142212114","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 : 2024-09-03DOI: 10.1088/1741-4326/ad6ce7
M. Peterka, J. Seidl, T. Markovic, A. Loarte, N.C. Logan, J.-K. Park, P. Cahyna, J. Havlicek, M. Imrisek, L. Kripner, R. Panek, M. Sos, P. Bilkova, K. Bogar, P. Bohm, A. Casolari, Y. Gribov, O. Grover, P. Hacek, M. Hron, K. Kovarik, M. Tomes, D. Tskhakaya, J. Varju, P. Vondracek, V. Weinzettl, the COMPASS Teama
This work presents the first analysis of the disruptive locked mode (LM) triggered by the dynamics of a confinement change. It shows that, under certain conditions, the LM threshold during the transient is significantly lower than expected from steady states. We investigate the sensitivity to a controlled n = 1 error field (EF) activated prior to the L-H transition in the COMPASS tokamak, at q95 ∼ 3, βN ∼ 1, and using EF coils on the high-field side of the vessel. A threshold for EF penetration subsequent to the L-H transition is identified, which shows no significant trend with density or applied torque, and is an apparent consequence of the reduced intrinsic rotation of the 2/1 mode during this transient phase. This finding challenges the assumption made in theoretical and empirical works that natural mode rotation can be predicted by global plasma parameters and urges against using any parametric EF penetration scaling derived from steady-state experiments to define the EF correction strategy in the entire discharge. Furthermore, even at EFs below the identified penetration threshold, disruptive locking of sawtooth-seeded 2/1 tearing modes is observed after about 30% of L-H transitions without external torque.
这项研究首次分析了由约束变化动态引发的破坏性锁定模式(LM)。它表明,在某些条件下,瞬态期间的锁定模式阈值明显低于稳定状态下的预期阈值。我们研究了在 COMPASS 托卡马克的 L-H 转换之前,在 q95 ∼ 3,βN ∼ 1 的条件下,使用容器高场侧的 EF 线圈激活的受控 n = 1 误差场(EF)的敏感性。确定了 L-H 转换后 EF 穿透的阈值,该阈值与密度或应用扭矩无明显趋势,是 2/1 模式在此瞬态阶段本征旋转减少的明显结果。这一发现挑战了理论和经验研究中的假设,即自然模式旋转可由全局等离子体参数预测,并敦促不要使用从稳态实验中得出的任何参数 EF 穿透比例来定义整个放电过程中的 EF 校正策略。此外,即使在低于所确定的穿透阈值的 EF 下,在没有外部扭矩的情况下,在约 30% 的 L-H 转变之后,也能观察到锯齿种子 2/1 撕裂模式的破坏性锁定。
{"title":"Quantification of locked mode instability triggered by a change in confinement","authors":"M. Peterka, J. Seidl, T. Markovic, A. Loarte, N.C. Logan, J.-K. Park, P. Cahyna, J. Havlicek, M. Imrisek, L. Kripner, R. Panek, M. Sos, P. Bilkova, K. Bogar, P. Bohm, A. Casolari, Y. Gribov, O. Grover, P. Hacek, M. Hron, K. Kovarik, M. Tomes, D. Tskhakaya, J. Varju, P. Vondracek, V. Weinzettl, the COMPASS Teama","doi":"10.1088/1741-4326/ad6ce7","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6ce7","url":null,"abstract":"This work presents the first analysis of the disruptive locked mode (LM) triggered by the dynamics of a confinement change. It shows that, under certain conditions, the LM threshold during the transient is significantly lower than expected from steady states. We investigate the sensitivity to a controlled <italic toggle=\"yes\">n</italic> = 1 error field (EF) activated prior to the L-H transition in the COMPASS tokamak, at <italic toggle=\"yes\">q</italic><sub>95</sub> ∼ 3, <italic toggle=\"yes\">β</italic><sub>N</sub> ∼ 1, and using EF coils on the high-field side of the vessel. A threshold for EF penetration subsequent to the L-H transition is identified, which shows no significant trend with density or applied torque, and is an apparent consequence of the reduced intrinsic rotation of the 2/1 mode during this transient phase. This finding challenges the assumption made in theoretical and empirical works that natural mode rotation can be predicted by global plasma parameters and urges against using any parametric EF penetration scaling derived from steady-state experiments to define the EF correction strategy in the entire discharge. Furthermore, even at EFs below the identified penetration threshold, disruptive locking of sawtooth-seeded 2/1 tearing modes is observed after about 30% of L-H transitions without external torque.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"76 2 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142212116","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 : 2024-09-03DOI: 10.1088/1741-4326/ad6ba5
G. Staebler, C. Bourdelle, J. Citrin, R. Waltz
The theory, development, and validation of reduced quasilinear models of gyrokinetic turbulent transport in the closed flux surface core of tokamaks is reviewed. In combination with neoclassical collisional transport, these models are successful in accurately predicting core tokamak plasma temperature, density, rotation, and impurity profiles in a variety of confinement regimes. Refined experimental tests have been performed to validate the predictions of the quasilinear models, probing changes in the dominant gyrokinetic instabilities, as reflected in fluctuation measurements, cross-phases, and transport properties. These tests continue to produce a deeper understanding of the complex mix of instabilities at both electron and ion gyroradius scales.
{"title":"Quasilinear theory and modelling of gyrokinetic turbulent transport in tokamaks","authors":"G. Staebler, C. Bourdelle, J. Citrin, R. Waltz","doi":"10.1088/1741-4326/ad6ba5","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6ba5","url":null,"abstract":"The theory, development, and validation of reduced quasilinear models of gyrokinetic turbulent transport in the closed flux surface core of tokamaks is reviewed. In combination with neoclassical collisional transport, these models are successful in accurately predicting core tokamak plasma temperature, density, rotation, and impurity profiles in a variety of confinement regimes. Refined experimental tests have been performed to validate the predictions of the quasilinear models, probing changes in the dominant gyrokinetic instabilities, as reflected in fluctuation measurements, cross-phases, and transport properties. These tests continue to produce a deeper understanding of the complex mix of instabilities at both electron and ion gyroradius scales.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"24 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142212115","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 : 2024-09-03DOI: 10.1088/1741-4326/ad7272
H.R. Strauss, B.E. Chapman, B.C. Lyons
This paper deals with resistive wall tearing mode (RWTM) disruptions. RWTMs are closely related to resistive wall modes. RWTMs are tearing modes whose linear and nonlinear behavior is strongly dependent on the resistive wall outside the plasma. The consequence for ITER, is that the thermal quench timescale could be much longer than previously conjectured. Active feedback stabilization is another possible way to mitigate or prevent RWTM disruptions. Simulations of RWTM disruptions are reviewed for DIII-D and MST. MST has a longer resistive wall time than ITER, and disruptions are not observed experimentally when MST is operated as a standard tokamak. Simulations indicate that the RWTM disruption time scale is longer than the experimental shot time. Edge cooling causes contraction of the current profile, which can destabilize RWTMs. The equilibria studied here have the q = 2 rational surface close to the edge of the plasma, and low current density between the q = 2 surface and the wall. A sequence of low edge current model equilibria has major disruptions only for a resistive, not ideal, wall, and edge