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Optimization of nonlinear turbulence in stellarators 优化恒星器中的非线性湍流
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-04-11 DOI: 10.1017/s0022377824000369
P. Kim, S. Buller, R. Conlin, W. Dorland, D.W. Dudt, R. Gaur, R. Jorge, E. Kolemen, M. Landreman, N.R. Mandell, D. Panici
{"title":"Optimization of nonlinear turbulence in stellarators","authors":"P. Kim, S. Buller, R. Conlin, W. Dorland, D.W. Dudt, R. Gaur, R. Jorge, E. Kolemen, M. Landreman, N.R. Mandell, D. Panici","doi":"10.1017/s0022377824000369","DOIUrl":"https://doi.org/10.1017/s0022377824000369","url":null,"abstract":"We present new stellarator equilibria that have been optimized for reduced turbulent transport using nonlinear gyrokinetic simulations within the optimization loop. The optimization routine involves coupling the pseudo-spectral GPU-native gyrokinetic code <jats:monospace>GX</jats:monospace> with the stellarator equilibrium and optimization code <jats:monospace>DESC</jats:monospace>. Since using <jats:monospace>GX</jats:monospace> allows for fast nonlinear simulations, we directly optimize for reduced nonlinear heat fluxes. To handle the noisy heat flux traces returned by these simulations, we employ the simultaneous perturbation stochastic approximation (SPSA) method that only uses two objective function evaluations for a simple estimate of the gradient. We show several examples that optimize for both reduced heat fluxes and good quasi-symmetry as a proxy for low neoclassical transport. Finally, we run full transport simulations using the <jats:monospace>T3D</jats:monospace> stellarator transport code to evaluate the changes in the macroscopic profiles.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"47 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140602252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
Energetic particle tracing in optimized quasi-symmetric stellarator equilibria 优化准对称恒星器平衡中的能量粒子追踪
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-04-05 DOI: 10.1017/s0022377824000400
P.A. Figueiredo, R. Jorge, J. Ferreira, P. Rodrigues
{"title":"Energetic particle tracing in optimized quasi-symmetric stellarator equilibria","authors":"P.A. Figueiredo, R. Jorge, J. Ferreira, P. Rodrigues","doi":"10.1017/s0022377824000400","DOIUrl":"https://doi.org/10.1017/s0022377824000400","url":null,"abstract":"Recent developments in the design of magnetic confinement fusion devices have allowed the construction of exceptionally optimized stellarator configurations. The near-axis expansion in particular has been proven to enable the construction of magnetic configurations with good confinement properties while taking only a fraction of the usual computation time to generate optimized magnetic equilibria. However, not much is known about the overall features of fast-particle orbits computed in such analytical, yet simplified, equilibria when compared with those originating from accurate equilibrium solutions. This work aims to assess and demonstrate the potential of the near-axis expansion to provide accurate information on particle orbits and to compute loss fractions in moderate to high aspect ratios. The configurations used here are all scaled to fusion-relevant parameters and approximate quasi-symmetry to various degrees. This allows us to understand how deviations from quasi-symmetry affect particle orbits and what are their effects on the estimation of the loss fraction. Guiding-centre trajectories of fusion-born alpha particles are traced using gyronimo and SIMPLE codes under the NEAT framework, showing good numerical agreement. Discrepancies between near-axis and magnetohydrodynamic fields have minor effects on passing particles but significant effects on trapped particles, especially in quasi-helically symmetric magnetic fields. Effective expressions were found for estimating orbit widths and passing–trapped separatrix in quasi-symmetric near-axis fields. Loss fractions agree in the prompt losses regime but diverge afterwards.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"51 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140585063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
Asymptotic quasisymmetric high-beta three-dimensional magnetohydrodynamic equilibria near axisymmetry 接近轴对称的渐近准对称高贝塔三维磁流体动力学平衡态
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-04-05 DOI: 10.1017/s0022377824000357
Wrick Sengupta, Nikita Nikulsin, Rahul Gaur, Amitava Bhattacharjee
{"title":"Asymptotic quasisymmetric high-beta three-dimensional magnetohydrodynamic equilibria near axisymmetry","authors":"Wrick Sengupta, Nikita Nikulsin, Rahul Gaur, Amitava Bhattacharjee","doi":"10.1017/s0022377824000357","DOIUrl":"https://doi.org/10.1017/s0022377824000357","url":null,"abstract":"Quasisymmetry (QS), a hidden symmetry of the magnetic field strength, is known to support nested flux surfaces and provide superior particle confinement in stellarators. In this work, we study the ideal magnetohydrodynamic (MHD) equilibrium and stability of high-beta plasma in a large-aspect-ratio stellarator. In particular, we show that the lowest-order description of a near-axisymmetric equilibrium vastly simplifies the problem of three-dimensional quasisymmetric MHD equilibria, which can be reduced to a standard elliptic Grad–Shafranov equation for the flux function. We show that any large-aspect-ratio tokamak, deformed periodically in the vertical direction, is a stellarator with approximate volumetric QS. We discuss exact analytical solutions and numerical benchmarks. Finally, we discuss the ideal ballooning and interchange stability of some of our equilibrium configurations.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"51 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140584999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
Study of the pellet ablation cloud using the tomography technique for two-directional simultaneous photography in GAMMA 10/PDX 利用 GAMMA 10/PDX 双向同步摄影断层扫描技术研究颗粒消融云层
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-04-05 DOI: 10.1017/s0022377824000394
M. Yoshikawa, Y. Nakashima, J. Kohagura, Y. Shima, S. Kobayashi, R. Minami, N. Ezumi, M. Sakamoto
{"title":"Study of the pellet ablation cloud using the tomography technique for two-directional simultaneous photography in GAMMA 10/PDX","authors":"M. Yoshikawa, Y. Nakashima, J. Kohagura, Y. Shima, S. Kobayashi, R. Minami, N. Ezumi, M. Sakamoto","doi":"10.1017/s0022377824000394","DOIUrl":"https://doi.org/10.1017/s0022377824000394","url":null,"abstract":"The pellet ablation mechanism is an interesting subject for plasma fuelling in fusion plasmas. In GAMMA 10/PDX, pellet injection experiments for higher density plasma production are planned to conduct detached plasma experiments in the higher density plasma condition. We measured the pellet ablation cloud by using the two-directional simultaneous photography system in GAMMA 10/PDX. The tomography reconstruction technique was used for considering the pellet trajectory in the plasma and pellet ablation. The three-dimensional pellet trajectory and pellet ablation images in the plasma were clearly obtained for the first time, to the best of our knowledge.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"36 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140585266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
Effects of multi-dimensionality and energy exchange on electrostatic current-driven plasma instabilities and turbulence 多维性和能量交换对静电电流驱动等离子体不稳定性和湍流的影响
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-03-27 DOI: 10.1017/s0022377824000230
Wai Hong Ronald Chan, Kentaro Hara, Iain D. Boyd
{"title":"Effects of multi-dimensionality and energy exchange on electrostatic current-driven plasma instabilities and turbulence","authors":"Wai Hong Ronald Chan, Kentaro Hara, Iain D. Boyd","doi":"10.1017/s0022377824000230","DOIUrl":"https://doi.org/10.1017/s0022377824000230","url":null,"abstract":"Large-amplitude current-driven plasma instabilities, which can transition to the Buneman instability, were observed in one-dimensional simulations to generate high-energy back-streaming ions. We investigate the saturation of multi-dimensional plasma instabilities and its effects on energetic ion formation. Such ions directly impact spacecraft thruster lifetimes and are associated with magnetic reconnection and cosmic ray inception. An Eulerian Vlasov–Poisson solver employing the grid-based direct kinetic method is used to study the growth and saturation of 2D2V collisionless, electrostatic current-driven instabilities spanning two dimensions each in the configuration (D) and velocity (V) spaces supporting ion and electron phase-space transport. Four stages characterise the electric potential evolution in such instabilities: linear modal growth, harmonic growth, accelerated growth via quasi-linear mechanisms alongside nonlinear fill-in and saturated turbulence. Its transition and isotropisation process bears considerable similarities to the development of hydrodynamic turbulence. While a tendency to isotropy is observed in the plasma waves, followed by electron and then ion phase spaces after several ion-acoustic periods, the formation of energetic back-streaming ions is more limited in the 2D2V than in the 1D1V simulations. Plasma waves formed by two-dimensional electrostatic kinetic instabilities can propagate in the direction perpendicular to the net electron drift. Thus, large-amplitude multi-dimensional waves generate high-energy transverse-streaming ions and eventually limit energetic backward-streaming ions along the longitudinal direction. The multi-dimensional study sheds light on interactions between longitudinal and transverse electrostatic plasma instabilities, as well as fundamental characteristics of the inception and sustenance of unmagnetised plasma turbulence.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"28 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140315041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
Transient versus steady-state solutions: a qualitative study 瞬态与稳态解决方案：定性研究
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-03-27 DOI: 10.1017/s0022377824000187
D. Van Eester, E.A. Lerche, E. Pawelec, E. Solano
{"title":"Transient versus steady-state solutions: a qualitative study","authors":"D. Van Eester, E.A. Lerche, E. Pawelec, E. Solano","doi":"10.1017/s0022377824000187","DOIUrl":"https://doi.org/10.1017/s0022377824000187","url":null,"abstract":"In view of the ultimate goal of producing long-lasting quasi-stationary discharges required for future fusion power stations, the numerical study of steady-state solutions of equations describing the particle and energy balance rightfully gets ample attention. Transient states may, however, differ significantly from the steady state ultimately reached and will – in practice – impact on the actual fate of the discharge. Using brutally simple models, the present paper highlights a number of aspects to illustrate this dynamics. It e.g. shows the different signature of wave and beam heating, potentially giving room to transiently trigger desirable effects that may allow us to better steer a discharge.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"5 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140315045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
The gyrokinetic dispersion relation of microtearing modes in collisionless toroidal plasmas 无碰撞环形等离子体中微撕裂模式的陀螺动散布关系
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-03-21 DOI: 10.1017/s0022377824000175
B.D.G. Chandran, A.A. Schekochihin
{"title":"The gyrokinetic dispersion relation of microtearing modes in collisionless toroidal plasmas","authors":"B.D.G. Chandran, A.A. Schekochihin","doi":"10.1017/s0022377824000175","DOIUrl":"https://doi.org/10.1017/s0022377824000175","url":null,"abstract":"We solve the linearized gyrokinetic equation, quasineutrality condition and Ampere's law to obtain the dispersion relation of microtearing modes (MTMs) in collisionless low-<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0022377824000175_inline1.png\" /> <jats:tex-math>$beta$</jats:tex-math> </jats:alternatives> </jats:inline-formula> toroidal plasmas. Consistent with past studies, we find that MTMs are driven unstable by the electron temperature gradient and that this instability drive is mediated by magnetic drifts. The dispersion relation that we derive can be evaluated numerically very quickly and may prove useful for devising strategies to mitigate MTM instability in fusion devices.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"31 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140203740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
The residual flow in well-optimized stellarators 优化恒星器中的剩余流量
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-03-21 DOI: 10.1017/s002237782400031x
G.G. Plunk, P. Helander
{"title":"The residual flow in well-optimized stellarators","authors":"G.G. Plunk, P. Helander","doi":"10.1017/s002237782400031x","DOIUrl":"https://doi.org/10.1017/s002237782400031x","url":null,"abstract":"The gyrokinetic theory of the residual flow, in the electrostatic limit, is revisited, with optimized stellarators in mind. We consider general initial conditions for the problem, and identify cases that lead to a non-zonal residual electrostatic potential, i.e. one having a significant component that varies within a flux surface. We investigate the behaviour of the ‘intermediate residual’ in stellarators, a measure of the flow that remains after geodesic acoustic modes have damped away, but before the action of the slower damping that is caused by unconfined particle orbits. The case of a quasi-isodynamic stellarator is identified as having a particularly large such residual, owing to the small orbit width achieved by optimization.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"8 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140203798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
Charged particle collisionless transport near the X-point of the two-wire model 双线模型 X 点附近的带电粒子无碰撞输运
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-03-19 DOI: 10.1017/s0022377824000321
Bin Ahn, Yegeon Lim, Hoiyun Jeong, Hae June Lee, Gyung Jin Choi, Y.-C. Ghim
{"title":"Charged particle collisionless transport near the X-point of the two-wire model","authors":"Bin Ahn, Yegeon Lim, Hoiyun Jeong, Hae June Lee, Gyung Jin Choi, Y.-C. Ghim","doi":"10.1017/s0022377824000321","DOIUrl":"https://doi.org/10.1017/s0022377824000321","url":null,"abstract":"Collisionless charged particle motion and its transport in the two-wire model (TWM) with no axial magnetic fields is investigated numerically. The TWM configuration contains a magnetic X-point, and single particle motions in such a field have two conserved quantities: the total kinetic energy and the base field line value which is a quantity derived from the axial canonical momentum. As gyrating particles travel along the field lines, they may reach near the X-point region where the magnetic moment, the first adiabatic invariant, can be occasionally shifted due to a large gradient of the field. When the magnetic moment becomes large, resulting in a large Larmor radius, particles probabilistically cross the X-point to migrate to the opposite side of the TWM configuration. These phenomena are investigated with single particle simulations. We find that the statistical behaviour of the seemingly chaotic magnetic moment shifts are completely determined by the two aforementioned conserved quantities, and also that there exists a threshold energy, determined by the base field line value, allowing only particles with a higher energy to cross the separatrix and migrate. It is found that the crossing time is distributed exponentially, and that the migration confinement time, which is the average crossing time, is shorter for particles with a base field line closer to the separatrix and a higher energy. We provide an empirical expression, derived with the simulations, for estimating the collisionless migration confinement time.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"80 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140167871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
Loss-cone stabilization in rotating mirrors: thresholds and thermodynamics 旋转镜中的损耗锥稳定：阈值和热力学
IF 2.5 3区 物理与天体物理
Journal of Plasma Physics Pub Date : 2024-03-15 DOI: 10.1017/s0022377824000205
E.J. Kolmes, I.E. Ochs, N.J. Fisch
{"title":"Loss-cone stabilization in rotating mirrors: thresholds and thermodynamics","authors":"E.J. Kolmes, I.E. Ochs, N.J. Fisch","doi":"10.1017/s0022377824000205","DOIUrl":"https://doi.org/10.1017/s0022377824000205","url":null,"abstract":"In the limit of sufficiently fast rotation, rotating mirror traps are known to be stable against the loss-cone modes associated with conventional (non-rotating) mirrors. This paper calculates how quickly a mirror configuration must rotate in order for several of these modes to be stabilized (in particular, the high-frequency convective loss cone, drift cyclotron loss cone and Dory–Guest–Harris modes). Commonalities in the stabilization conditions for these modes then motivate a modified formulation of the Gardner free energy and diffusively accessible free energy to be used for systems in which the important modes have wavevectors that are orthogonal or nearly orthogonal to the magnetic field, as well as a modification to include the effects of a loss region in phase space.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"20 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140156743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
引用次数: 0
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