Journal of Plasma Physics最新文献

英文中文

Generalized cross-helicity in non-ideal magnetohydrodynamics 非理想磁流体力学中的广义交叉螺旋度

IF 2.5 3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-12-01 DOI: 10.1017/s002237782300123x

Prachi Sharma, Asher Yahalom

The objective of the present paper is to investigate the constancy of the topological invariant, denoted the non-barotropic generalized cross-helicity in the case of non-ideal magnetohydrodynamics (MHD). Existing work considers only ideal barotropic MHD and ideal non-barotropic MHD. Here, we consider dissipative processes in the form of thermal conduction, finite electrical conductivity and viscosity and the effect of these processes on the cross-helicity conservation. An analytical approach has been adopted to obtain the mathematical expressions for the time derivative of the cross-helicity. Obtained results show that the generalized cross-helicity is not conserved in the non-ideal MHD limit and indicate which processes affect the helicity and which do not. Furthermore, we indicate the configurations in which this topological constant is conserved despite the dissipative processes. Some examples and applications are also given.

本文的目的是研究非理想磁流体力学(MHD)情况下拓扑不变量的恒常性，即非正压广义交叉螺旋度。现有工作只考虑理想正压MHD和理想非正压MHD。在这里，我们考虑了热传导、有限电导率和粘度形式的耗散过程，以及这些过程对交叉螺旋守恒的影响。采用解析的方法得到了交叉螺旋度时间导数的数学表达式。所得结果表明，广义交叉螺旋度在非理想MHD极限下是不守恒的，并指出了哪些过程影响螺旋度，哪些不影响。此外，我们指出了在耗散过程中该拓扑常数守恒的构型。并给出了一些实例和应用。

引用次数: 0

Guiding-centre orbit-following simulations of charge exchange loss of NBI ions with the finite Larmor radius effect 有限Larmor半径效应下NBI离子电荷交换损失的导向中心轨道跟踪模拟

IF 2.5 3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-11-29 DOI: 10.1017/s0022377823001186

Yingfeng Xu, Fuqiong Wang, Yongliang Li, Fangchuan Zhong

Guiding-centre orbit-following simulations of the charge exchange (CX) loss of neutral beam injection (NBI) ions are presented. The finite Larmor radius (FLR) effect in the fast ion–neutral collision can be included in guiding-centre orbit-following simulations by using the gyroaverage method. It is proved that the neutralization probability of fast ions computed by using the gyroaverage method in the guiding-centre orbit simulation is roughly the same as that computed in the full-orbit simulation when the time step in the guiding-centre simulation is the order of the gyroperiod. The CX losses of NBI fast ions for two NBIs in the EAST tokamak have been simulated by the guiding-centre orbit-following code GYCAVA, and the FLR effect in the fast ion–neutral collision on CX losses has been numerically studied. The CX effect of the fast ion–neutral collision can significantly enhance NBI ion losses on EAST. The FLR effect in the fast ion–neutral collision can enhance the CX loss. Vertical asymmetry of localized heat loads induced by CX losses is found, which is related to the FLR effect of fast ions and the strong radial gradient of the neutral density near the plasma edge. Heat loads induced by CX losses are localized in the regions near the poloidal angle

$theta =-60^circ$

, because the likelihood of exchanging charge is the largest at gyrophase

$xi ={rm pi}$

, and this leads to fast downwards moving neutrals. Fast ion loss fractions induced by CX increase with the neutral density increasing.

给出了中性束注入离子电荷交换损失的导向中心轨道跟踪模拟。利用陀螺平均方法，可以将快速离子中性碰撞中的有限拉莫尔半径(FLR)效应纳入导向中心轨道跟踪模拟中。证明了当制导中心模拟的时间步长为陀螺周期的阶数时，用陀螺平均法计算的快离子中和概率与全轨道模拟计算的中和概率大致相同。利用GYCAVA导向中心随轨程序模拟了EAST托卡马克中两个NBI快离子的CX损耗，并对快离子中性碰撞中FLR对CX损耗的影响进行了数值研究。快速离子中性碰撞的CX效应显著增加了NBI离子在EAST上的损失。快速离子中性碰撞中的FLR效应会增加CX的损耗。发现CX损耗引起的局部热负荷垂直不对称，这与快离子的FLR效应和等离子体边缘附近中性密度的强径向梯度有关。CX损失引起的热负荷集中在极向角$theta =-60^circ$附近的区域，因为在陀螺相$xi ={rm pi}$交换电荷的可能性最大，这导致了快速向下移动的中性离子。CX诱导的快速离子损失分数随着中性密度的增加而增加。

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引用次数: 0

Generation of energetic electrons by an electron cyclotron wave through stochastic heating in a spherical tokamak 球形托卡马克中电子回旋波通过随机加热产生高能电子

IF 2.5 3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-11-28 DOI: 10.1017/s0022377823001216

Mingyuan Wang, Shikui Cheng, Bing Liu, Shaodong Song, Dong Guo, Yunyang Song, Wenjun Liu, Debabrata Banerjee, Songjian Li, Tiantian Sun, Xiang Gu, Yingying Li, Jiaqi Dong, Yuejiang Shi, Y.-K. Martin Peng, Adi Liu

This study presents novel findings on stochastic electron heating via a random electron cyclotron wave (ECW) in a spherical tokamak. Hard x ray measurements demonstrate the time evolution of hard x ray counts at different energy bands, consistent with predictions from the stochastic heating model. The ECW heating rate shows a positive correlation with applied power, confirming the effectiveness of stochastic heating. Remarkably, the ECW-driven plasma current remains insensitive to ECW incidence angle, consistent with model predictions. The observed stochastic heating of electrons offers potential for exploring innovative non-inductive current drive modes in spherical tokamaks. This research contributes to the understanding of plasma behaviour and motivates the development of new models for non-inductive current drive in fusion devices.

本文提出了在球形托卡马克中利用随机电子回旋波(ECW)加热随机电子的新发现。硬x射线测量证明了硬x射线计数在不同能带上的时间演变，与随机加热模型的预测一致。ECW加热速率与外加功率呈正相关，证实了随机加热的有效性。值得注意的是，ECW驱动的等离子体电流对ECW入射角不敏感，这与模型预测一致。观察到的电子的随机加热为探索球形托卡马克中创新的无感电流驱动模式提供了潜力。这项研究有助于理解等离子体的行为，并推动了核聚变装置中无感电流驱动新模型的发展。

引用次数: 0

Nonlinear interaction of Alfvénic instabilities and turbulence via the modification of the equilibrium profiles 通过平衡剖面的修改，研究了气动系统的不稳定性与湍流的非线性相互作用

IF 2.5 3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-11-21 DOI: 10.1017/s0022377823001137

A. Biancalani, A. Bottino, D. Del Sarto, M.V. Falessi, T. Hayward-Schneider, P. Lauber, A. Mishchenko, B. Rettino, J.N. Sama, F. Vannini, L. Villard, X. Wang, F. Zonca, the ASDEX Upgrade team

Nonlinear simulations of Alfvén modes (AMs) driven by energetic particles (EPs) in the presence of turbulence are performed with the gyrokinetic particle-in-cell code ORB5. The AMs carry a heat flux, and consequently they nonlinearly modify the plasma temperature profiles. The isolated effect of this modification on the dynamics of turbulence is studied by means of electrostatic simulations. We find that turbulence is reduced when the profiles relaxed by the AM are used, with respect to the simulation where the unperturbed profiles are used. This is an example of indirect interaction of EPs and turbulence. First, an analytic magnetic equilibrium with circular concentric flux surfaces is considered as a simplified example for this study. Then, an application to an experimentally relevant case of ASDEX Upgrade is discussed.

利用胞内粒子的回旋动力学代码ORB5，对湍流条件下高能粒子驱动的alfv模态(AMs)进行了非线性模拟。AMs携带热流，因此它们非线性地改变了等离子体的温度分布。通过静电模拟研究了这种修正对湍流动力学的孤立影响。我们发现，相对于使用无扰动轮廓的模拟，当使用AM放松的轮廓时，湍流减少了。这是EPs与湍流间接相互作用的一个例子。首先，考虑了一个具有圆形同心磁面的解析磁平衡作为本研究的简化例子。然后，讨论了ASDEX升级在一个实验相关案例中的应用。

引用次数: 0

Using rational surfaces to improve pellet fuelling in stellarators 使用合理的表面来改善仿星器中的颗粒燃料

IF 2.5 3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-11-16 DOI: 10.1017/s0022377823001010

N. Panadero, K. J. McCarthy, B. Pégourié, R. Carrasco, I. García-Cortés, R. García, J. Hernández-Sánchez, F. Köchl, J. Martínez-Fernández, R. Sakamoto, the TJ-II team

Pellet injection is currently the primary candidate for achieving efficient plasma fuelling, one of the key issues for steady-state operation in large fusion devices. In this paper, pellet injection experiments are performed for several magnetic configurations of the TJ-II stellarator. The aim of this study is to increase the understanding of the role played by rational surfaces in plasmoid drift and deposition profiles in stellarators. The analysis of experimentally observed plasmoid drifts is supported by simulations of such cases made with the HPI2 code. Plasmoid drift is found to be significantly reduced, as in tokamaks, in the vicinity of rational surfaces. This is attributed to the fact that plasmoid external charge reconnection lengths are shorter near rational surfaces, resulting in a more effective damping of the plasmoid drift. Although the effect of plasmoid external currents on the drift is expected to be negligible in stellarators, compared with those caused by plasmoid internal currents, the effect observed in TJ-II is clearly measurable. In addition, simulations show that enhanced drift reductions near rational surfaces lead to significantly different deposition profiles for the magnetic configurations included in this study. This implies that it should be possible to select the magnetic configurations to obtain more efficient pellet fuelling.

颗粒注入是目前实现高效等离子体燃料的主要候选方法，这是大型聚变装置稳态运行的关键问题之一。本文对TJ-II仿星器的几种磁性结构进行了球团注入实验。本研究的目的是增加对合理表面在仿星器等离子体漂移和沉积剖面中所起作用的理解。实验观察到的等离子体漂移的分析得到了用HPI2代码模拟这种情况的支持。等离子体漂移被发现显著减少，如在托卡马克中，在有理表面附近。这是由于等离子体外电荷重联长度在有理表面附近较短，从而更有效地抑制了等离子体漂移。虽然在仿星器中，与等离子体内部电流引起的漂移相比，等离子体外部电流对漂移的影响可以忽略不计，但在TJ-II中观察到的影响显然是可以测量的。此外，模拟表明，在合理表面附近，漂移减小的增强导致本研究中包含的磁性配置的沉积剖面显著不同。这意味着，应该有可能选择磁性配置，以获得更有效的颗粒燃料。

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引用次数: 0

Resonant excitation of single Kelvin–Helmholtz high-order waves in a magnetized electron fluid vortex 磁化电子流体涡旋中单开尔文-亥姆霍兹高阶波的共振激发

3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-11-13 DOI: 10.1017/s0022377823001150

G. Maero, N. Panzeri, L. Patricelli, M. Romé

Thanks to the isomorphism between the drift-Poisson and Euler equations, inviscid two-dimensional fluid experiments can be performed in magnetized, single-component plasmas in Penning–Malmberg traps. Within this analogy, a trapped electron plasma column is equivalent to a two-dimensional vortex. Here, we focus our attention on the generation of V-states, i.e. $l$ -fold symmetric rotating vorticity patches where the deformation with respect to the circular cross-section has reached the nonlinear regime. We detail a linear theoretical analysis and devise an experimental routine to generate V-states through the precise excitation of single Kelvin–Helmholtz perturbations in a magnetized electron plasma. This technique makes use of suitable multipolar rotating electric fields, which are shown to be able to select the desired wavemode. In particular, with rotating fields, a hardware limitation in the highest accessible mode is removed and nonlinear Kelvin–Helmholtz waves of generic order $l$ can be attained, which pave the way for further investigations on the evolution and stability properties of V-states. Systematic experimental results for the selective mode growth in the linear and nonlinear regimes up to saturation and collapse are discussed.

由于漂泊松方程和欧拉方程之间的同构性，可以在Penning-Malmberg陷阱中磁化的单组分等离子体中进行无粘二维流体实验。在这个类比中，一个被捕获的电子等离子体柱相当于一个二维涡旋。在这里，我们将注意力集中在v态的产生上，即$l$ -fold对称旋转涡量斑块，其中相对于圆形截面的变形已经达到非线性状态。我们详细介绍了线性理论分析，并设计了一个实验程序，通过在磁化电子等离子体中精确激发单开尔文-亥姆霍兹微扰来产生v态。该技术利用合适的多极旋转电场，可以选择所需的波模。特别是在旋转场中，消除了最高可达模式的硬件限制，可以获得一般阶$l$的非线性开尔文-亥姆霍兹波，这为进一步研究v态的演化和稳定性特性铺平了道路。讨论了在线性和非线性状态下直至饱和和崩溃的选择模式生长的系统实验结果。

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引用次数: 0

On the analytical description of the nonlinear stage of the Weibel instability in collisionless anisotropic plasma 无碰撞各向异性等离子体中维贝尔不稳定性非线性阶段的解析描述

3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-11-08 DOI: 10.1017/s0022377823001198

A.A. Nechaev, A.A. Kuznetsov, Vl.V. Kocharovsky

On the basis of the energy invariants for the Weibel instability in a collisionless non-relativistic plasma, an analytical relation is obtained between the instantaneous values of the space-averaged energy density of the magnetic field, its dominant wavenumber and the average plasma anisotropy parameter. The relation is valid for arbitrary particle velocity distribution functions, including ones that vary with time at the nonlinear stage of instability. It is obtained under the assumption that the plasma is homogeneous along a certain axis, determined, for example, by an external magnetic field, and taking into account only the modes with wavevectors orthogonal to this axis. We give an estimate of the maximum magnetic field energy achievable during the Weibel instability and show that its ratio to the initial longitudinal energy of particles, even for a large initial plasma anisotropy parameter, cannot exceed the value approximately equal to 0.2. The obtained analytical relation is verified using two-dimensional particle-in-cell simulations.

在无碰撞非相对论等离子体Weibel不稳定性能量不变量的基础上，得到了磁场空间平均能量密度瞬时值、主导波数与平均等离子体各向异性参数之间的解析关系。该关系适用于任意粒子速度分布函数，包括非线性不稳定阶段随时间变化的粒子速度分布函数。它是在假设等离子体沿某一轴是均匀的情况下得到的，例如，由外部磁场决定，并且只考虑与该轴正交的波向量的模式。我们给出了在Weibel不稳定性期间所能达到的最大磁场能量的估计，并表明即使初始等离子体各向异性参数很大，其与粒子初始纵向能量的比值也不能超过约等于0.2的值。通过二维细胞内粒子模拟验证了所得到的解析关系。

引用次数: 0

The available energy of trapped electrons: a nonlinear measure for turbulent transport 捕获电子的可用能量:湍流输运的非线性测量

3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-10-01 DOI: 10.1017/s0022377823001083

R.J.J. Mackenbach, J.H.E. Proll, R. Wakelkamp, P. Helander

A collisionless plasma possesses a certain amount of ‘available energy’, which is that part of the thermal energy that can be converted into kinetic energy of plasma motion and electromagnetic fluctuations. In this paper we present a calculation of the available energy carried by trapped electrons in a slender non-omnigenous flux tube of plasma. This quantity is compared with gyrokinetic simulations of the nonlinear saturated radial energy flux resulting from turbulence driven by collisionless trapped-electron modes in various stellarators and a tokamak. The numerical calculation of available energy is fast and shows a strong correlation with the turbulent energy fluxes found in the gyrokinetic simulations. Indeed, the energy flux is found to be proportional to the available energy to the power of approximately $3/2$ , which is what one would expect from a simple argument. We furthermore investigate how available energy is distributed across different bounce wells, and it is found that deeply trapped electrons typically contribute most to the available energy. Finally, we investigate the dependence of available energy on gradient strength, and we find important differences between weakly and strongly driven regimes for stellarators and tokamaks.

一个无碰撞的等离子体拥有一定量的“可用能量”，这部分热能可以转化为等离子体运动和电磁波动的动能。本文给出了在细长非均匀等离子体通量管中捕获电子所携带的可用能量的计算方法。这一数值与在不同的仿星器和托卡马克中由无碰撞捕获电子模式驱动的非线性饱和径向能量流的陀螺动力学模拟结果进行了比较。有效能量的数值计算速度很快，并且与陀螺动力学模拟中发现的湍流能量通量有很强的相关性。事实上，能量通量被发现与可用能量成正比，大约是3/2美元的幂，这是人们从一个简单的论点中所期望的。我们进一步研究了可用能量如何分布在不同的弹跳井中，发现深度捕获的电子通常对可用能量贡献最大。最后，我们研究了可用能量对梯度强度的依赖性，并发现了仿星器和托卡马克的弱驱动和强驱动机制之间的重要差异。

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引用次数: 3

Simulation study of the influences of beryllium on the tokamak start-up process 铍对托卡马克启动过程影响的模拟研究

3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-10-01 DOI: 10.1017/s002237782300106x

Yanli Peng, Yan Qiu, Shiqiu Zhao, Shali Yang

Tokamak start-up is strongly dependent on the state of the initial plasma formed during plasma breakdown. To acquire a better understanding of the process and to estimate the influence of the impurity of beryllium on the ohmic heating tokamak start-up process, one-dimensional particle-in-cell coupled with a Monte Carlo collision method has been developed. The main aim is to investigate the plasma performance under various amounts of beryllium with different discharge parameters. Tokamak breakdown with the impurity of beryllium in the ohmic heating strategy has been simulated. The simulation results show that with the impurity of beryllium, the increase of plasma density is suppressed compared with the case without beryllium. The breakdown time is delayed by the impurity. Moreover, the successful breakdown has a much higher requirement on discharge parameters with a low electric field operational scenario, since in the low electric field discharge the influence of beryllium impurity is greater. As the plasma density increases, the effect of beryllium impurity on plasma becomes more critical. It indicates that impurities cannot be neglected in the high plasma density.

托卡马克的启动强烈依赖于等离子体击穿过程中形成的初始等离子体的状态。为了更好地理解这一过程，并估计铍杂质对欧姆加热托卡马克启动过程的影响，本文建立了一维细胞内粒子耦合蒙特卡罗碰撞方法。主要目的是研究不同铍用量和放电参数下等离子体的性能。模拟了在欧姆加热策略下含铍杂质的托卡马克击穿。模拟结果表明，与不含铍的情况相比，含铍杂质的等离子体密度的增加受到抑制。杂质会延迟击穿时间。此外，在低电场情况下，由于铍杂质对放电参数的影响更大，成功击穿对放电参数的要求要高得多。随着等离子体密度的增加，铍杂质对等离子体的影响变得越来越严重。这表明在高等离子体密度中杂质是不可忽视的。

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引用次数: 0

An adjoint-based method for optimising MHD equilibria against the infinite-n, ideal ballooning mode 一种针对无限n理想气胀模式优化MHD平衡的伴随方法

3区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Journal of Plasma Physics

Pub Date : 2023-10-01 DOI: 10.1017/s0022377823000995

Rahul Gaur, Stefan Buller, Maximilian E. Ruth, Matt Landreman, Ian G. Abel, William D. Dorland

We demonstrate a fast adjoint-based method to optimise tokamak and stellarator equilibria against a pressure-driven instability known as the infinite- $n$ ideal ballooning mode. We present three finite- $beta$ (the ratio of thermal to magnetic pressure) equilibria: one tokamak equilibrium and two stellarator equilibria that are unstable against the ballooning mode. Using the self-adjoint property of ideal magnetohydrodynamics, we construct a technique to rapidly calculate the change in the eigenvalue, a measure of ideal ballooning instability. Using the SIMSOPT optimisation framework, we then implement our fast adjoint gradient-based optimiser to minimise the eigenvalue and find stable equilibria for each of the three originally unstable equilibria.

我们展示了一种快速的基于伴随的方法来优化托卡马克和恒星平衡对抗压力驱动的不稳定性，称为无限- $n$理想气球模式。我们提出了三个有限的- $beta$(热压与磁压之比)平衡:一个托卡马克平衡和两个对气球模式不稳定的恒星平衡。利用理想磁流体力学的自伴随性质，构造了一种快速计算理想气胀不稳定性指标特征值变化的方法。使用SIMSOPT优化框架，我们实现了基于梯度的快速伴随优化器，以最小化特征值，并为三个最初不稳定的平衡中的每一个找到稳定的平衡。

引用次数: 0

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