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arXiv 2503.03344physics.plasm-ph
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ASDEX Upgrade 中磁通泵浦的定量磁流体力学模拟

Quantitative Magnetohydrodynamic Modelling of Flux Pumping in ASDEX Upgrade

Haowei Zhang, Matthias Hölzl, Isabel Krebs, Andreas Burckhart, Alexander Bock, Sibylle Günter, Valentin Igochine, Karl Lackner, Rohan Ramasamy, Hartmut Zohm, th… 展开作者

Haowei Zhang, Matthias Hölzl, Isabel Krebs, Andreas Burckhart, Alexander Bock, Sibylle Günter, Valentin Igochine, Karl Lackner, Rohan Ramasamy, Hartmut Zohm, the JOREK team, the ASDEX Upgrade team

AI总结:

本文基于 JOREK 全 MHD 模型定量模拟了 ASDEX Upgrade 混合方案中的磁通泵浦机制,首次揭示了 1/1 MHD 不稳定性驱动的缓慢负发电机效应在电阻扩散时间尺度上维持 q_0 接近 1 并实现无锯齿稳态的关键作用。

摘要:

最近,ASDEX Upgrade(AUG)通过施加非感应电流源和辅助加热实现了无锯齿混合方案 [A. Burckhart et al 2023 Nucl. Fusion 63 126056]。AUG 中的控制实验表明,以异常电流重分布为特征的自调节磁通泵浦机制负责将中心安全因子(q_0)钳制在接近 1 的值,从而阻止锯齿不稳定性的发生。本文基于 JOREK 代码中的双温度、粘滞电阻、全磁流体力学(MHD)模型,对 AUG 混合方案中的磁通泵浦进行了数值和理论研究。为了定量模拟磁通泵浦,我们根据 AUG 实验选择了真实的参数、等离子体位形和源项。在不稳定的 1/1 准互换模的初始饱和阶段(毫秒时间尺度上),q_0 表现出快速的欠阻尼振荡并达到更接近 1 的值,这归因于核心等离子体的自调节和量级为 V/m 的快速发电机效应。在更长的秒级电阻扩散时间尺度上,由 1/1 MHD 不稳定性诱导的量级为 mV/m 的缓慢负发电机效应在磁通泵浦中发挥了有效作用,首次与实验观测结果实现了定量一致。最终饱和的 1/1 MHD 不稳定性表现出准互换模和撕裂模的特征,相关的对流等离子体流速为每秒几米。来自缓慢发电机效应的环向负电场主导性地抵消了正电流驱动,并持续重新分布电流密度和压强。因此,由于等离子体核心中电流密度和压强的低剪切剖面,q_0 被维持在接近 1 的值,系统进入无锯齿且准稳态的螺旋状态。

英文摘要:

The sawtooth-free hybrid scenario has been achieved recently in ASDEX Upgrade (AUG) with applied non-inductive current sources and auxiliary heating [A. Burckhart et al 2023 Nucl. Fusion 63 126056]. Control experiments in AUG suggest that the self-regulating magnetic flux pumping mechanism, characterized by anomalous current redistribution, is responsible for clamping the central safety factor (q_0) close to unity, thereby preventing the sawtooth onset. This work presents a numerical and theoretical investigation of flux pumping in the AUG hybrid scenario based on the two-temperature, visco-resistive, full magnetohydrodynamic (MHD) model with the JOREK code. To quantitatively model the flux pumping, we choose realistic parameters, plasma configurations, and source terms based on AUG experiments. During the initial saturation stage of the unstable 1/1 quasi-interchange mode (on millisecond timescales), q_0 exhibits fast under-damped oscillation and reaches a value closer to unity, which is attributed to the self-regulation of core plasma and the fast dynamo effect on the order of V/m. On the longer resistive diffusion timescale of seconds, the slow negative dynamo effect on the order of mV/m induced by the 1/1 MHD instability plays an effective role in flux pumping, which provides quantitative agreement with experimental observations for the first time. The final saturated 1/1 MHD instability exhibits features of the quasi-interchange mode and tearing mode, and the associated convective plasma flow velocity is a few m/s. The toroidal negative electric field from the slow dynamo dominantly offsets the positive current drive and continuously redistributes the current density and pressure. As a result, q_0 is maintained close to unity due to the low-shear profiles of current density and pressure in the plasma core, and the system enters a sawtooth-free and quasi-stationary helical state.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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