Experimental investigation and gyrokinetic simulations of multi-scale electron heat transport in JET, AUG, TCV
Experimental investigation and gyrokinetic simulations of multi-scale electron heat transport in JET, AUG, TCV
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JET、AUG、TCV 中多尺度电子热传输的实验研究和回旋模拟
DOI：
10.1088/1741-4326/ac1fa9
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发表时间：
2021
期刊：
影响因子：
3.3
通讯作者：
ITPA Transport & Confinement Group
中科院分区：
文献类型：
--
作者：
A. Mariani;N. Bonanomi;P. Mantica;C. Angioni;T. Görler;O. Sauter;G. Staebler;EUROfusion JET1 Contributors;EUROfusion MST1 Contributors;the ASDEX Upgrade team;the TCV team;ITPA Transport & Confinement Group
像ITER这样以电子加热为主的托卡马克可能会遭受电子温度梯度（ETG）模式不稳定的后果，这可能会产生湍流电子热通量，从而为可实现的电子温度峰值设定上限，导致聚变性能下降。在本文中进行的努力，收集和比较的结果专用等离子体放电在过去几年中在三个主要的欧洲托卡马克，TCV，AUG和JET，通过分析电子热输运的情况下，大概兼容ETG的相关性，这些不稳定性的实际理论理解。通过进行稳态热流扫描和射频加热调制微扰分析，实验研究了电子温度分布对电子热流变化的响应。实验结果面临的数值模拟，从简单的线性gyrokinetic（GK）或准线性运行，非常昂贵的计算非线性多尺度GK模拟，解决离子和电子尺度在同一时间。到目前为止收集的结果倾向于确认先前出现的图片，表明具有适当平衡的电子和离子加热的情况下，具有相似的电子和离子温度和足够大的ETG，可以与ETG对电子热传输的不可忽略的影响兼容。离子加热不仅通过增加离子温度来使ETG不稳定，而且还由于通过快速离子和E × B剪切的协同作用来稳定离子尺度湍流，这在某些情况下与之相关。等离子体杂质对ETG的稳定作用仍在通过多尺度GK模拟进行研究中，并且还需要在电子尺度上对密度和温度波动进行直接实验测量，以最终评估ETG的影响。
Tokamaks dominated by electron heating like ITER could possibly suffer from the consequences of electron temperature gradient (ETG) mode destabilisation, which could develop a turbulent electron heat flux capable of setting an upper limit to the achievable electron temperature peaking, resulting in a degradation of the fusion performance. An effort is carried out in this paper to collect and compare the results of dedicated plasma discharges performed during the last few years at three of the major European tokamaks, TCV, AUG and JET, by analysing the electron heat transport for cases presumably compatible with ETGs relevance, given the actual theoretical understanding of these instabilities. The response of the electron temperature profiles to electron heat flux changes is experimentally investigated by performing both steady state heat flux scans and perturbative analysis by radio frequency heating modulation. The experimental results are confronted with numerical simulations, ranging from simple linear gyrokinetic (GK) or quasi-linear runs, to very computationally expensive nonlinear multi-scale GK simulations, resolving ion and electron scales at the same time. The results collected so far tend to confirm the previously emerging picture, indicating that cases with a proper balance of electron and ion heating, with similar electron and ion temperatures and sufficiently large ETG, could be compatible with a non negligible impact of ETGs on the electron heat transport. The ion heating destabilises ETGs not only by increasing the ion temperature but also thanks to the stabilisation of ion-scale turbulence by a synergy of fast ions and E × B shearing, which are in some cases associated with it. The stabilising effect of plasma impurities on ETGs is still under investigation by means of multi-scale GK simulations, and also direct experimental measurements of density and temperature fluctuations at electron scales would be needed to ultimately assess the impact of ETGs.