【作者】 杨旭；

【导师】 刘悦；

【作者基本信息】 大连理工大学 ， 等离子体物理， 2018， 博士

【摘要】 托卡马克中等离子体对三维磁场响应是聚变研究中非常重要的研究课题,包括利用共振磁扰动场控制边缘局域模、误差场修正、等离子体流阻尼、高压强等离子体中共振场的放大、电阻壁模的主动控制和其它磁流体不稳定性。研究已经证实,即使比背景(平衡)磁场小3-4个量级的外加三维场,仍可以对二维轴对称托卡马克等离子体的稳定和约束造成重要的影响,三维扰动场可以通过放大自已,来控制不同的不稳定性。近些年的研究已经证实Type-Ⅰ边缘局域模会对未来托卡马克装置中的壁材料造成重大威胁,ITER装置上现有的壁材料和偏滤器材料只能承受边缘局域模爆发过程中20%的热负荷,因此控制边缘局域模是聚变领域中非常重要的研究课题。目前为止,外加共振磁扰动场是最简单、最有效的方法,可以很好地控制边缘局域模。在DⅢ-D、JET、MAST、ASDEX Upgrade、KSTAR、EAST等托卡马克装置中利用共振磁扰动技术可以很好地缓解和/或抑制边缘局域模,但是由于涉及的物理机制比较复杂,抑制边缘局域模的最终原因和必要条件仍是开放的问题。在建造和运行托卡马克的过程中不可避免地存在非轴对称磁扰动场,尤其是环向模数n=1的误差场可以引起锁模,甚至会造成等离子体大破裂,所以利用外加磁扰动场修正误差场是聚变领域中非常重要的研究课题。在DⅢ-D、JET、MAST、EAST、KSTAR等装置中已经开展了误差场修正的实验。但是由于误差场修正的理论研究需要全环位型,这样才能为托卡马克装置提供更好的误差场修正建议,所以理论上并没有得到很好的发展。利用外加磁扰动控制边缘局域模和修正误差场是很重要的研究课题。所以本文数值模拟与实验相结合,深入地分析实验结果,并解释其中的物理机制。绪论部分主要介绍了不同种类的聚变装置,边缘局域模、利用共振磁扰动场控制边缘局域模和误差场修正的研究进展。第二章简要介绍了 MARS程序及其模型,该程序包含MARS-F、MARS-K和MARS-Q三个版本。介绍了如何利用MARS程序数值模拟环位型下等离子体对外加磁扰动的响应。第三章利用MARS-F程序对DⅢ-D中等离子体对n=2偶线圈结构下的共振磁扰动场响应实验进行数值研究,利用线性等离子体响应模型,分别为电阻、旋转等离子体响应模型和理想、静态等离子体响应模型,该工作的研究目的是理解边界安全因子对等离子体响应的影响。不管是利用电阻、旋转等离子体响应模型还是理想、静态等离子体响应模型,在(q95,qa)空间中,低场区、高场区-A和高场区-B处的极向场都会出现等离子体响应的跳变。同时也观察到,利用电阻、旋转等离子体响应模型得到的跳变会更加明显。大的响应场和X点扰动位移与边缘剥离响应有关,边缘剥离响应也是产生跳变的原因。第四章利用MARS-F程序对EAST中等离子体对三维共振磁扰动场响应实验的数值研究。在考虑等离子体响应时,数值模拟得到的最优线圈相位差与EAST中缓解和抑制边缘局域模的相位差一致。MARS-F模型中最外层有理面处扰动磁场和X点扰动位移的判定方法,既适用于边缘局域模的缓解,也适用于边缘局域模的抑制。第五章利用MARS-F程序对EAST中误差场修正实验进行数值研究。基于使整个等离子体区域电磁矩最小的误差场修正判定方法,给定的n=1固有真空误差场包含多个极向谐波时,利用罗盘扫描法计算预测的2/1误差场可以同时与实验中的奇、偶修正线圈结构下罗盘扫描法的结果一致。而且罗盘扫描法预测的真空误差场与MARS-F程序中给定的误差场不同,该结果对误差场修正实验和利用罗盘扫描法确定固有误差场的方法有了进一步的理解。最后,对现有工作进行总结,并对下一步的工作进行展望。更多还原

【Abstract】 The plasma response to 3D magnetic fields is an important research topic in fusion research,including the edge localized modes(ELMs)control using the resonant magnetic perturbations(RMPs),the error field correction(EFC),the plasma flow damping,the resonant field amplification of high pressure plasmas,the active control of the resistive wall mode(RWM)and other magneto-hydrodynamics(MHD)instabilities.It has recently been realized that,even a small amount of the external 3D fields,of the 3-4 orders smaller than the background(equilibrium)magnetic field,can have profound influence on the stability and confinement of the otherwise 2D axi-symmetric tokamak plasmas.The external 3D fields manifest themselves in controlling various MHD instabilities.During recent years,it has been realized that large ELMs instability,the so-called type-I ELMs,can pose significant danger to the material walls in future tokamak devices.For ITER,the plasma facing components and divertor can only bear 20%of heat loads associated with edge localized mode events.So studies in ELMs mitigation and suppression are important research topics in fusion research.So far the most mature and reliable technique,is the application of RMPs.The RMPs technique has been extensively employed in DIII-D,JET.MAST,ASDEX Upgrade,and recently in KSTAR as well as EAST.ELMs control has been achieved in these devices.Due to various physics mechanisms,which are not fully clear yet at the moment,the ultimate cause and the necessary conditions for ELMs suppression are still open questions.The non-axisymmetric magnetic field perturbations inevitably exist in the tokamak device design and construction due to various sources.In particular,the n=1 error field(EF)can induce mode locking,and the locked mode often leads to the plasma disruption.The EFC using external magnetic perturbation fields in tokamaks is an important research topic in fusion research.The EFC experiments have been carried out in many tokamaks,e.g.DIII-D,JET,MAST,EAST,KSTAR,etc.Despite extensive experimental efforts in understanding the EFC using additional magnetic coils,modelling work is so far limited.This is probably because the EFC modelling is critically involves the geometery.A full toroidal geometry is essential,in order to provide useful recommendations for the optimal correction of the EF in a given device.ELMs control and EFC,using the external magnetic perturbation,are important topics.Simulations are carried out to compare with the experiments.Analyse the results of experiments deeply,and try to understand the physics of ELMs control and EFC.In chapter I,the variety of fusion devices and ITER plan are introduced.The progress of the ELMs.ELMs control using RMPs and EFC are reviewed.In chapter Ⅱ,the MARS code and models are described.The computational tool is the state-of-the-art codes suite MARS-F,MARS-K and MARS-Q.And how to use the MARS code to model the response of the plasma to the external magnetic field in toroidal geometry is introduced.In chapter Ⅲ,we have computationally simulated plasma response to the n=2 even parity RMP in DⅢ-D.using the MARS-F code.This study is based on the linear plasma response,using both the resistive,rotation plasma and ideal,static plasma response models.This work focuses on understanding how the edge safety factor affects computed plasma response.We find that both the resistive,rotation plasma and ideal,static plasma response models show a jump in low field side,high field side-A and high field side-B pickups in(q95,qa)space.It is also shown that transition is more smoothly with ideal,static plasma response model.Furthermore,large edge-peeling component is responsible for both large pickup fields and large plasma displacement near X-point,and the reason of the jump.In chapter Ⅳ,we carry out a modelling of plasma response to 3D external magnetic field perturbations in EAST,using MARS-F code.The modelled results,takeing into account the plasma response,agree well with the experimental observations in terms of the coil phasing for both the mitigated and the suppressed ELMS cases in EAST experiments.Another important finding from the present study is that the field and plasma-displacement-based criteria,derived from the MARS-F model,seem to work not only for ELMs mitigation,but also for ELMs suppression.In chapter Ⅴ,we carry out a modelling of EFC in EAST,using MARS-F code.Assumed n=1 intrinsic vacuum EF with multiple poloidal spectra,the compass scan predicted 2/1 EF,based on minimizing the computed resonant electromagnetic torque,can be made to match well with that of the EFC experiments using both even and odd parity coils.Moreover,the compass scan predicted vacuum EFs are found to be significantly differing from the true intrinsic EF used as input to the MARSF code.While the puzzling result remains to be fully resolved,the results from this study offer an improved understanding of the EFC experiments and the compass scan technique for determining the intrinsic EF.Finally,the summary of this thesis and the future work are presented.更多还原