【作者】 饶波；

【导师】 于克训； 虞清泉；

【作者基本信息】 华中科技大学 ， 电气工程， 2013， 博士

【摘要】 撕裂模是托卡马克等离子体中普遍存在的一种不稳定性,其直接表现是在有理磁面形成磁岛。撕裂模磁岛的存在将增强等离子体在有理面附近的径向输运,导致约束性能变差。此外,托卡马克中普遍存在误差磁场,其与磁岛相互作用可能产生误差场锁模,引起等离子体大破裂。因此,撕裂模控制是托卡马克运行中十分关键的问题。外加扰动磁场可与撕裂模发生共振作用,该作用是直接的电磁作用过程,反应速度快,很有希望用在撕裂模的反馈控制上。研究外加扰动磁场对撕裂模的影响是抑制磁岛宽度或驱动磁岛转动的前提基础。本文根据物理实验需求,基于单个鞍形线圈的磁场特征和傅里叶分解的性质,直接从频域出发,设计了J-TEXT动态扰动场线圈(DRMP),产生的磁场模式单纯且可转动,非常适合于扰动场直接影响撕裂模的研究。论文将线圈设计成多层结构,同时线圈外壳不形成回路且与真空室绝缘,很好地解决了真空室内部线圈设计中的真空、绝缘、散热、强电磁应力和交流激励下的涡流屏蔽等难点问题。DRMP线圈可分别产生模式较纯的2/1和1/1扰动磁场,直流工作模式下在等离子体边界产生的最大2/1扰动磁场可达到2.54Gs/kA,交流工作模式下可产生转动的扰动磁场,转动频率可达10kHz。在考虑真空室的衰减情况下,线圈在等离子体边界能产生约0.5Gs/kA的2/1转动扰动磁场。本文利用所设计的扰动场线圈,在J-TEXT上开展了一系列物理实验研究,观察到了外加共振扰动场锁模、抑制撕裂模、抑制后锁模和模穿透等现象。研究获得了锁模和抑制的频率响应区间,低频的撕裂模容易被扰动场锁模,而高频撕裂模容易被抑制。本文还通过扫描SRMP的2/1扰动磁场的空间相位,测量得到了J-TEXT装置误差场的2/1分量。利用Fitzpatrick的模型进行数值计算,很好地解释了这些现象,同时这些现象与磁流体数值模拟结果吻合很好,增进了我们对外加扰动场影响撕裂模作用机理的理解。更重要的是,本文利用转动扰动场锁模磁岛,使磁岛与扰动场同步转动,实现了磁岛的驱动,同时利用解析理论对现象进行了解释,并与电机模型作了对照。扰动场作用下的抑制和磁岛转动加速的现象为撕裂模的主动控制提供了很好的实验依据。更多还原

【Abstract】 Tearing mode is a commonly existed instability in the tokamak plasmas, and its direct result is formation of the magnetic island. The transport in the magnetic island is very strong, which results in a large reduction of plasma temperature and density, consequently an aparent loss of confinement More serious is that if the magnetic island grows to a certain large level, it will cause damages of the magnetic surface structure and then major disruption. Investigating the tearing mode characteristics and finding practical control method is a key issue in future tokamaks and fusion reactors. Tearing mode carries magnetic perturbations with the same helicity as the equlibrium magnetic field line. An externally exerted magnetic perturbation with the same helicity is resonant with the tearing mode and may amplify or attenuate the perturbation. The attenuation of the perturbation indicates the suppression of the tearing mode and improvement of the plasma confinement. The interactions between the magnetic perturbation and the tearing mode are direct electromagnetic procedures and are fast, which makes the external magnetic perturbation is a promising method to control the tearing mode. However, how to make the external perturbation field decrease the tearing mode rather than amplifying it, the thorough understanding of the mechanism is required.To understand the mechanism of the interaction between the tearing mode and the perturbation field, and also to do some preliminary research about tearing mode control, a set of resonant magnetic perturbation (RMP) coils designed on the original TEXT-U tokamak is reconstructed on J-TEXT and now is named as SRMP. SRMP mainly produces m/n=2/1or3/1dominant resonant static perturbation. Because the tearing mode is always rotating in the plasma, a rotating RMP will interact with the tearing mode more intensively and is more flexible for tearing mode control. Basing on the mode structure of a single saddle coil and the properties of the Fourier Transform, a new set of RMP coils named as DRMP is designed and constructed. DRMP is installed inside the vacuum vessel and produces rotating or static2/1or1/1magnetic perturbations.A lot of RMP experiments have been carried out on the J-TEXT tokamak by using SRMP and DRMP. Mode locking, mode suppression and field penetration are all observed. The results indicate that the tearing mode with a low initial frequency can easily be locked by RMP, while a high frequency tearing mode can be suppressed obviously. Moreover, locked mode after mode suppression has been observed, which has been also found in the numerical simulation. The coincidence of the experimental results, numerical simulation and the analytic calculation verified the understanding of the mechanism of the interaction between RMP and the tearing mode, and also provide a foundation for future tearing mode control. The experiments and the analytic calculation carried out in this paper are the foundation of the tearing mode control.更多还原