Research on Advanced Tokamaks using Dynamic Ergodic Divertorp

(1)改进了DED实验的托卡马克操作采用IGBT逆变电源和电容组相结合的方式构建了欧姆线圈电源。低q和破坏性放电可以得到再现。安装了径向列阵磁力计来测量外部施加的旋转螺旋磁场和内部磁场在中断时的穿透性。详细研究了托卡马克等离子体对外加旋转螺旋磁场的动态响应。制备了一种200 MHz低混合波加热系统，以改善DED的旋转驱动。目前对天线耦合和电子加热特性进行了研究。(2)等离子体电流调制抑制磁岛生长研究了环形等离子体电流快速调制以改变局部q值，并研究了等离子体电流调制对磁岛形成的影响。外加螺旋磁场时，等离子体电流调制能较好地抑制外加螺旋磁场引起的磁扰动。结果表明，对磁共振表面进行快速扫描可以抑制磁岛生长。而在低q放电（q ~ 3）中自发激发的磁扰动和磁岛没有得到明显抑制。(3)内部磁结构在重大破坏过程中的动力学利用内部磁阵列研究了由撕裂模式引起的破坏过程中内部磁场的动态行为。结果表明，在电流淬火刚开始时，内层极向磁场急剧下降（~ 10μs <<电流扩散时间），导致电流密度曲线趋于平缓。内部磁场经过极向磁场的振铃振荡（200kHz）后又突然下降，开始缓慢增加。现在已经进行了内部磁性结构的详细测量。少

(1)Improvement of Tokamak Operation for DED ExperimentsAn ohmic coil power supply has been built by combining an IGBT inverter power supply and a capacitor bank. Low q and disruptive discharges can be obtained reproducibly. Radial array magnetic proves have been installed to measure the penetration of the externally applied rotating helical magnetic field and the internal magnetic field during disruptions. The dynamic response of the tokamak plasma against the externally applied rotating helical magnetic field has been studied in detail. A 200 MHz lower hybrid wave heating system has been prepared to improve the rotation drive by DED. Now the antenna coupling and electron heating characteristics are studied.(2)Suppression of Island Growth by Plasma Current ModulationThe toroidal plasma current is modulated quickly to change the local q value and the effects of the plasma current modulation on the magnetic island formation were studied. When the external helical magnetic field is applie … More d, the plasma current modulation strongly suppresses the magnetic perturbation induced by the externally applied helical magnetic field. It is shown that a fast scan of the magnetic resonance surface can suppress the magnetic island growth. But spontaneously excited magnetic perturbations and islands in low q discharges(q〜3) were not suppressed significantly.(3)Dynamics of the Internal Magnetic Structure during Major DisruptionDynamic behavior of the internal magnetic filed during disruptions induced by tearing modes has been studied using an internal magnetic prove array. It is shown clearly that a very rapid drop (〜10μs << current diffusion time) of the poloidal magnetic field at an inner layer has been observed at just start of current quench, resulting a flattening of the current density profile. The internal magnetic field starts to increase slowly after the ringing oscillation (200kHz) of poloidal magnetic field following a sudden drop again. Now detail measurements of the internal magnetic structure have been carried out. Less