Experimental and theoretical studies of active control of resistive wall mode growth in the EXTRAP T2R reversed-field pinch
Experimental and theoretical studies of active control of resistive wall mode growth in the EXTRAP T2R reversed-field pinch
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DOI：
10.1088/0029-5515/45/7/002
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发表时间：
2005-06
期刊：
影响因子：
3.3
通讯作者：
J. Drake;P. Brunsell;D. Yadikin;M. Cecconello;J. Malmberg;D. Gregoratto;R. Paccagnella;T. Bolzonella-T.-Bol
中科院分区：
文献类型：
--
作者：
J. Drake;P. Brunsell;D. Yadikin;M. Cecconello;J. Malmberg;D. Gregoratto;R. Paccagnella;T. Bolzonella-T.-Bol
在EXTRAP T2R反场箍缩实验中，对阻性壁模进行了主动反馈控制。控制系统包括由磁线圈阵列（测量模式谐波）组成的传感器和由鞍形线圈阵列（产生控制谐波）组成的致动器。闭环（反馈）实验，使用数字控制器的传感器数据的真实的时间傅立叶变换的基础上进行了研究的情况下，反馈增益是恒定的和真实的为所有的谐波（对应于一个智能外壳）和情况下，反馈增益可以设置为选定的谐波，与真实的和复杂的值（目标谐波）。通过对智能壳和目标谐波控制系统的反馈，可以减少占主导地位的RWM的增长。由于阵列中鞍形线圈的环形位置的数量是传感器数量的一半，因此预测并实验观察到控制谐波频谱具有边带。可以用真实的增益控制单个不稳定谐波。然而，如果存在由边带效应耦合的两个不稳定模式谐波，则控制对于真实的增益的效果要差得多。根据理论，复增益对于（缓慢）旋转的RWM给出更好的结果，并且实验支持这一预测。此外，开环实验已被用来观察应用到不稳定，边缘稳定和鲁棒稳定模式的谐振场误差的影响。观察到的场误差影响与薄壁模型一致，其中模式增长与谐振场误差幅度和该模式谐波的壁穿透时间成正比。
Active feedback control of resistive wall modes (RWMs) has been demonstrated in the EXTRAP T2R reversed-field pinch experiment. The control system includes a sensor consisting of an array of magnetic coils (measuring mode harmonics) and an actuator consisting of a saddle coil array (producing control harmonics). Closed-loop (feedback) experiments using a digital controller based on a real time Fourier transform of sensor data have been studied for cases where the feedback gain was constant and real for all harmonics (corresponding to an intelligent-shell) and cases where the feedback gain could be set for selected harmonics, with both real and complex values (targeted harmonics). The growth of the dominant RWMs can be reduced by feedback for both the intelligent-shell and targeted-harmonic control systems. Because the number of toroidal positions of the saddle coils in the array is half the number of the sensors, it is predicted and observed experimentally that the control harmonic spectrum has sidebands. Individual unstable harmonics can be controlled with real gains. However if there are two unstable mode harmonics coupled by the sideband effect, control is much less effective with real gains. According to the theory, complex gains give better results for (slowly) rotating RWMs, and experiments support this prediction. In addition, open loop experiments have been used to observe the effects of resonant field errors applied to unstable, marginally stable and robustly stable modes. The observed effects of field errors are consistent with the thin-wall model, where mode growth is proportional to the resonant field error amplitude and the wall penetration time for that mode harmonic.