Study on the elucidation of appearance and growth mechanism of magnetic islands and their active control in torus plasmas

研究了与新经典撕裂模式（ntm）相关的磁岛在其发生和演变过程中的结构。发现NTM岛屿是由与另一种不稳定因素相关的小崩溃引发的，除了没有可检测到的不稳定因素。研究发现，坍缩触发NTM的归一化beta值大于无触发NTM的归一化beta值，且前一种情况下模态位置的压力梯度更陡。等离子体旋转突然减慢时的磁岛宽度大于磁岛宽度减小后等离子体开始旋转时的磁岛宽度。这表明在模式锁定和解锁的岛宽中存在滞后。磁岛主动控制装置双频回旋管的研制取得了进展，其标称值的实现具有良好的前景。

Structure of magnetic islands associated with neoclassical tearing modes (NTMs) during their onset and evolution has been investigated. The NTM islands were found to be triggered by a small collapse associated with another instability, in addition to onset without detectable instabilities. It was found that the value of the normalized beta for the collapse-triggered NTM is larger than that for the trigger-less NTM, and that the pressure gradient at the mode location is steeper for the former case. The magnetic island width at which the plasma rotation suddenly slows down is larger than that at the plasma starts to rotate after the island width is decreased. This indicates that there is a hysteresis in the island width for mode locking and unlocking. The development of a device for active control of magnetic islands, a dual-frequency gyrotron, has made progressed, and a good prospect has been obtained toward the achievement of its nominal values.