Studies on the Production and Upgrading of Confinement Characteristics of Spherical Tokamaks by Means of Merging Effect of Compact Torus Plasmas

在过去的15年里，东京大学的TS-3装置被用来研究各种致密环和球形托卡马克(CT/ST)，特别是与它们的合并形成和加热有关的托卡马克。这些研究包括磁重联实验、场反转组态(FRC)的合并形式、超高β球形托卡马克的合并形式以及外环向场快速应用于FRC的合并形式。这些实验的成功运行使我们能够构建一个放大的合并设备，即TS-4设备。新装置TS-4包含一对普林斯顿S-1型(大半径0.5m)用于感应等离子体形成的内部极向磁芯，一个中心线圈组件，包括用于Q值控制和等离子体维持的外部环向场线圈和OH线圈。TS-4的初步运行(自2001年以来)已经成功地展示了…与过去在TS-3机上观察到的两个球面的共螺度合并和反螺旋度合并一样，更多的是e螺旋度合并。与TS-3的结果相对照，在没有外环磁场的情况下，TS-4中的反螺旋度合并揭示了内环向磁场的相当缓慢的湮灭，澄清了与以前在TS-3机器中观察到的不同的形成高βFRC的性质。弱外环场中的反螺旋度合并，即低Q ST和RFP的合并，使合并的紧致环瞬间松弛成具有很高的β值的低Q球状托卡马克。另一方面，在较强的外环向场中，只有ST的共螺旋度合并被成功地操作。观察到，当外环向场增加到某一临界值以上时，即使在完全自由边界的情况下，ST的稳定性也变得非常明显，这与低n环向模不稳定性的消失有关。CT/ST合并操作的这些性质鼓励我们继续进行紧凑型聚变反应堆的新提议，该反应堆在合并效应的帮助下用于初始等离子体生产和结构的稳态维护。较少

For the past fifteen years, the TS-3 device at the University of Tokyo has been utilized to study a great variety of Compact Tori and Spherical Tokamaks (CT/ST's) particularly in association with their merging formations and heating. The studies have included the magnetic reconnection experiments, the merging formations of the Field Reversed Configurations (FRC), and the merging formations of ultra high beta spherical tokamaks with rapid application of the external toroidal field to the FRC. The successful operations of these experiments enabled us to construct an up-scaled merging device, namely, the TS-4 device. The new device TS-4 contains a pair of internal poloidal flux cores of the Princeton S-1 type (major radius 0.5m) for the inductive plasma formation, a center coil assembly, containing both of the external toroidal field coils and the OH coils, for the q value control and for the plasma sustain. The initial operations of the TS-4 (since 2001) have successfully demonstrated th … More e cohelicity merging and the counter-helicity merging of two spheromaks as have been observed in the TS-3 machine in the past. Constrasting to the TS-3 results, the counter helicity merging in TS-4 without the external toroidal field revealed rather slow annihilations of the internal toroidal magnetic field, clarifying different natures of the formation of a high beta FRC from those observed in the previous TS-3 machine. The counter helicity merging in a weak external toroidal field, namely, the merging of the low q ST and the RFP, makes merged compact toroids relax transiently to low q spherical tokamaks with a very high beta value. On the other hand in a strong external toroidal field, only the cohelicity merging of ST's has been successfully operated. It has been observed that when the external toroidal field is increased above the certain critical value, the stabilization of ST even with a complete free boundary becomes very clear in association with the disappearance of the low n toroidal mode instabilities. These natures of the merging operations of CT/ST's encourage us to proceed with the novel proposal of compact fusion reactors that are assisted by the merging effect for the initial plasma production and steady state maintenance of the configuration. Less