Control of resistive wall modes in the spherical tokamak

Nuclear Fushion

article

Guoliang Xia¹  Yueqiang Liu²  T.C. Hender¹  K.G. McClements¹  E. Trier¹  E. Tholerus¹ 

[1] UKAEA, Culham Science Centre;General Atomics

关键词: spherical tokamak;    resistive wall mode;    kinetic effects;    active control;    plasma flow;   

DOI  :  10.1088/1741-4326/acadf0

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

In this work, the MARS-F/K codes (Liuet al2000Phys. Plasmas73681; Liuet al2008Phys. Plasmas15112503) are utilized to model the passive and active control of then = 1 ( nis the toroidal mode number) resistive wall mode (RWM) in a spherical tokamak (aspect ratioA= 1.66). It is found that passive stabilization of the RWM gives a relatively small increase in normalized beta above the no-wall limit, relying on toroidal plasma flow and drift kinetic resonance damping from both thermal and energetic particles. Results of active control show that with the flux-to-voltage control scheme, which is the basic choice, a proportional controller alone does not yield complete stabilization of the mode. Adding a modest derivative action, and assuming an ideal situation without any noise in the closed-loop, the RWM can be fully stabilized with the axial plasma flow at 5% of the Alfvén speed. In the presence of sensor signal noise, success rates exceeding 90% are achieved, and generally increase with the proportional feedback gain. On the other hand, the required control coil voltage also increases with feedback gain and with the sensor signal noise.

【 授权许可】

Unknown