Preliminary Design of the Alfv\'en Antennas on the J-TEXT Tokamak

Research on Alfv\'en waves and Alfv\'en eigenmodes(AEs) is of importance in tokamak plasma physics, such as investigation of interaction between energetic particles and AEs, turbulence and anomalous transport due to AEs, and so on. In order to study the Alfv\'en eigenmode excitation, damping features and the interaction between AEs and plasma transport, an Alfv\'en antennas system is designed for the J-TEXT tokamak. The system can generate high frequency magnetic field aiming to excite the AEs, especially toroidal Alfv\'en eigenmodes (TAE). For a typical J-TEXT plasma (BT$=$ 1-2.2 T,ne $=$ 3-6$\times$10$^{19}$m$^{-3}$), the computed gaps in the Alfv\'en continua range from 300 to 500 kHz, with respect to the Alfv\'en waves dispersion relation [1]. Three pairs of antennas are designed at different toroidal angles respectively on the low field side. Each pair consisting of two coils installed with angles of $+$/- 45$^{\circ}$ off the mid-plane along the poloidal direction. With this system, magnetic field components of mode number m$=$1-10, n$=$1-20 can be produced. The calculations show that the magnetic field in the LCFS can reach $\sim$ 10Gs totally while about $\sim$ 0.5Gs for each mode number, with the coil current of 20A. \\[4pt] [1] Zonca F. Chen L. 1996 Physics of Plasmas 3 323.