Antenna Design And Calculation For The Lower Hybrid Wave System On HL-2M

HL-2A is one of major tokamak devices in China. At present, it is operated at parameters which have reached the design limit. Therefore, The plan to upgrade and reconstruct the HL-2A to the HL-2M is scheduled. Lower hybrid waves (LHW) is one of the important methods of current drive in tokamaks and the antenna system which plays a key role in wave energy coupling to the plasma is very important. The LHW antenna system on the HL-2A is not specially designed, which is just moved from the HL-1M device. Now, for the HL-2M with quite different parameters from the HL-2A, it becomes urgent to design a new LHW antenna system. With this new LHW system, moreover, it is also necessary to calculate the antenna spectrum and the LHW energy coupling efficiency to the plasma.The contents of the dissertation is displayed as follows.1) Present situation of the LHW system at the HL-2A is introduced. Results of the LHW experiment on the HL-2A in recent years are analyzed.2) According to the domestic technique level and the estimated operation parameters on the HL-2M, a new LHW antenna system on the HL-2M is designed, which contains grill array, transition section, flange, ceramic window, phase shift section, vacuum system and brace structure. In addition, a new idea of quasi-whole-spectrum-controlled antenna is also considered. Comparing to the former design, the advantage and disadvantage of the latter one is discussed.3) Spectrum and reflection of the designed antenna is calculated and analyzed using a Brambilla antenna code. The influence of antenna parameters, such as phase difference between two adjacent waveguides, phase difference between two adjacent grills, electron density gradient at the antenna aperture and distance from antenna aperture to the plasma, on spectrum and reflection is discussed.4) Energy couping efficiency and current driving effect with the designed antenna system is calculated using a code from the two-dimensional Fokker-Planck equation with the relativistic effect. The influence of some input parameters, such as the diffusion coefficient, the maximum and minimum N∥of the peak in the spectrum, electron and ion temperature, the effective charge number, on energy couping efficiency and current driving effect is discussed.Based on the design in the dissertation, the LHW antenna system will be fabricated on the HL-2M device. Also, calculations of power spectrum and coupling efficiency base on the designed antenna system will support the LHW experiments in future.