Development of TWA mock-up for TITAN

The challenge of tokamak auxiliary heating method ICRH is to couple large amount of power through the plasma boundary, where an evanescence layer has to be crossed, without exceeding the voltage standoff at the antenna. Travelling Wave Array antenna has been proposed for ICRH of future fusion reactor such as DEMO in view to decrease the antenna power density. However, so far the voltage standoff of a TWA antenna in the ICRH frequency range (30-60 MHz) has never been demonstrated. A TWA mock-up has been designed and will be tested in the CEA/IRFM testbed TITAN to assess its compatibility to RF high power operation. In this paper, the main characteristics of the TWA mock-up are reported in detail. In addition, some near-field RF analyses are presented, containing reflection characteristics, port voltage, electric field and k(//) spectrum. Meanwhile, the structural evaluation of the antenna during its lifting process is carried out to check with safety requirements. The assembly strategy of the whole structure is also explained elaborately to ensure the fluency and correct integration of the TWA mock-up. Finally, the RF assessment of antenna straps critical dimensions is briefly described.

Automated summary

The paper discusses the challenges and solutions of using a Travelling Wave Array antenna in tokamak auxiliary heating, presenting the design characteristics and RF analysis of the TWA mock-up, along with testing and evaluation processes.