ICRF Antenna Characteristics and Comparison with 3-D Code Calculation in the LHD

The plasma coupling characteristics and local heat spots of an ion cyclotron range of frequencies (ICRF) antenna in the Large Helical Device (LHD) are compared with the results of 3-D computing simulator code calculation. We studied several dependences of antenna loading resistances with plasma experimentally and observed a clear relation between the maximum injection power and the loading resistance. Realistic three-dimensional configuration of the ICRF antenna was taken into account to simulate the coupling characteristics and the local heat absorption near the ICRF antenna, which has a helically twisted geometry in the LHD. The electromagnetic field distribution and the current distribution on the antenna strap were calculated. We compared the RF absorption distribution on the antenna structure with the temperature rise during steady state operation and found that the temperature rise was well explained by comparing with the model simulation.