Computational modeling of a traveling wave array antenna for exciting Alfven eigenmodes in DD tokamaks

Traveling wave array (TWA) antennas have potential advantages over individually phased ICRF antennas for tokamak heating as the fusion community progresses toward demonstration power plant machines. These advantages include improved load resistance to plasma conditions, simpler feed routing management and a more directed power spectrum. TWAs have been used on DIII-D for helicon current drive and an ICRF TWA is currently being commissioned and built for WEST. Here, engineering and physics simulations for a TWA designed to study Alfven eigenmode (AE) excitation by fast particles in DIII-D is presented. The physics scenario uses moderately high harmonic (~ 4 - 9) heating of neutral beam deuterium particles to accelerate them to hundreds of keV to excite AEs in DIII-D, allowing for a DD tokamak like DIII-D to replicate reactor-relevant fast particle conditions experimentally. COMSOL and Petra-M finite element (FE) tools have been used to study the effects of placing the TWA on the high field side of DIII-D, which has advantages over the low field side including more quiescent plasma conditions aiding in RF coupling and lower heat loads. Image current reduction via center-feeding the TWA is also investigated. In addition to FE tools, the full wave code AORSA is used to investigate the physics scenario, and GENRAY/CQL3D are used to build fast particle distribution functions which are fed to the AE instability code FAR3d to investigate the excited mode structure. Preliminary results for this workflow are presented.