Advantages of traveling wave resonant antennas for fast wave heating systems

The resilience of a maximally flat externally coupled traveling wave antenna (TWA) is contrasted with the sensitivity of a simple directly driven resonant loop array to vacuum and plasma conditions in DIII-D. We find a unique synergy between standing and traveling wave resonant TWA components. This synergy extends TWA operation to several passbands between 60 and 120 MHz, provides 60°–120° tunability between elements within a 1–2 MHz bandwidth and permits efficient and continuous operation during ELMing H-mode.