Abstract: Apparatus and methods provide a robust radio frequency (RF) interface for a helix-type traveling wave tube (TWT). As a vacuum device, the RF input to the TWT and the RF output from the TWT are sealed to maintain the vacuum. The disclosed robust RF interface techniques are advantageously less prone to breakage than conventional sealing techniques. In addition, configurations of the disclosed robust RF interface techniques can further exhibit relatively good impedance matches between a TWT and an associated antenna, which can reduce insertion losses and reflection losses, thereby advantageously increasing system RF output power.