• P.V. Avrakhov, A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• M. Ge, I.G. Gonin, T.N. Khabiboulline, J.P. Ozelis, A.M. Rowe, N. Solyak, G. Wu, V.P. Yakovlev
  Fermilab, Batavia
• J. Rathke
  AES, Medford, NY

Use of a superconducting travelling wave accelerating (STWA) structure with a small phase advance per cell rather than a standing wave structure may provide a significant increase in the accelerating gradient in the ILC linac. For the same surface electric and magnetic fields the STWA achieves an accelerating gradient 1.2 larger than TESLA-like standing wave cavities. In addition, the STWA allows longer acceleration cavities, reducing the number of gaps between them. However, the STWA structure requires a SC feedback waveguide to return the few hundreds of MW of circulating RF power from the structure output to the structure input. A test single-cell cavity with feedback was designed and manufactured to demonstrate the possibility of a proper processing to achieve a high accelerating gradient. The first results of high-gradient tests of a prototype 1.3 GHz single-cell cavity with feedback waveguide will be presented.