Superconducting travelling wave ring with high gradient accelerating section

Use of a superconducting travelling wave accelerating (STWA) structure [1] instead of a standing wave cavity has major advantages in increasing the accelerating gradient in the ILC. In contrast with standing wave cavity STWA requires feedback loop, which sends wave from the structure output to input, making a superconducting travelling wave ring (STWR). One or few input couplers need to excite STWR and compensate power dissipations due to beam loading. To control travelling wave regime in the structure two independent knobs can be used for tuning both resonant ring frequency and backward wave. We discuss two variants of the STWR with one and two feed couplers.