Traveling Wave Accelerating Structure for A Superconducting Accelerator

We present a superconducting traveling wave accelerating structure (STWA) concept, which may prove of crucial importance to the International Linear Collider. Compared to the existing TESLA cavity design, the traveling wave structure can provide ∼20-40% higher accelerating gradient for the same aperture and the same peak surface RF magnetic field. The recently achieved SC structure gradient of 35 MV/m can be increased up to ∼50 MV/m with the new STWA structure design. The STWA structure is supposed to be installed into the superconducting resonance ring and is fed by one or two couplers (depending on the required input power) with appropriate phase advance to excite a traveling wave inside the structure. We discuss the structure design, optimization of the parameters, tuning requirements and plans for further development.