Optimization of a traveling wave superconducting rf cavity for upgrading the International Linear Collider

The Standing Wave (SW) TESLA niobium-based superconducting radio frequency structure is limited to an accelerating gradient of about 50 MV/m by the critical RF magnetic field. To break through this barrier, we explore option traveling wave (TW) structures. Optimization TW structures was done considering experimentally known limiting electric and fields. It shown that a can have above 70 MeV/m 1.5 times higher than contemporary standing with same other benefit R/Q 2 reduces dynamic heat load factor 2. A method proposed how make multipactor-free. Some design proposals are offered facilitate fabrication. Further increase real-estate (equivalent 80 active gradient) also possible increasing length because group velocity cell-to-cell coupling. Realization work opens paths ILC energy upgrades beyond 1 TeV 3 in competition CLIC. paper will discuss corresponding opportunities challenges.