2010 Volume 7 Issue 3 Pages 199-208
Efforts to produce high gradients in 1.3 GHz superconducting single-cell and 9-cell cavities started around 20 years ago. Many efforts and developments have been made and the TESLA technology became a baseline for cavity fabrication and surface treatment of XFEL and ILC cavities. Continuous effort for high gradient with high yield has been made to reach the ILC specification. However, the ILC goal of 35 MV/m@Q0=8E9 with 90% yield is still a little beyond the present state of the art. In our previous report, the optimization of the electropolishing facility by the chemical analysis, surface analysis and the coupon experiments have been discussed. In this report, research on the physical cleaning method, the optical observation of the cavity inner surface together with quench localization technique, the electromagnetic calculation for defect and a defect removal tool are discussed. Continuous research on gradient performance improvement of the superconducting cavity is in progress at KEK-STF.
