Study of Ultra-clean Surface for Niobium SC Cavities

For a TeV energy particle physics, R&D of electron/positron linear colliders has been conducted very hard at many laboratories. Development of high field gradient cavities is one of key issues to realize such a machine. Field emission loading is a dominant phenomenon limiting high field. Particulate contamination on the inner surface is a main source of field emission. In this paper, we report about particulate contamination in wet surface treatments. We discuss particles in chemicals and contamination from environments. Studies with high pressure ultrapure water rinsing and megasonic rinsing are also described.