Accelerating cavities for the proposed TESLA superconducting electron-positron collider routinely achieve the 25 MV/m accelerating gradient that is required to achieve a collision energy of 500 GeV in a 33 km collider. Now, for the first time, a nine-cell TESLA cavity has achieved 35 MV/m, which would be sufficient to operate the accelerator at 800 GeV.
The secret of this achievement is a collaboration between Hamburg’s DESY laboratory, which is driving the TESLA project, and the KEK laboratory in Japan. Until now, the niobium surface of the TESLA cavities has been chemically etched. Through the DESY-KEK collaboration, the new cavity has been electropolished by the Nomura Plating Company, resulting in a smoother surface. Moreover, baking the cavities at 100°C has been shown to lead to further improvements, with 40 MV/m being reached in single-cell cavities.
An electropolishing facility for TESLA cavities is scheduled to be commissioned at the DESY laboratory in June.
