Reports of electropolishing implementation for quarter-wave resonators

At the Tokai Tandem Accelerator of JAEA, researches on nuclear physics, nuclear chemistry, material irradiation, etc. using heavy ion beams are conducted. A superconducting booster has been installed in the latter part of the tandem to increase the beam energy by 2 - 3 times, but it has been out of service for a long time. The specifications of this superconducting booster are model = coaxial quarter wave resonator (QWR), optimum beam speed = 10% of the speed of light, and acceleration electric field = 5.0MV / m (a) 4W. Currently, we are working on restarting this facility, and we are considering electro-polishing of the preliminary superconducting cavity in preparation for conducting various tests. This cavity is made of a niobium-copper clad plate and has a large opening at the bottom, which allows it to be electro-polished again. This time, Marui Galvanizing Co., Ltd. and Japan Atomic Energy Agency jointly examined the equipment and conditions for QWR type superconducting cavity inner surface electro-polishing, conducted electro-polishing, and evaluated the surface and cavity performance after polishing. In this article we will report the result. (author)