FRPI005 　加速構造　 8月2日 国際科学イノベーション棟5階 ホワイエ 10:50-12:50

Parametric Study for Uniform Electropolishing of 1.3 GHz Nine-Cell Niobium Cavity with Dual Acid Flow Mechanism

○Vijay Chouhan, Yoshiaki Ida, Keisuke Nii, Takanori Yamaguchi (Marui Galvanizng Co Ltd, Japan), Hitoshi Hayano, Shigeki Kato, Takayuki Saeki, Hideaki Monjushiro, Motoaki Sawabe (High Energy Accelerator Research Organization, Japan), Hiroki Oikawa (Utsunomiya University, Japan), Hayato Ito (Sokendai, Japan)

The interior surface of a niobium superconducting RF (SRF) accelerating cavity is treated with either horizontal electropolishing (HEP) or vertical electropolishing (VEP) methods, where the cavity is set in the horizontal and vertical positions in the HEP and VEP, respectively. A major challenge in the VEP is non-uniform material removal and surface roughness owing to the accumulation of hydrogen gas bubbles, generated on the cathode surface in the EP process, on the cavity surface. The presence of bubbles on the surface impairs the viscous layer of the electrolyte and enhances EP rate locally. The bubble accumulation was significantly reduced by applying a novel method in which the acid was flown separately in a unique cathode housing and cavity. The effect of this dual flow was observed and EP parameters were studied by monitoring EP currents of the coupons fixed at the different positions of a test nine-cell coupon cavity. The removal asymmetry was reduced with the dual flow process and other optimized parameters. A 1.3 GHz nine-cell SRF cavity processed under the same conditions showed a good SRF performance at a temperature of 2 K.