|WEPP32 ポスターセッション① 9月2日 ポスター会場 12:40-14:40|
|Analysis and Field Emission Characteristic of Niobium Surface Treated with Electropolishing Process|
○Vijay Chouhan, Yoshiaki Ida, Keisuke Nii, Takanori Yamaguchi (Marui Galvanizing Co., Ltd.), Hitoshi Hayano, Shigeki Kato, Hideaki Monjushiro, Takayuki Saeki (KEK)
Niobium (Nb) coupons in-situ-electropolished (EPed) with an Nb SRF coupon cavity and laboratory EPed Nb samples were analyzed with XPS, SEM, EDX for chemical, morphological and elemental information of their surfaces. The coupons EPed simultaneously showed different peak intensity ratios of Nb0 to Nb5+, different concentrations of O, C and other elements on their top surfaces. The results were related to the number density of particle clusters, which were present on the surface and confirmed to be Nb2O5 by XPS and EDX analyses. Both XPS and EDX analyses revealed that the particles contained C, F, and Cu impurities. Surface analysis results of the laboratory EPed samples were found to be consistent with that of the coupons. Field emission characteristics were measured for the EPed coupon surfaces with two different field emission measurement systems. The surface having particles showed a significantly higher emission current at a lower electric field compared to a relatively clean surface. This article also describes the mechanism of particle formation on the surface and necessary optimized post-EP processes that removed the undesired synthesized particles from the cavity surface.