JLAB, Newport News, Virginia
KEK, Ibaraki
GUAS/AS, Ibaraki
We report the results of surface characterization of niobium samples electropolished together with single-cell niobium cavities. These witness samples were located in three regions of the cavity, namely at the equator, the iris and the beam-pipe respectively. Auger electron spectroscopy (AES) was utilized to probe the chemical composition of the topmost four atomic layers. Scanning electron microscopy with energy dispersive x-ray for elemental analysis (SEM/EDX) was used to observe the surface topography and chemical composition at the micrometer scale. A few atomic layers of sulfur (S) were found covering the samples non-uniformly. Niobium oxide granules with a sharp geometry were observed on every sample. Some Nb-O granules appeared to also contain sulfur.
KEK, Ibaraki
JLAB, Newport News, Virginia
GUAS/AS, Ibaraki
In this article, two subjects would be described. the first subject is on the production of stains on the surface of Nb sample plates in Electro-polishing (EP) process and the second subject is on the development of defects/pits in the EP process on the surface of a Nb sample plate. Recently, some 9-cell cavities were treated with new EP acid at KEK and the performance of these cavities were limited by heavy field emissions. On the inside surface of these cavities, brown stains were observed. We made an effort to reproduce the brown stains on Nb sample plates with an EP setup in laboratory with varying the concentration of Nibium in the EP acid. We found that the brown stains would appear only when processed with new EP acid. In the second subject, we made artificial pits on the surface of a Nb-sample plate and observed the development of the pits after each step of 30um-EP process where 120um was removed in total by the EP process. This article describes these series EP-tests with Nb sample plates at KEK.
KEK, Ibaraki
CEA, Gif-sur-Yvette
JLAB, Newport News, Virginia
GUAS/AS, Ibaraki
The Electro-Polishing (EP) process is the best candidate of final surface treatment for the production of ILC cavities. Nevertheless, the broad distribution of the gradient caused by field emitters in cavities is sitll a serious problem for the EP process. A candidate source of field emitter is the sulfur component which is produced in the EP process and remains the inner-surface of cavities. We studied the effect of Ethanole- and degreaser-rinse processes after the EP process by a unique method. Moreover, we tried to test the sponge cleaning as the post-EP process to remove the field emitter inside the cavcity. This article describe the results of series tests of the post-EP process at KEK.