Surface analyses of electropolished niobium samples for superconducting radio frequency cavity
(Color online) Preparation of EP at single cell cavity with samples: (a) sample used for EP; (b) Nb SRF cavity drilled with three pairs of holes at critical positions equator, iris, and beam pipe; (c) single cell cavity assembled with samples at EP bed.
(Color online) Analysis system connected with an UHV suitcase via three loadlock chambers. Its base pressure is maintained of the order of .
(Color online) Comparison of XPS spectrums among equator, iris, and beam pipe samples EPed with fresh EP solution, (a) oxygen spectrum, and (b) sulfur spectrum.
(Color online) Comparison of XPS spectrums among equator, iris, and beam pipe samples EPed with aged EP acid with Nb concentration of 7.9 g/l, (a) oxygen spectrum, (b) sulfur spectrum, and (c) fluorine spectrum.
(Color online) Depth profile of iris sample (EPed with aged acid) sputtered up to 5 nm.
SEM images of beam pipe sample. (a) EPed with fresh EP acid. (b) EPed with aged EP acid.
(Color online) Secondary ion images with a resolution of and a color gradation in 40 steps linearly to the ion intensity of sulfur compound. The brightest dots in each image show sulfur concentrations and their compounds locally concentrated with a size of around .
Atomic percentages of the elements present on the samples surface.
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