CEA, Gif-sur-Yvette
CNRS Orléans, Orléans Cedex 2
A decade after the ‘baking effect” discovery [*], the quest to understand this effect and its correlated question about the High Field Q-slope origin, goes on at Saclay. SIMS analyses and “fast baking” experiments in Oxygen free atmosphere [**] have shown since then that interstitial oxygen diffusion is not involved in baking phenomenon. In this paper we will describe preliminary experiments performed on niobium samples by means of positron annihilation radiation Doppler broadening spectroscopy. Experimental results reveal many vacancy sites and help us to give a new interpretation of the “baking effect”.
[*] “Improvement of Superconducting Cavity Performances”, 6th EPAC (1998): TUP07B
[**] “Optimization of Baking Parameters for Electropolished Cavities”, 13th SRF Workshop(2007): TUP69
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.