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MOBA07 |
Lessons Learned From Nitrogen Doping at JLab - Exploration of Surface Resistance and Quench Field Trade-Offs With Varied Interstitial Atom Diffusion of Niobium Cavity Surfaces | |
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Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and by the LCLS-II Project under DE-AC02-76SF00515. Interstitial diffusion of atomic species into the surface of niobium has been found to yield significantly reduced srf surface resistance and lowered quench fields. This talk summarizes systematic efforts to explore the trade-offs of these phenomena with a goal of learning how to maximize Q0 in the 30 MV/m regime. The talk also summarizes N-doped cavity progress at JLab for LCLS-II. |
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Slides MOBA07 [3.052 MB] | |
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| MOPB035 | Nature and Implication of Found Actual Particulates on the Inner Surface of Cavities in a Full-Scale Cryomodule Previously Operated With Beams | 164 |
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| Field emission in an SRF cavity is often the result of small foreign particulates lodging on the cavity inner surface. To avoid these particulate field emitters, careful cleaning and handling of individual cavities and clean room assembly of cavity strings are common practice. Despite these elaborate processes, some particulates persist to stay on the final surface of a beam-ready cavity. Moreover, as will be shown in this contribution, new particulates accumulate after a cryomodule is placed in the accelerator tunnel. The nature of these accumulated particulates on the inner surface of a beam-accelerating cavity is largely unknown for two reasons: (1) lack of access to such surfaces; (2) lack of a workable procedure for investigation without destroying the cavity. In this contribution, we report the first study on found actual particulates on the inner surface of 5-cell CEBAF cavities in a full-scale cryomodule previously operated with beam. The nature of the studied particulates is presented. The implication of the findings will be discussed in view of reliable and efficient operation of CEBAF and future large-scale SRF accelerators. | ||
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