| Paper | Title | Other Keywords | Page |
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| MOYBB3 | Progress in Nb3Sn SRF Cavities at Cornell University | cavity, SRF, accelerating-gradient, site | 37 |
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| Niobium-3 Tin (NbSn) is the most promising alternative material for next-generation SRF cavities. The material can obtain high quality factors (> 1010) at 4.2 K and could theoretically support ~ 96 MV/m operation of a TESLA elliptical style cavity. Current Nb3Sn cavities made at Cornell University achieve high quality factors but are limited to about 17 MV/m in CW operation due to the presence of a surface defect. Here we examine recent results on studying the quench mechanism and propose that surface roughness is a major limiter for accelerating gradients. Furthermore, we discuss recent work on reducing the surface roughness including chemical polishing, modification of material growth, and tin electroplating. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB3 | ||
| About • | paper received ※ 02 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019 | ||
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| WEPLM47 | Analysis of High Field Q-Slope (HFQS) Causes and Development of New Chemical Polishing Acid | cavity, SRF, experiment, niobium | 699 |
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Funding: U.S. National Science Foundation under Grant PHY-1565546. In our previous studies of High Field Q-slope (HFQS) we have concluded that nitrogen contamination from the nitric acid is the main cause of the degradation of the Q in buffered chemical polished cavities. Our conclusion is made based on previously unresolved phenomena which are found from huge amount of published cavity test data, include fine grain, large grain and single crystal cavities treated with EP and BCP. According to this analysis, we have started developing new nitrogen-free chemical polishing acid. Hydrogen peroxide with HF mixture was reported able to react with Nb, and there’s no extra element contamination in it, so we replace the conventional BCP with this mixture to start our study. In this paper, some Nb coupon sample results with new acid will be reported. We complete the first step of developing the new acid and we got the Nb finish roughness no worse than conventional BCP. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM47 | ||
| About • | paper received ※ 13 September 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019 | ||
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| WEPLM63 | Development of a Secondary Sn Source for Nb3Sn Coating of Half-Wave Coaxial Resonator | cavity, niobium, SRF, MMI | 735 |
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| Superconducting thin films have the potential of reducing the cost of particle accelerators. Among the potential materials, Nb3Sn has a higher critical temperature and higher critical field compared to niobium. Sn vapor diffusion method is the preferred technique to coat niobium cavities. Although there are several thin-film-coated basic cavity models that are tested at their specific frequencies, the Half-wave resonator could provide us data across frequencies of interest for particle accelerators. With its advanced geometry, increased area, increased number of ports and hard to reach areas, the half-wave resonator needs a different coating approach, in particular, a development of a secondary Sn source. We are commissioning a secondary Sn source in the coating system and expand the current coating system at JLab to coat complex cavity models. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM63 | ||
| About • | paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019 | ||
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