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| Title | Field Emission Investigation of Centrifugal-Barrel-Polished Nb Samples | |||||
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| Abstract | Actual and future SRF-accelerators require high accelerating gradient Eacc and quality factor Q0, which are often limited by enhanced field emission (EFE)* caused by surface roughness or particulates**. Various expensive surface preparation techniques (e.g. BCP, EP, HPR etc.) have been developed to obtain the required surface quality and remove the emitters. Recently, centrifugal barrel polishing (CBP) has been reconsidered to obtain a comparable surface roughness as EP with less effort***. We have started to investigate Nb samples, which were prepared as coupons in a single cell 1.3 GHz cavity by an optimized five step CBP process with a final dry ice cleaning. EFE maps showed the first emitter (1 nA) at 60 MV/m, and 32 emitters at 110 MV/m. SEM/EDX analysis of the emitting sites revealed many Al2O3 inclusions with sharp edges. Therefore, subsequent BCP (~20 μm removal) was applied to the sample. Surface analysis as well as EFE characterization of CBP treated Nb coupons with/without BCP step will be presented. | |||||
| Footnotes & References | *D. Reschke et al., THPP021, LINAC14. **A. Navitski et al., PRSTAB 16, 112001 (2013). ***C.A. Cooper, L.D. Cooley, Supercond. Sci. Technol. 26, 015011 (2013). |
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| Funding | This work was funded by BMBF project 05H12PX6. | |||||
| Paper | download MOPB059.PDF [1.808 MB / 5 pages] | |||||
| Conference | SRF2015, Whistler, BC, Canada | |||||
| Series | International Conference on RF Superconductivity (17th) | |||||
| Proceedings | Link to full SRF2015 Proccedings | |||||
| Session | Poster Session | |||||
| Date | 14-Sep-15 14:20–17:30 | |||||
| Main Classification | Fundamental SRF R&D - Bulk Nb | |||||
| Keywords | cavity, site, vacuum, survey, electron | |||||
| Publisher | JACoW, Geneva, Switzerland | |||||
| Editors | Robert E. Laxdal (TRIUMF, Vancouver, BC, Canada); Jana Thomson (TRIUMF, Vancouver, BC, Canada); Volker RW Schaa (GSI, Darmstadt, Germany) | |||||
| ISBN | 978-3-95450-178-6 | |||||
| Published | December 2015 | |||||
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