SRF2015 - List of Keywords (survey)

Paper	Title	Other Keywords	Page
MOPB059	Field Emission Investigation of Centrifugal-Barrel-Polished Nb Samples	cavity, site, vacuum, electron	237
	S. Lagotzky, G. Müller Bergische Universität Wuppertal, Wuppertal, Germany A. Navitski DESY, Hamburg, Germany A.L. Prudnikava, Y. Tamashevich University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Funding: This work was funded by BMBF project 05H12PX6. 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. 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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Paper

Title

Other Keywords

Page

MOPB059

Field Emission Investigation of Centrifugal-Barrel-Polished Nb Samples

cavity, site, vacuum, electron

237

S. Lagotzky, G. Müller
Bergische Universität Wuppertal, Wuppertal, Germany
A. Navitski
DESY, Hamburg, Germany
A.L. Prudnikava, Y. Tamashevich
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: This work was funded by BMBF project 05H12PX6.
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.
*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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