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T: Fachverband Teilchenphysik
T 82: Quellen / Injektoren
T 82.7: Talk
Monday, March 28, 2011, 18:15–18:30, 30.22: 020
Activation of field emitters on clean Nb surfaces — •Aliaksandr Navitski1, Stefan Lagotzky1, Günter Müller2, Detlef Reschke2, and Xenia Singer2 — 1University of Wuppertal, D-42097 Wuppertal, Germany — 2DESY, D-22603 Hamburg, Germany
Systematic investigations of the enhanced field emission (EFE) from surface irregularities of typical electropolished and high-pressure rinsed Nb samples revealed an exponential increase of the emitter site density with the initial onset surface field (80-160 MV/m) and a strong activation effect, i.e. the final occurrence of EFE at 2-4 times lower surface fields relevant for superconducting XFEL and ILC cavities. Possible explanations for this activation are breakdown across the surface oxide, surface erosion by a local microplasma or de/adsorption effects. Such an emitter activation might also be caused by the usual baking or the rf power processing of cavities. Therefore, we have started a systematic test series with clean large-grain Nb samples based on correlated field emission scanning microscopy (FESM) and high-resolution SEM investigations before and after controlled in-situ heating at temperatures between 120 and 800 degree C. The impact of the baking on the EFE of particulates and surface defects will be discussed.
Förderung durch die Helmholtz-Allianz Physics at the Terascale und das BMBF-Verbundprojekt 05H09PX5.