Wuppertal 2015 – wissenschaftliches Programm
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AKBP: Arbeitskreis Beschleunigerphysik
AKBP 3: RF, Resonators and Applications
AKBP 3.4: Vortrag
Montag, 9. März 2015, 17:30–17:45, BZ.08.06 (HS 1)
Field emission investigations on flat Cu samples before and after surface cleaning — •Stefan Lagotzky1, Pavel Serbun1, Günter Müller1, Tomoko Muranaka2, and Sergio Calatroni2 — 1University of Wuppertal, D-42097 Wuppertal, Germany — 2CERN, Geneva, Switzerland
Enhanced field emission (EFE) resulting in electric breakdowns (BD) is one of the main field limitations of the accelerating structures for the Compact Linear Collider (Eacc = 100 MV/m, Epk/Eacc=2.43). Deep and quantitative understanding of the origin of EFE is therefore important to reduce the conditioning time as well as the final BD rate of these structures. Systematic EFE investigations on Cu samples manufactured in a similar way as the CLIC accelerating structures have revealed an emitter number density up to N= 372 cm−2 at E = 243 MV/m. SEM investigations around the emission sites revealed mainly particulate contaminations as origin of EFE. Removal of such contaminations by cleaning with ionized N2 led to N = 124 cm−2, and a further reduction of N was achieved by applying dry ice cleaning (DIC) in a class 10 cleanroom resulting in N = 29 cm−2. The emission sites that could not be removed by DIC showed onset fields down to Eon = 30 MV/m and field enhancement factors up to β = 360, and SEM investigations revealed mainly accidental scratches and etching pits. Moreover, a strong activation effect of emitters was observed on all samples. A possible breakdown mechanism based on this emitter activation will be discussed.
The work is funded by BMBF project 05H12PX6.