Münster 1999 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

VA: Vakuumphysik und Vakuumtechnik

VA 6: Ausgasung und Oberflächen

VA 6.4: Vortrag

Dienstag, 23. März 1999, 16:50–17:10, ZH

Influence of Air Exposures on the Secondary Electron Yield (SEY) of Copper — •Christian Scheuerlein¹, Iouri Bojko², Jean-Luc Dorrier³, and Noel Hilleret¹ — ¹CERN, Geneva — ²IPP-MPI, Garching — ³CRPP-EPFL, Lausanne

The performance of particle accelerators may be severely hampered by resonant electron multiplication (multipacting) in the vacuum chamber. Apart from the resonance conditions between the driving electric field of the particle beam and the geometry of the vacuum chamber, multipacting is strongly influenced by the secondary electron yield (SEY) of the involved surfaces. In this context the variation of the SEY of pre-treated polycrystalline OFHC-copper, the candidate surface coating for the Large Hadron Collider, has been studied as a function of exposure to ordinary laboratory air. After a short air exposure of some seconds the maximum SEY of the initially clean surface can be reduced from 1.3 to less than 1.2, due to the oxidation of the copper surface. Subsequent longer air exposures, however, lead to a steady increase of the SEY. Thus, after about 8 days of atmospheric exposure, the maximum SEY increases to a value above 2, which is close to that of the untreated, as received sample.

Based on these measurements a method has been developed which decreases the maximum SEY of technical copper surfaces to a value close to unity.