Experimental Observations of In-situ Secondary Electron Yield Reduction in the Pep-ii Particle Accelerator Beam Line

M. T. F. Pivi b , G. Collet, F. King, R. E. Kirby, T. Markiewicz, T. O. Raubenheimer, J. Seeman SLAC, 2575 Sand Hill Road, Menlo Park, California 94025, USA F. Le Pimpec Paul Scherrer Institute, 5232 Villigen PSI, Schweiz Abstract Beam instability caused by the electron cloud has been observed in positron and proton storage rings and it is expected to be a limiting factor in the performance of the positron Damping Ring (DR) of future Linear Colliders (LC) such as ILC and CLIC [1, 2]. To test a series of promising possible electron cloud mitigation techniques as surface coatings and grooves, in the Positron Low Energy Ring (LER) of the PEP-II accelerator, we have installed several test vacuum chambers including i) a special chamber to monitor the variation of the secondary electron yield of technical surface materials and coatings under the effect of ion, electron and photon conditioning in situ in the beam line ii) chambers with grooves [3] in a straight magnetic-free section and iii) coated chambers in a dedicated newly installed 4-magnet chicane [4] to study mitigations in a magnetic field region. In this paper, we describe the ongoing R&D effort to mitigate the electron cloud