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

An ultra-high vacuum loadlock system capable of operating at high voltage has been added to the SLC Polarized Electron Gun. The unit incorporates facilities for heat cleaning, activating and measuring the quantum efficiency of photocathodes. A tray of up to four photocathodes can be exchanged without bringing the activation unit or gun up to atmosphere.Low voltage quantum efficiencies of 20% have been obtained for bulk GaAs at 633 nm and 6% for a 0.3 micron GaAs layer at 755 nm. Results for other cathodes as well as operational characteristics are discussed.

Possible remedies for the electron cloud in positron damping ring (DR) of the International Linear Collider (ILC) includes thin-film coatings, surface conditioning, photon antechamber, clearing electrodes and chamber with grooves or slots [1]. We installed chambers in the PEP-II Low Energy Ring (LER) to monitor the secondary electron yield (SEY) of TiN, TiZrV (NEG) and technical accelerator materials under the effect of electron and photon conditioning in situ. We have also installed chambers with rectangular grooves in straight sections to test this possible mitigation technique. In this paper, we describe the ILC R&D ongoing effort at SLAC to reduce the electron cloud effect in the damping ring, the chambers installation in the PEP-II and latest results.