Electron cloud effects in positron storage rings

This is a review of electron cloud effects/instabilities observed in positron storage rings. Coupled bunch and fast head-tail instabilities caused by an electron cloud have been studied for a long time, and the agreement of experiments and simulations/theory is almost perfect in positron storage rings. Mitigation of the instabilities based on the experiments and simulations have improved the accelerator performance drastically. It is essential to mitigate the instabilities in the present and future positron and proton rings.