ELECTRON CLOUD AND SINGLE-BUNCH INSTABILITIES IN THE RELATIVISTIC HEAVY ION COLLIDER

Electroncloudis a leadingmechanismlimitingRHIC in- tensity upgrades. Electron cloud in RHIC is in an interme- diate regime sharing features of both the long-bunch(PSR) and short-bunch (photon factories) machines. Vacuum- pressure rises, transverse tune shifts, and electron flux are observed at injection, upon transition crossing, and at top energy. Transverse emittance growth, fast instabilities, and beam loss also occur upon transition crossing. Mitigation measures are implementedboth to reduce the productionof electron cloud and to control the beam stability.