CESR status and plans

The CESR electron positron collider has been configured to operate with trains of closely spaced bunches that collide with a small horizontal crossing angle. The crossing angle scenario provides for an increase from seven to as many as 45 bunches per beam. Two pairs of electrostatic separators yield differential horizontal closed orbits for the electron and positron beams. The separators are powered antisymmetrically with respect to the two-fold symmetry of the storage ring. The bunches collide with a small horizontal angle of ±2.1 mrad, that serves to separate the counterrotating bunches at the parasitic crossing points adjacent to the IP. Nine trains, with temporal length of up to 56 ns can be accommodated. The storage ring has operated for high energy physics with trains of two bunches spaced 28 ns apart and reached peak luminosity of 3.3×10³² cm^-2 s^-1. The Phase II upgrade of the interaction region, now underway, will permit an increase in current to 300 mA per beam, and luminosity to 6×10³² cm^-2 s^-1. In Phase III of the CESR upgrade, scheduled for completion in 1995, the room temperature RF system will be replaced with single cell superconducting cavities. The single beam limit will increase to 500 mA, and the luminosity to 10³³ cm^-2 s^-1