CESR performance and upgrade status

The performance of the Cornell Electron Storage Ring (CESR) e+e- collider will be reviewed. CESR collides trains of closely spaced bunches at a small horizontal crossing angle. At present, CESR collides 36 bunches per beam at total currents up to 550 mA. A peak luminosity of 8.3 x 1032 cm-2 sec-1 has been achieved. A longitudinal beam instability due to higher-order-modes in CESR's normal conducting RF cavities has limited total beam currents. This current limitation has been addressed with wideband multibunch feedback and replacement of CESR's normal-conducting cavities with low-impedance single-cell superconducting cavities. The status of the longitudinal beam stability is described and experience with SRF in operation is discussed. Finally, plans are presented for a new interaction region optics (CESR Phase III) based on high-gradient superconducting quadrupoles which will allow a reduction in βv* from the present 19 mm to as low as 7 mm. The superconducting RF system will support a beam current of 1 A at a bunch length of 13 mm, giving a peak luminosity of 2 x 1033 cm-2 sec-1. (author)