CESR performance and upgrade status

The CESR electron-positron collider operates with nine trains of closely spaced bunches stored in each beam. During the Fall of 1998 the number of bunches in each of the trains was increased from three to four and the spacing of the bunches reduced from 28ns to 14ns. A beam current of 550mA was supported by two single cell superconducting cavities and two 5-cell copper cavities. We measured a peak luminosity of 8.3×10³² cm^-2 s^-1 and a beam-beam tune shift parameter of ξ_ν=0.05. The replacement of the remaining room temperature cavities with superconducting RF cavities in the next several months will provide the capability to store a total beam current of 1A. Because of the very low impedance of the superconducting RF we anticipate the longitudinal instability threshold to be in excess of 1A. And with an accelerating gradient of 10 MV/m, the bunch length in CESR can be decreased from the present value of 19 mm to 13 mm so that we can exploit a corresponding decrease in β*. The interaction region optics will be replaced in 2000 with a hybrid of permanent magnet quadrupole and superconducting quadrupoles. Magnet gradients and apertures are consistent with a vertical β of as small as 7mm