Performance of the Cesr Superconducting Rf System and Future Plans*

As we have reported at the last SRF Workshop two years ago, staged transition of the Cornell Electron Storage Ring (CESR) RF System from normal conducting to superconducting was completed in September 1999 with installation of the fourth superconducting B-cell cavity [1]. Since that time the last cavity has been commissioned and RF system has operated stably providing CESR beams with up to 1.13 MW of RF power to support total beam current up to 800 mA. CESR is a symmetric energy ee collider operating in a bunch train mode with CLEO detector studying B meson decays at thte center of mass energy near the Υ(4S) resonance (≈5.3 GeV) [2]. At the same time CESR provides beams for experiments with synchrotron radiation (SR) at the Cornell High-Energy Synchrotron Source (CHESS). CHESS facility operates in a parasitic mode simultaneously with high-energy physics experiments at CLEO. The latest running period lasted nine months ending in June 2001. The emphasis was put on a steady running of the machine aiming to reach integrated luminosity of at least 10 fb. This goal was achieved by delivering of just over 11 fb. The typical total beam current at the start of the fill was 750 mA and typical RF power delivered to beam by one cavity was 280 kW. Beginning in the fall 2001 CESR will run at Υ resonances below Υ(4S), and during machine studies periods at J/Ψ resonances [3]. Eventually, after some hardware modification and upgrade, CESR will be able to operate over the energy range of 1.5 to 5.6 GeV with expected luminosity of 3×10 cms at 1.9 GeV. CLEO and CHESS will then operate in a time-sharing mode of operation. The CESR upgrade includes modification of the RF. Two more superconducting cavities will be added to provide higher total RF voltage for bunch shortening.