CESR Low Emittance Upgrade with Combined Function Bends

The Cornell Electron Storage Ring is the laboratory for the CESR Test Accelerator damping ring R&D program, and the source of x-rays for the Cornell High Energy Synchrotron Source. A peculiarity of the layout of the storage ring is that horizontal emittance is generated predominantly by the strong bends in the sextant of the ring that was designed with a long straight to accommodate the interaction region required when the machine operated as an electron-positron collider. By reconfiguring that single sextant (L0) we reduce the emittance by 50% to 25 nm-rad at 5.3 GeV for x-ray production and with damping wigglers to 1.5 nm-rad at 2.1 GeV for investigations of low emittance phenomena. The 35 m radius of curvature, 3.2 meter long dipoles are refitted as combined function (vertically focusing) magnets to create simple achromats. The connecting zero dispersion straights can accommodate as many as six, 3 meter long undulators, in addition to six superconducting damping wigglers. By virtue of reducing horizontal emittance and energy spread at 2.1 GeV, the reconfiguration enhances the sensitivity of CESR to the emittance diluting effects that are the subject of the CesrTA study. At the same time, operation as a light source is significantly improved with lower emittance, and as many as six new undulator beam lines. The reconfigured hard bend region can be the basis of a global upgrade of the storage ring. By extending the conversion of single function to combined function magnets to all of the ring dipoles, we reduce the horizontal emittance at 5 GeV (for x-ray operation) to ∼ 1nm-rad and at 2 GeV (for damping ring studies) to less than 80 pm-rad, well into the parameter space of the worlds most brilliant x-ray sources and ambitious positron sources.