The Proposed Conversion of CESR to an ILC Damping Ring Test Facility M. Palmer, R. Helms, D. Rubin, D. Sagan, J. Urban, M. Ehrlichman Abstract: In 2008 the Cornell Electron Storage Ring (CESR) will end nearly three decades of providing electron-positron collisions for the CLEO experiment. At that time it will be possible to reconfigure CESR as a damping ring test facility, CesrTF, for the International Linear Collider project. With its 12 damping wigglers, CesrTF will offer horizontal emittance in the few nanometer range and, ideally, vertical emittances approaching those specified for the ILC damping rings. An important feature of the CesrTF concept is the ability to operate with positrons or electrons. Positron operation will allow detailed testing of electron cloud issues critical for the operation of the ILC positron damping rings. Other key features include operation with wigglers that meet or exceed all ILC damping ring requirements, the ability to operate from 1.5 to 5.5 GeV beam energies, and the provision of a large insertion region for testing damping ring hardware. We discuss the CesrTF machine parameters, critical conversion issues, and experimental reach for damping ring studies. CesrTF Baseline Lattice CesrTF Conversion Dynamic Aperture bx North IR with Wigglers (Top View) Lattice design carried out with 6 wigglers in North IR and 6 wigglers in the CESR arcs. Zero dispersion regions created for all wigglers. by ~18 m Frequency Map Analysis Color Scale: Points plotted at ½ damping time Tunes calculated for 1st half and 2nd half of damping time South IR with RF Cavities for Short Bunch Operation (Top View) Wiggler Locations hx Move 6 wigglers to North IR Add cryogenic support Add electron cloud diagnostics Space for insertion devices in South IR Ample cryogenics support SCRF cavities for short bunch length operation Instrumentation (eg, possible laserwire installation) Could support an extraction line Upgrade feedback system for 4 ns spaced bunches Upgrade beam instrumentation Ultra-low emittance measurement CLEO North IR South IR 14W 15W 14E 15E 19E 19W Wiggler Moves Target ey~ 5 – 10 pm Parameter Value E 2.0 GeV Nwiggler 12 Bmax 2.1 T ex 2.25 nm Qx 14.59 Qy 9.63 Qz 0.098 sE/E 8.6 x 10-4 tx,y 47 ms sz 6.8 mm ap 6.4 x 10-3 Tune Scans to Determine Working Point Intrabeam Scattering (Preliminary) Low Emittance Operation Nominal CESR Magnet Alignment Resolutions Equilibrium Emittance with IBS for Baseline Lattice Calculation assumes vertical emittance is dominantly due to emittance coupling. ex grows by factor of ~3 from zero current to ILC bunch current Nominal Values Misalignment Nominal Value Quadrupole, Bend and Wiggler Offsets 150 mm Sextupole Offsets 300 mm Quadrupole, Bend, Wiggler and Sextupole Rotations 100 mrad Example Vertical Emittance Sensitivities IBS growth rates scale as 1/g4 a increase energy Increases zero current emittance Decreases sensitivity to IBS Can also lengthen bunch Explore 2.5 GeV lattice with 9 mm bunch as potential configuration for low emittance studies at the ILC bunch current (eg, electron cloud studies) Dominant Sensitivity Correction Algorithm Randomly misalign elements using multiple seeds Orbit correction followed by dispersion correction using steering and skew quadrupole correctors Include effects of BPM errors Equilibrium Emittance for 2.5 GeV Lattice and 9mm Bunch Length ex grows by a factor of < 1.6 from zero current to ILC bunch current. Zero current ex ~2.85 nm. . Correction Type Average Value 95% Limit Orbit Only 10.2 pm 21.4 pm Orbit+Dispersion 3.9 pm 8.2 pm CESR-c/CLEO-c program ends on March 31, 2008 7-9 month conversion followed by commissioning Available for ILC DR R&D in early 2009 Operating Schedule Approximately 110 running days/year in 2 periods Interleaved with CHESS X-ray running Significant downtime at each transition for installation of prototypes and other hardware Minimum of 3 years of operation as a test facility Conclusion: Simulations indicate that CesrTF can be operated in a regime that is useful for a range of damping ring studies. In particular, CesrTF will have the ability to study physics issues associated with the damping ring wigglers and validate the final design of the ILC wigglers and vacuum chamber. The machine will be able to directly explore the impact of the electron cloud on the emittance. Due to the modest scope of the conversion, CesrTF offers an efficient route towards exploring key areas of ILC damping ring physics and technology on a timescale consistent with the start of ILC construction. Conversion and Operations Plan