P LANS FOR UTILIZING THE CORNELL ELECTRON STORAGE RING AS A TEST ACCELERATOR FOR ILC DAMPING RING RESEARCH AND DEVELOPMENT M. A. Palmer, † J. Alexander, M. Ehrlichman, D. Hartill, R. Helms, D. Rice, D. Rubin, D. Sagan, L. Sch¨ achter, J. Shanks, M. Tigner and J. Urban ‡ CLASSE, Cornell University, Ithaca, NY 14853-8001 Abstract Beginning in April 2008, we propose to employ the Cor- nell Electron Storage Ring (CESR) in a program of re- search and development for the International Linear Col- lider (ILC) Damping Rings (DR). This paper provides an update on the conceptual design issues for the CESR re- conﬁguration and details of the experimental program that will follow. INTRODUCTION On March 31, 2008 CESR will conclude nearly three decades of operations as an electron-positron collider for the CLEO experiment. At that time it will be possi- ble to reconﬁgure CESR as a test accelerator (CesrTA) for ILC damping rings R&D [1]. As the world’s only operating wiggler-dominated storage ring, CESR offers a unique facility with which to investigate beam physics is- sues and instrumentation critical to the design and opera- tion of the ILC damping rings. With its twelve damping wigglers, CesrTA will operate with horizontal emittances in the nanometer range and a vertical emittance and bunch spacing approaching those speciﬁed for the ILC damping rings. Furthermore, the CESR-c damping wigglers are the technology choice speciﬁed by the ILC Reference Design Report [2]. A core component of the CesrTA research pro- gram will be to study the electron cloud (EC) effect in the damping wigglers as well as in other machine components, and techniques to suppress it – a critical ILC design is- sue. An instrumented vacuum section with wiggler, bend, quadrupole and drift regions will be used for these studies. The measurements from these studies will be used to test the simulations of the EC effect. The changes required to make CESR available as a test accelerator are modest so that research results will be available in time for the ILC Engineering Design Report (EDR) in 2010. An important feature of the CesrTA concept is the abil- ity to operate with positrons or electrons. Positron opera- tion will allow detailed testing of EC issues critical for the operation of the ILC positron DR. By alternating operation between electron and positron beams, we will be able to carefully characterize and distinguish various species de- pendent and independent effects, including the EC effect and ion effects, in a single ring. Other key features of the CesrTA plan include operation with wigglers that meet or * Work supported by the U.S. National Science Foundation † map36@cornell.edu ‡ Now at Princeton Consultants Inc., Princeton, NJ exceed all ILC DR requirements, the capability to oper- ate with beam energies from 1.5 to 5.5 GeV. The ring will serve as a test bed for developing low emittance tuning al- gorithms and instrumentation and will provide a large in- sertion region for testing DR hardware. CESR RECONFIGURATION In order to obtain the smallest possible beam emittance, the CESR-c wigglers need to be located in regions with zero dispersion. CESR has two 18 m long interaction re- gions (IR) that meet this criterion. Figure 1 shows the present location of the CESR-c wigglers and the straight sections in the ring that occur in each of L0-L5. L0 is the South IR with the CLEO detector while L3 is the North IR, the location of the former CUSB detector. The CesrTA conversion will move six of the twelve wigglers, which are presently located in the arcs of the machine, to the South IR (L0). The wigglers located in the L1 and L5 straights will remain in place and zero dispersion regions will be created in the local optics at those places. Two spare wig- glers will be used to implement possible solutions for the vacuum chamber design to limit the buildup of the electron cloud. These modiﬁed wigglers will then be substituted for one or more of the wigglers in the South IR. This conﬁgu- ration of the wigglers will leave the North IR (L3) available for insertion devices, such as specialized beam instrumen- tation, and potential prototype damping ring hardware test- ing. The core modiﬁcations to CESR needed to enable the CesrTA program are: 1) relocation of the CESR-c damp- ing wigglers to regions with zero dispersion; 2) removal of the CLEO solenoid compensation elements and the ﬁ- nal focus quadrupoles in the South IR; 3) installation of local diagnostics for measuring EC densities, particularly in and around the dipole, quadrupole and wiggler magnets; 4) instrumentation upgrades to help obtain and measure ul- tra low emittance beams; and 5) improvements to CESR alignment and survey capabilities to provide the precision alignment required for ultra low emittance operation. Base- line parameters for a reconﬁgured machine operating at 2.0 GeV are shown in Table 1. ILC DAMPING RINGS R&D ISSUES A number of critical R&D items have been identiﬁed by the ILC DR group as important research priorities for the next few years [3]. The CesrTA research program will be MOOAKI01 Proceedings of PAC07, Albuquerque, New Mexico, USA 03 Linear Colliders, Lepton Accelerators and New Acceleration Techniques 42 A10 Damping Rings 1-4244-0917-9/07/$25.00 c 2007 IEEE