1. Simulation Study For MEIC Electron Cooling He Zhang, Yuhong Zhang Thomas Jefferson National Accelerator Facility Abstract Electron cooling of the ion beams is one critical R&D to achieve high luminosities in JLab’s MEIC proposal. In the present MEIC design, a multi-staged cooling scheme is adapted, which includes DC electron cooling in the pre-booster and bunched electron cooling in the collider ring at both the injection energy and the collision energy. The high electron energy and current needed in the bunched electron cooling of MEIC is beyond the-state-of the-art. A concept of an ERL driven electron cooler with a circulator ring has been developed to meet these technical challenges. In this paper, we present simulation studies of electron cooling in MEIC. We also explore the MEIC luminosity performance if applying weak cooling (namely, with a reduced electron beam current) only or no cooling in the collider ring. Strong Cooling in Collider Ring Weak Cooling in Collider Ring Acknowledgement The authors want to say thanks to Ya Derbenev and V. Morozov at JLab, A. Fedotov at BNL, L. Mao at IMP in China, and A. Smirnov at JINR in Russia for beneficial discussions. Work supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE- AC05-06OR23177 and No. DE-AC02 -06CH11357. Introduction [1] The MEIC can deliver a luminosity above 10 34 cm -2 s -1 at a center-of-mass energy up to 65 GeV. It offers an electron energy up to 11 GeV, a proton energy up to 100 GeV, and corresponding energies per nucleon for heavy ions with the same magnetic rigidity. The conventional electron cooling is chosen to reduce or preserve the emittance of the MEIC ion beam. As shown in the following picture of MEIC Ion Complex, our multi-phase electron cooling strategy includes the following steps: 1.Low energy (3 GeV) DC cooling at the pre-booster 2.Cooling at the injection energy (25GeV) of the collider ring 3.Cooling at the top energy (up to 100GeV) of the collider ring Here we present simulation results for three different schemes (with the same DC cooling in pre-booster) 1.Strong cooling in collider ring (1.5A e - beam) 2.Weak cooling in collider ring (0.375 A e - beam) 3.No cooling in collider ring DC Cooling in Pre-Booster Luminosity Fig. 2 Cooling in the pre-booster ion bunch electron bunch circulator ring Cooling section solenoid Fast kicker SRF Linac dump injector No Cooling in Collider Ring ion bunch electron bunch circulator ring Cooling section solenoid Fast kicker SRF Linac dump injector Fig. 1 MEIC ion complex layout Electron Cooling Simulation using BETACOOL The following stages are simulated: 1. In prebooster, using DC electron beam to cool 3 GeV coasting proton beam 2. In ion collider ring, using Gaussian bunched electron beam to cool 25 GeV coasting proton beam for both strong cooling and weak cooling 3. In ion collider ring, using Gaussian bunched electron beam to cool 60/100 GeV Gaussian bunched proton beam for both strong cooling and weak cooling In all stages, we calculate the IBS effect and the electron cooling effect. In all stages, the IBS effects are calculated by Martini model, and the cooling effects are calculated by thin lens model. In the pre-booster, model beam method is used in dynamic simulation. In the collider ring, RMS dynamics method (single particle model) is used. [1] Science requirements and conceptual design for a polarized medium energy electron-ion collider at Jefferson Lab, Editors: Y. Zhang, J. Bisognano, August 10, 2012 Fig. 11 IBS induced emittance expansion (60GeV) Fig. 12 IBS induced emittance expansion (100GeV) Fig. 13 Luminosities of different schemes at 60 GeV Fig. 14 Luminosities of different schemes at 100 GeV E p, N p and l p means the kinetic energy, particle number and the bunch length of the proton beam. B is the longitudinal magnetic field inside the cooler. l c is the cooler length. I e and l e are current and bunch length of the electron beam. The fifth and sixth columns are the parameters for strong and weak cooling in the collider ring respectively.