Used PEP-II 476 MHz Cavities for MEIC Collider Rings The Number of Cavities 36 Shunt Impedance () 7 MW (V2/P) Q0 31000 Coupler Beta 3.5 ~ 4.0 Maximum Vgap 1 MV Maximum Pfwd per Cavity 400 kW The Number of Klystrons 15 Strategy: Split cavities and klystrons in two rings with different cavity/Klystron ratio; Build a couple of new cavities if necessary upfront; Build new SC cavities in the future to gradually replace PEP-II cavities Option 1: 952MHz SC cavities in both rings Option 2: 476MHz SC cavities in e-ring, use PEP-II klystrons; 952MHz in i-ring with new klystrons

Top energy beam current (A) RF stepping up options CMS Energy (GeV) Ring Energy (GeV) Cavity technology Cav Num Cav Pfwd (kW) Total cavity Heat Total Pfwd (MW) Top energy beam current (A) Cavity gradient MV/m 37 e 6.95 476 NC 12 393.6 1.1 MW 4.7 1.1 2.5 ion 50 24 118 877kW 2.8 0.5 2.4 61 9.3 30 428 2.7 MW 12.8 0.95 100 952 SC 4K 83 460W 1 10 69? 18? 476 SC 4K 12? 69 128 16 77.6 571W 1.24 9.7 78.4 422 686W 0.341 7.2

476 MHz Cavities in Collider Rings for Bunch Length of 12 mm (GeV) I (A) Vgap (MV) Pforward (kW) Pcavity (kW) Cavity Number b Klystron Number Note e Ring 9.8 0.9 0.78 418 87.5 36 3.8 18 9.3 0.946 0.79 428 90.1 30 15 8.7 1.0 0.80 433 92.0 24 12 6.95 1.1 394 89.6 6 5.0 1.2 0.69 280 67.4 5 3 Ion Ring 29 0.5 128 88 3.5 2 125 86 16 50 0.76 118 82 100 129 89 48

All SC cavities in 100GeV Ion Ring 𝑑𝑉 𝑑𝑡 =𝑉∙ 𝜔 𝑅𝐹 =1.1∙ 10 17 𝑉/𝑠 𝑃 𝑓𝑤𝑑 ∝1/𝑓 for SC cav, same Y Cav Num Pfwd (kW) Total Pfwd (MW) Coupling beta Total cavity heat Cavity gradient MV/m Tuning angle (deg) Loading factor Y 476 MHz 16 125 2.0 1.60e4 499W 7.5 -67.1 2.37 12 166 1.20e4 665W 10 748.5 MHz 106 1.27 0.975e4 521W 952 MHz 83 1.0 0.87e4 460W 476 warm 48 129 6.2 3.5 4.2MW 2.5 -44.6 0.99

All SC cavities in e Ring @12GeV dY Common parameters: Cavity number = 24 Bunch length = 12 mm Operation Energy = 12 GeV Beam current = 0.341 A Cav Num Pfwd (kW) Prefl (kW) Cavity gradient MV/m Total cavity heat dY 476 MHz 24 421.9 5.21 7.2 686 W 0.25 748.5 MHz 419.46 2.76 8.6 768 W 0.233 952 MHz 9.844 887 W