Update on MEIC Ion Polarization Work A.M. Kondratenko, M.A. Kondratenko, and Yu.N. Filatov presented by V.S. Morozov MEIC Weekly R&D Meeting July 16, 2015 F. Lin

Racetrack Booster Motivation to consider racetrack booster Shorter circumference better for space charge Lower cost

Ring Length Field integral of arc dipoles p, GeV/c , grad /π,% Racetrack Figure-8 BL, Tm Ldip, m 9 75 42 188 63 267 89

Spin Resonances in Racetrack About 80 resonances for protons Siberian snake (solenoidal, ~35 Tm, ~10 m long) With proper choice of tunes, 2 resonances for deuterons  individual crossing

Polarized Deuterons Snake not practical (~100 Tm, ~35 m long) Resonance crossing Characteristic ramp time giving full depolarization For Taccel = 0.01 T *, resonance w is crossed fast with 1% depolarization For Taccel = 100 T *, resonance w is crossed adiabatically with 1% depolarization For typical booster parameters  fast crossing requires ~2 s ramp time (demonstrated in Nuclotron)  at slower rates, easier to use figure-8

Conclusions & Outlook Siberian snake eliminates proton depolarization in a racetrack booster Deuteron polarization can be preserved with acceleration time of ~1 s Has the additional benefit of faster booster cycle: faster fill of the collider ring, long beam lifetime in the booster not needed, etc. Would be good to have a test racetrack lattice to evaluate resonances extraction RF cavity Crossing angle: 75 deg. Ekin = 285 MeV – 8 GeV injection