Beam Synchronization in MEIC: The Problem, Scale and Prospect Protons and ions in the medium energy range of MEIC are not fully relativistic yet The proton/ion revolution time in the ion collider ring depends on the beam energy The electron revolution time is effectively a constant Electrons and ions will not collide at interaction points after one revolution of their collider rings Path length adjustment and change of number of bunches for at least one collider ring/beam Scale MEIC collision energy range: 30 to 100 GeV for protons, 12 to 40 GeV/u for heavy ions (possible staging scenario 18 to 40 GeV/u for heavy ions) Required path-length adjustment: 5.55 m (100 to 12 GeV) or 2.54 m (100 to 18 GeV) (MEIC collider ring circumference is assumed 2142 m) If change of bunches is allowed in the ion ring, then we need to add up to 8 (4) new bunches. Path length adjustment range is now reduced to one bunch spacing, 63 cm @ 476 MHz RF Prospect Unprecedented, due to requirement of the EIC program (low energy, large energy range) (Previous colliders: lepton colliders and LHC – ultra-relativistic; HERA – one energy; Tevatron and RHIC -- symmetric Two orders of magnitude larger than what are required for other colliders

Discussion Topics Conventional Schemes Harmonic Numbers Where we do path length change: ion ring vs. electron ring Harmonic Numbers Non-integer harmonic number Different RF frequency (476 MHz vs. 9520 MHz) “Change of Gear” Dynamic effect Can we avoid it? Scanning Synchronization Scheme Technology Issues Moving magnets from engineering point view Related topics Gaps

Backup Plan: Harmonic Change w/o Gear Change Key points Allow harmonic number change in the ion ring Change the harmonic number in the electron ring to match the harmonic number in the ion ring Change electron ring path length to accommodate additional electron bunches Have multiple by-pass beam lines (order of 100 to 200 m) to absorb large path length change Have two or four chicane-on-arc to adjust +/- half bunch spacing (for one IP) for covering energies between harmonic energies. Why change harmonic numbers in the ion ring? Making the RF frequency change too large Why change harmonic numbers in the electron ring? Have the same bunch numbers in two ring