Collider Ring Optics & Related Issues Vasiliy Morozov for the JLab EIC Study Group

MEIC Layout Prebooster 0.2GeV/c  3-5 GeV/c protons Big booster 3-5GeV/c  up to 20 GeV/c protons 3 Figure-8 rings stacked vertically

Big Booster Acceleration of protons from 3-5 GeV/c to up to 20 GeV/c for injection into ion collider ring Big booster implementation options Separate warm ring in collider rings’ tunnel (current baseline) Using the electron ring Separate cold ring in the prebooster’s tunnel Big booster design considerations Avoid transition energy crossing Space charge  higher injection energy for larger ring Matching RF systems  debunch low-frequency beam and then rebunch it at higher frequency?

Ion Collider Ring Layout Geometrical matching of electron and ion rings Spin rotators in the electron ring Siberian snakes in the proton ring arcs Siberian snake Ion Ring Electron Ring Spin rotators

Modular Design Concept Design separately and incorporate/match into the ring Vertical chicanes for stacking the ion ring arcs on top of the electron ring Injection section Electron cooling section Siberian snakes Interaction region with horizontal crossing Section for local chromaticity compensation

Adjusting quad strengths Basic Ring Parameters Proton beam momentum GeV/c 60 Circumference m 1041.11 Arc’s net bend deg 240 Straights’ crossing angle Arc length 300.5 Arc average radius 71.74 Straight section length 220.06 Lattice basic cell FODO Arc / straight FODO cell length 9 / 6.16 Nominal phase advance per cell x / y 90 / 90 Number of arc / straight FODO cells 54 / 68 Dispersion suppression Adjusting quad strengths

Magnet Parameters Proton beam momentum GeV/c 60 Number of dipoles 108 Dipole length m 3 Bending radius 38.7 Bending angle deg 4.4 Bending field T 5.2 Number of quads 288 Quad length 0.5 Quad strength in arc / straight FODO cells T/m 130 / 195

Arc FODO Cell /2 betatron phase advance in both planes Magnet parameters for 60 GeV/c protons: Dipoles: length = 3 m bending radius = 38.7 m bending angle = 4.4 bending field = 5.2 T Quads: length = 0.5 m strength = 130 T/m

Dispersion Suppressor Quads in 3 FODO cells varied to suppress dispersion while keeping -functions from growing Maximum quad strength at 60 GeV/c = 148 T/m

Short Straight for Siberian Snake Symmetric quad arrangement Initial  values from the dispersion suppressor Quads varied to obtain x,y = 0 in the middle at limited max Maximum quad strength at 60 GeV/c = 130 T/m

Arc End with Dispersion Suppression Indicated quads varied to suppress dispersion with limitations on max and Dmax Maximum quad strength at 60 GeV/c = 212 T/m Varied quads Regular FODO To straight section

Complete Arc Length = 300.5 m, net bend = 240, average radius = 72 m

Straight FODO Cell /2 betatron phase advance in both planes Drift length chosen to close the ring’s geometry Quad strength at 60 GeV/c = 195 T/m

Arc to Straight Matching Section Four quads in two FODO cells adjusted to match ’s and ’s from arcs to straight’s standard FODO cell Maximum quad strength at 60 GeV/c = 222 T/m

Complete Figure-8 Ring Total length = 1041 m

Figure-8 Ring Layout 100 m

Summary of Optics Parameters Proton beam momentum GeV/c 60 Circumference m 1041.11 Arc’s net bend deg 240 Straights’ crossing angle Arc length 300.5 Straight section length 220.06 Maximum horizontal / vertical  functions 20.8 / 20.8 Maximum horizontal dispersion Dx 2.01 Horizontal / vertical betatron tunes x,y 33.(03) / 33. (16) Horizontal / vertical chromaticitiesx,y -43.31 / -43.01 Momentum compaction factor  4.7 10-3 Transition energy tr 14.58 Horizontal / vertical normalized emittance x,y µm rad 0.35 / 0.07 At 20 GeV/c injection: Maximum horizontal / vertical rms beam size x,y 15* horizontal / vertical beam stay clear mm 4 / 4 2 / 2 30 / 30