Status and plans for crab crossing studies at JLEIC Salvador Sosa, ODU Vasiliy Morozov, JLab

Outline Impact of beam crossing angle on luminosity and necessity of crab crossing Outline of crab crossing schemes Preliminary self-consistent set of crab crossing parameters Start crab crossing simulations Future Plans

Luminosity and need for Crabbing

Luminosity Reduction Factor Crossing beam parameters θc 50 mrad σz 9.08 mm σx 18.04 µm φ 12.5 rad  

Ion Collider Ring Figure-8 ring with a circumference of 2153.9 m Two 261.7 arcs connected by two straights crossing at 81.7 Vertical doglegs to be added R = 155.5 m Arc, 261.7 IP disp. supp./ geom. match #3 geom. match #1 geom. match #2 det. elem. disp. supp. norm.+ SRF tune tromb.+ match beam exp./ elec. cool. ions 81.7 future 2nd IP Polarimeter IP crossing angle of 50 mrad Luminosity requirement: 7.5x1033 cm-2s-1

Detector Region Layout e- crab cavities ion crab cavities IP e- Compton polarimetry forward ion detection ions forward e- detection dispersion suppressor/ geometric match spectrometers Forward hadron spectrometer low-Q2 electron detection and Compton polarimeter p (top view in GEANT4) e ZDC

Baseline Ion IR Optics IR design features Modular design Based on triplet Final Focusing Blocks (FFB) Asymmetric design to satisfy detector requirements and reduce chromaticity Spectrometer dipoles before and after downstream FFB, second focus downstream of IP No dispersion at IP, achromatic optics downstream of IP detector elements match/ beam compression IP match/ beam expansion geom. match/ disp. suppression FFB FFB ions Secondary focus with large Dx for improved momentum resolution

Location of crab cavities Crab Crossing Effective head-on bunch collisions restored with 50 mrad crossing angle Local crab scheme Two cavities are placed at (2n+1)/2 phase advance relative to IP Optimal x at locations of crab cavities for minimizing the required kicking voltage Deflective crabbing using transverse electric field of SRF cavities (as at KEK-B) Design and analysis completed Prototype fabricated and characterized Final testing with promising results Location of crab cavities π/2 3π/2 Multipole Tailoring Beam Dynamics Studies

Crab crossing Design Parameters S. Abeyratne et al, MEIC Design Summary, arXiv:1504.07961 Parameter Unit Electron Proton Energy GeV 10 100 Bunch frequency MHz 952.6 Crossing angle mrad 50 Betatron function @ IP cm Betatron function @ crab cavity m 200 750 | 400 Integrated kicking voltage MV 2.8 14.47 | 19.81   Deflecting (kicking) voltage amplitude:

Bunch at IP with and w/o crabbing Bunched Beam parameters N particles 10,000 εnx σs 1 cm Gaussian distribution 3 - sigma

Crab crossing plan Optimize the crabbing system for best beam stability and minimum emittance impact Study effects of and specify tolerances on crab cavity errors such as misalignment, amplitude and phase instability Study and specify tolerances on cavity multipole components by estimating impact on the ring’s dynamic aperture Specify high-order mode requirements Specify requirement on the beam parameters such as maximum bunch length Evaluate and optimize impedance of the crab cavities Complete beam dynamics simulation using an optimized field map satisfying the determined requirements