1. Progress Update on the Electron Polarization Study in the JLEIC
Fanglei Lin
JLEIC R&D Meeting, March 2, 2017
F. Lin

2. Current Status and Working Plan
Electron polarization lifetime at 5 GeV was calculated using analytical code SLICK and Monte-Carlo simulation code SLICKTRACK, for the baseline JLEIC electron collider ring design.
Polarization lifetimes at other energies are simply scaled at this moment, should and will be verified once the lattice design is finalized.
Spin tune scans with quadrupole vertical misalignment and dipole role were performed at 5GeV JLEIC electron collider ring.
Simulation shows no synchrotron sideband resonances in the figure-8 shape electron collider ring.
Spin-orbit depolarization time reduces by a factor of 2.6 in the reduced-emittance ring optics (30% emittance reduction coming from optimization of matching and spin rotator sections in the baseline design using PEP-II magnets).
Working on spin tracking using ZGOUBI for benchmarking.
Working Plan:
Continue spin tracking using ZGOUBI
Study the beam-beam effect on the polarization
Study the crab crossing effect on the polarization
Develop spin matching to extend the polarization lifetime
See Vasiliy’s talk about collaboration with A. Kondratenko’s team

3. Back Up

4. Spin Tune Scan
SLICK/SLICKTRACK allows one to insert a zero length spin tuning magnet to move the spin tune away from zero. Such magnet in the code only rotates the spin, leaving the orbit intact.
Longitudinal field spin tuning solenoid in one straight where the polarization is longitudinal
Only moves the spin tune away from zero
Does not change the spin direction
Breaks the current spin matching condition in the straight IP
Spin Rotator e-
Magnetic field
Polarization
Spin tuning solenoid

5. Spin Tune 5 GeV
Quadrupole vertical misalignment with a rms value of 0.2mm and dipole role with a rms value of 0.2 mrad. The orbit is corrected with correctors around the ring.
First order spin resonance occurs when
500 electrons in the Monte-Carlo simulation
Optimum Spin Tune
Nasty, nasty sidebands !
Figure-8 MEIC collider ring has no synchrotron sideband resonances !

6. Baseline Electron Ring
Circumference of m = 2 x m arcs + 2 x straights
Chromaticities: (H,V) = (-149, -123)
Figure-8 crossing angle 81.7
Electron collider ring w/ major machine components e-
R=155m RF
Spin rotator
CCB
Arc, 261.7
81.7
Forward e- detection IP
Tune trombone & Straight FODOs
Future 2nd IP
Regular arc FODO cell
Spin rotator
Matching section
Dipole set
2nd sol. + decoupling quads
1st sol. + decoupling quads

7. Reduced-Emittance Electron Ring
Circumference of m = 2 x m arcs + 2 x straights
Chromaticities: (H,V) = (-138, -119)
Figure-8 crossing angle 81.7
Regular arc FODO cell
Spin rotator
Dipole set
2nd sol. + decoupling quads
1st sol. + decoupling quads

8. Spin Tune 5 GeV
Quadrupole vertical misalignment with a rms value of 0.2mm and dipole role with a rms value of 0.2 mrad. The orbit is corrected with correctors around the ring.
First order spin resonance occurs when
500 electrons in the Monte-Carlo simulation
Optimum Spin Tune
Optimum Spin Tune
Spin-orbit depolarization time reduces by a factor of 2.6 in the reduced-emittance ring optics

9. Solenoid Strength Spin tuning solenoid strengths in spin tune scans
Optimum Spin Tune
For the optimum spin tune of where the polarization lifetime reaches 8 hours, the required integral of spin tuning solenoid field is ~3 Tm.
The stronger the solenoid field is, the larger the spin tune is. But the strong solenoid field breaks the spin matching badly and leaves a short polarization lifetime.