1. 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
April 9, 2015
F. Lin

2. Booster Additional arc bending angle in the figure-8 booster of 150
Additional integrated dipole field BL = B = 69.4 Tm (?)
Extra space for quadrupoles, etc.
Racetrack booster
Should not be a problem for deuterons
Requires ~10 m long Siberian snake with ~35 Tm longitudinal field integral
Snake field must ramp with energy
Additional quadrupoles for optical compensation: focusing, coupling, etc.
Shorter circumference is better for space charge

3. Deuteron Polarization in Collider Ring
Estimate of intrinsic resonance strengths
Characteristic field ramp time corresponding to full depolarization after crossing of an intrinsic resonance
For Taccel = 0.01 T *, an intrinsic resonance is crossed fast with 1% depolarization
For Taccel = 100 T *, an intrinsic resonance is crossed adiabatically with 1% depolarization
For intrinsic resonances, adiabatic depolarization drops off as a power law rather than exponentially
Larc, m
Lstr, m
Lring, m
Figure 8
2710
2360
2140
Racetrack
2490 (?)
1700

4. Deuteron Polarization in Collider Ring
The characteristic acceleration time
Resonance jumps can be used if the ramp time is of the order of T *. Then weaker resonances are crossed quickly. If the ramp is slow then the weaker resonances cause complete depolarization. With a ramp of the order of a minute, it is not practical to preserve deuteron polarization in a racetrack. It can only be done in a figure-8 ring.
Dubna magnet technology, in principle, allows 1 s ramp time, which may allow preserving deuteron polarization in a racetrack. However, this requires lattice optimization and accounting for fine effects such as synchrotron sideband spin resonances.
Preservation of the polarization does not guarantee polarization lifetime. One hour polarization lifetime requires detuning from all spin resonances with strengths greater than 10-6 by an amount greater than the spin tune spread. This requires careful analysis.

5. Proton Polarization in Collider Ring
Compared to a racetrack, figure 8 with 81.7 crossing angle requires additional integrated arc dipole field of ~950 Tm (?)
Running a racetrack in a spin transparent mode requires two identical Siberian snakes inserted in the opposite straights
Required field integral of helical snakes is about 50 Tm (?)
One has to consider a betatron tune shift of up to ~0.05 at low energies
Requires additional quadrupole compensation