  The choice of a figure 8 shape for the booster and collider rings of MEIC
opens wide possibilities for preservation of the ion polarization during beam
acceleration as well as for control of the polarization at the collider's
interaction points. As in the case of accelerators with Siberian snakes, the
spin tune is energy independent but is equal to zero instead of one half. The
figure-8 topology eliminates the effect of arcs on the spin motion. There
appears a unique opportunity to control the polarization of any particle
species including deuterons, using longitudinal fields of small integrated
strength (weak solenoids). Contrary to existing schemes, using weak solenoids
in figure-8 colliders, one can control the polarization at the interaction
points without essentially any effect on the beam's orbital characteristics. A
universal scheme for control of the polarization using weak solenoids provides
an elegant solution to the problem of ion acceleration completely eliminating
resonant beam depolarization. It allows one to easily adjust the polarization
in any direction at any orbital location, which becomes necessary when
transferring the beam from one ring into another or when measuring the
polarization by polarimeters. It also allows for an easy manipulation of the
spin direction at an interaction point during an experiment. The latter feature
allows one to set up a spin-flipping system with a spin reversal time of less
than a second. By compensating the coherent part of the zero-integer spin
resonance strength, which arises due to errors in alignment of the magnetic
element of the lattice, one can reduce the field integrals of the control
solenoids by a few orders of magnitude.
