Orbit and spin tracking in a radial electric field
  I derive an expression for the spin decoherence rate for a smooth focusing electrostatic ring with a radial electric field. The answer contains some salutary lessons about spin decoherence calculations in electrostatic storage rings: the numerical tracking results disagreed with naive analytical calculations, but it was the tracking results which were correct, and more careful analytical calculations (canonical transformations) were required. 
S R Mane
physics.acc-ph