Off-energy injection of Aladdin
Injection of the Aladdin 800-MeV electron storage ring is performed at a low ring energy of 108 MeV, where the stacking time period of 0.8 s is much smaller than the radiation damping time. Electrons are injected from inside the ring at a location where the horizontal dispersion is large, using an injected beam whose energy is 0.7 MeV lower than the equilibrium energy of the storage ring. We consider the initial horizontal offset of each injected electron to be the sum of an energy (“synchrotron”) oscillation and a betatron oscillation, and assume that the oscillations of different electrons decohere in the stacking time period. This model correctly predicts the successful stacking for off-energy injection at a location with large horizontal dispersion, and the poor stacking that occurs when injecting into a lattice whose horizontal dispersion is small at the injection location. The model also predicts that the maximum stacked current may be increased by nearly a factor of three if a 200-MeV linac is used for injection.