Fast-stacking off-energy injection into the Aladdin electron storage ring

Injection into an electron storage ring may be performed at a low energy where the radiation damping time constant is several seconds. When the horizontal dispersion at the injection location is sufficiently large, injection may be enhanced by fast-stacking off-energy injection, in which the injection repetition period is much smaller than the radiation damping time and the energy of injected electrons differs from the ring energy.Assuming that betatron oscillations and synchrotron oscillations fully decohere within one injection repetition period, we obtain analytical formulas for the probability that an electron survives the injection process, the accumulation rate of stored ring current, and the maximum ring current. For 108-MeV injection into the Aladdin electron storage ring, the measured survival probability, accumulation rate, and injected beam energy agree with the formulas, while the maximum ring current is smaller than predicted because of trapped ions. The formulas and measurements confirm the benefit of fast-stacking off-energy injection.