Measurement of injection energy mismatch in circular accelerators using rf capture efficiency observations

A general method for measuring the energy mismatch between a storage ring and its injector is presented. The energy mismatch is defined as the difference between the injector energy and the synchronous energy of the storage ring. Observations of the rf capture of the injected beam when the energy acceptance or synchronous energy are varied yield the energy mismatch. The energy acceptance and synchronous energy are easily varied by changing the rf accelerating voltage, the rf frequency, or both. As an example, measurements performed on the 1 GeV electron storage ring Aladdin show an energy mismatch of 0.666 MeV at the injection energy of 108 MeV. This agrees with theoretical predictions about injection stacking at a rate faster than the radiation damping rates.