Longitudinal acceptance measurement at an electron storage ring

The longitudinal acceptance of the BESSY II storage ring has been measured. To our knowledge, such a measurement has never been performed in electron storage rings. The study is also motivated by the fact that for future diffraction limited light sources a couple of longitudinal injection schemes were proposed recently. In these injection schemes, the energy and/or timing of the injection beam is shifted, resulting in a large synchrotron oscillation amplitude of the injected beam. It is, therefore, of importance to reveal whether we can evaluate the longitudinal acceptance precisely when we design a storage ring with a longitudinal injection scheme. The experimental results showed a good agreement to the acceptance evaluated through the accelerator model, including the special feature arising from the synchrotron radiation. We also found that, as a by-product, the bunch length of the injected beam can be obtained from the acceptance measurement data. The result is in good agreement with the design value of the injector booster synchrotron.