First observation of simultaneous alpha buckets in a quasi-isochronous storage ring

We present the first experimental evidence confirming the theoretical predi ctions of alpha buckets in an electron storage ring. By controlling both th e first- and second-order momentum compaction factors. we succeeded in stor ing electrons simultaneously in a pair of alpha buckets or in either bucket alone. The two electron bunches are separated in energy by slightly less t han 1% and thr energy is unable over a narrow range. The energy difference was directly measured using synchrotron light from an undulator. Simultaneo us two-color light beams from an undulator were generated. By changing thc rf voltage, we were able to vary the normally fixed longitudinal bunch sepa ration.