A new purification method for single bunch operation at the Photon Factory storage ring

Recently, the requests for single bunch operation of the Photon Factory 2.5 GeV electron storage ring (PF-ring) have gradually increased and the requirements for the impurity, that is the rate of electrons in undesirable buckets to those in the main bunch, becomes severe. A purification method making use of the current dependence of the betatron tune has been applied up to present. However, after the reconstruction of the PF-ring toward low emittance optics, it requires a mastery skill to keep an impurity better than 10^-5 and moreover the transversal motion of the main bunch excited by the method could affect experiments of SR users. In order to overcome the situation and improve the purity, a new single-bunch purification method, that is essentially a “selective RF knock-out (RFKO)”, has been developed. The system worked stably during the users time and the typical impurity of 0.6×10^-7 was achieved. Schematic description of the selective RFKO is shown and related parameters of the PF-ring are shown