Studies of transverse single-bunch instabilities in booster synchrotrons

The capability of providing full-charge bunches has become an important requirement for quite a few boosters used in ultralow-emittance storage rings based synchrotron light sources. The transverse single-bunch instabilities may limit the single-bunch charge in these type of boosters. The relatively weak synchrotron radiation damping makes the bunch more unstable at the injection energy than at the extraction energy. Therefore, studies of the transverse single-bunch instabilities are carried out first at the injection energy, with the chromaticity varied, to understand how the threshold changes accordingly. Our studies show that the single-bunch threshold current tends to drop when the chromaticity becomes nonzero at the injection energy of the used booster lattice. The corresponding simulation results are presented and analyzed. Furthermore, the transverse single-bunch instabilities during the energy ramping process are also studied.