TUNE MEASUREMENT OF SRRC BOOSTER DURING RAMPING

The setup for tune measurement of Synchrotron Radiation Research Center (SRRC) booster and its performance are described in this report. Tune drift during ramping was observed in routine operation. The fractional tune drift can be as large as 0.2. In some of the cases, beam capture at injection and its acceleration was severely degraded. In order to improve this situation, a measurement system was set up to monitor tune shift during ramping. Tune information was obtained by using FFT conversion of turn by turn beam position signals. Besides, tracking errors among focusing/defocusing quadrupoles and dipole were monitored with precision magnetic current meters. Their ratio varied during ramping was correlated to the tune shift mentioned above. With the help of these two monitoring tools, the working tunes were optimized to get more efficient operation. 1 INTRODUCTION In order to provide 1.5 GeV electron beam for the SRRC storage ring, electrons have to be generated and accelerated. The electron is first emitted by an electron gun and accelerated up to 50 MeV through an rf linac. This 50 MeV electron beams is then injected into a booster synchrotron in which the electron beam energy is raised up to 1.5 GeV. Finally, the electron beam is extracted from the booster and fed into the storage ring. It happened that the electron beams were lost during injection and energy ramping after some major failure of the power supplies systems and their components. Usually, maneuvering the booster lattice to appropriate working points can solve the problem. Recently, a tune monitoring system was installed into the booster control system. It provides the capability of monitoring the booster tunes, νx and νy , during ramping. By comparing the measured tune drift during ramping with the observed tracking errors among magnet families, correlation between these two features can be concluded. The experimental setup and preliminary test result of this tune monitoring system is described in this report.