MEASUREMENT OF THE BUNCH LENGTH ON THE UVSOR STORAGE RING

We have measured the bunch length in single-bunch operation of the UVSOR (Ultraviolet Synchrotron Orbital Radiation) storage ring in a beam current region from 0.1 to 70 mA at energies ranging from 500 to 750 MeV. The momentum compaction factor of the present operation point is determined experimentally from the bunch length and the synchrotron oscillation frequency measured simultaneously at a low beam current. The bunch length increases gradually as the beam current increases, and bunch lengthening is larger when the beam energy is lower. This behavior of bunch lengthening agrees well with a prediction of the potential-well distortion theory. Based on the theory, the effective longitudinal coupling impedance is estimated as a function of bunch length.