M. Hosaka, S. Koda, M. Katoh, J. Yamazaki and H. Hama(*)
UVSOR facility, Institute for Molecular Science, (*)Laboratory of Nuclear Science, Tohoku University
We are studying the longitudinal dynamics of electron beam in a storage ring FEL. The interaction between the laser light and the electrons causes enhancement of the energy spread of the electron beam, which is known as `bunch-heating'. The circulating electron bunch also interacts with the impedance of the environment such as the vacuum chamber. Combined effect of these processes is expected to lead to not only variation of the electron distribution in the bunch but also a phase shift of the bunch relative to the accelerating field of the RF-cavity. On the UVSOR storage ring, we have developed a technique to detect a phase of the electron bunch precisely using the higher harmonics of the revolution frequency and measured the phase shift under various conditions of the FEL lasing. Preliminary results show a large phase shift, which is probably due to a strong frequency dependence of the resistive impedance. Detailed analysis is going to be shown at the conference.
