Measurements of transverse instabilities in the photon factory storage ring

In the Photon Factory electron storage ring (PF ring), transverse instabilities have been observed in multi-bunch operation mode. The instabilities can be suppressed by octupole magnets which produce amplitude dependent tune shifts. We have measured the response of the instabilities to the tune shifts with varying the field strengths of the octupole magnets to extend our knowledge on the instabilities. The thresholds of the instabilities were observed at a certain field strength, and they depended on the bunch filling pattern of the beam and the beam current per bunch. In addition, we have observed that the present behavior of the instabilities is clearly different from that before the reconstruction of the ring. (author)