Systematic study on the static Robinson instability in an electron storage ring

The static Robinson instability and associated coherent synchrotron frequencies were systematically studied at the Photon Factory (PF) 2.5-GeV storage ring at KEK. Under machine parameters close to an anticipated Robinson limit, we observed beam dumps at which the beam and related signals were recorded. The evolution of the beam phase and the threshold condition at the beam dumps were consistent with theoretical values calculated based on the uniformly filled point-bunch model. However, we found remarkable discrepancies from theoretical predictions with additional coherent-frequency measurements. Under conditions close to the Robinson limit, we observed an unpredicted sharp peak at a frequency of approximately 5.2 kHz, together with discrepancies in both the frequency and damping rate of the coherent oscillation. These results indicate the importance of further experimental and theoretical studies on the static Robinson instability.

Automated summary

The static Robinson instability and associated coherent synchrotron frequencies were investigated at the Photon Factory (PF) 2.5-GeV storage ring at KEK. Experimental observations showed consistent results with theoretical predictions based on the uniformly filled point-bunch model, but discrepancies were found when additional coherent-frequency measurements were taken. An unexpected sharp peak at approximately 5.2 kHz was observed under conditions close to the Robinson limit, along with deviations in both the frequency and damping rate of the coherent oscillation. These findings emphasize the need for further experimental and theoretical studies on the static Robinson instability.