Vertical instability at IPNS RCS

S. Wang, F. R. Brumwell, J. C. Dooling, K. C. Harkay, R. Kustom, G. McMichael, M. E. Middendorf, A. Nassiri
2007 2007 IEEE Particle Accelerator Conference (PAC)  
The Rapid Cycling Synchrotron (RCS) of the Intense Pulsed Neutron Source (IPNS) at ANL accelerates > 3.0 × 10 12 protons from 50 MeV to 450 MeV with 30-Hz repetition frequency. During the acceleration cycle, the rf frequency varies from 2.21 MHz to 5.14 MHz. Presently, the beam current is limited by a vertical instability. By analyzing turn-by-turn beam position monitor (BPM) data, largeamplitude mode 0 and mode 1 vertical beam centroid oscillations were observed in the later part of the
more » ... part of the acceleration cycle. The oscillations start in the tail of the bunch, build up, and remain localized in the tail half of the bunch. This vertical instability was compared with a head-tail instability that was intentionally induced in the RCS by adjusting the trim sextupoles. It appears that our vertical instability is not a classical head-tail instability [1] . More data analysis and experiments were performed to characterize the instability.
doi:10.1109/pac.2007.4441132 fatcat:c6iim6u4pze6zebyyvymakbime