Compensation of longitudinal coupled-bunch instability in the Advanced Photon Source storage ring

Author

Karkay, K.C. ; Nassiri, A. ; Song, J.J. ; Kang, Y.W. ; Kustom, R.L.

Author_Institution

Adv. Photon Source, Argonne Nat. Lab., IL, USA

Volume

2

fYear

1997

fDate

12-16 May 1997

Firstpage

1575

Abstract

A longitudinal coupled-bunch (CB) instability was encountered in the 7-GeV storage ring. This instability was found to depend on the bunch fill pattern as well as on the beam intensity. The beam spectrum exhibited a coupled-bunch signature, which could be reproduced by an analytical model. The oscillations were also observed on a horizontal photon monitor. The beam fluctuations exhibited two periodicities, which were found to be correlated with the rf cavity temperatures. This correlation is consistent with the measured temperature dependence of the higher-order mode (HOM) frequencies. The HOM impedance drives the beam when brought into resonance with the CB mode by the temperature variation. Increasing the inlet cavity water temperature suppressed the instability. The experimental results are compared to an analytical model which characterizes the fill-pattern dependence. Studies to identify the offending HOMs are also presented

Keywords

X-ray production; electron accelerators; particle beam stability; storage rings; APS; Advanced Photon Source; HOM frequencies; beam intensity; bunch fill pattern; higher-order mode frequencies; higher-order mode impedance; inlet cavity water temperature; longitudinal coupled-bunch instability; periodicities; rf cavity temperature; storage ring; Analytical models; Fluctuations; Frequency measurement; Impedance; Monitoring; Optical coupling; Resonance; Storage rings; Temperature dependence; Temperature measurement;

fLanguage

English

Publisher

ieee

Conference_Titel

Particle Accelerator Conference, 1997. Proceedings of the 1997

Conference_Location

Vancouver, BC

Print_ISBN

0-7803-4376-X

Type

conf

DOI

10.1109/PAC.1997.750763

Filename

750763