• E. Plouviez, L. Farvacque, J.M. Koch, J.L. Pons, F. Uberto
  ESRF, Grenoble

Until 2008, the suppression of the closed orbit distortion on the storage ring of the ESRF was obtained using two separate systems: A slow system using 224 BPM and 96 correctors performing a correction every 30 seconds, and a fast system, using only 32 BPMs and 32 correctors but working at 4.4KHz, damping the orbit distortion from 50mHz up to 150Hz; the 15mHz to 50mHz frequency span was left uncorrected. This separation of the frequency ranges of the two systems avoided cross talks between them, but prevented the efficient cancellation of the very low frequency orbit distortions caused by the frequent modification of the insertion device settings during the beamlines operation. We now coordinate the operation of the slow and fast systems and suppress this dead frequency span. This paper describes the principle and the beneficial effect of this new scheme, and its limitations. To overcome these limitations, we are now developing a single new orbit correction system which will damp the orbit distortion from DC to 150Hz; this system will use the Libera Brillance BPM electronics recently implemented at ESRF, and new fast correctors. This new scheme is also briefly presented.