Development of the orbit feedback system for the VSX ring

An orbit feedback system will be installed in the VSX ring to stabilize the photon beam. The new COD correction method, the eigenvector method with co nstraints, is adopted for calculation of the steering-magnet currents. A co mputer simulation shows that the new method can tightly fix the beam positi ons at insertion devices, correcting the whole closed orbit globally with a lmost the same performance as the ordinary eigenvector method. A test VME u nit including DSP and shared memory boards is being developed for the fast feedback control and its performance test shows that the total feedback tim e is less than 1 ms (875 mus) except for the network and VME-bus transfer t imes related to the shared memory board. (C) 2001 Elsevier Science B.V. All rights reserved.