Orbit drift correction using correctors with ultra-high DAC resolution

At BESSY the planned continuous orbit drift correction could not go into routine operation as originally foreseen: the resolution of the 3 mrad correctors controlled by 16 bit DACs was insufficient and perturbed specific experiments unacceptably. Now a novel 2/spl times/16 bit coarse/fine type I/O board solved this problem while preserving the full dynamic range of the correctors. Permanent correction activity no more deteriorates experimental conditions. A typical orbit definition within +/- 5 /spl mu/m at more than 90% of the BPMs during a day is achieved. Even large perturbations caused by e.g. decaying superconducting wave length shifter currents or residual effects of undulator operations are adequately suppressed.