Transfer functions for the ALS lattice magnets

The primary purpose of the magnetic measurements performed on the ALS storage-ring lattice-magnets was to ascertain their compliance with the strict tolerances established for this third-generation synchrotron light source. In the course of the data evaluation, a novel approximation method has been developed that leads to four-parameter representations of all magnet transfer-functions, and includes saturation and residual field effects. These transfer functions were used to change the standard working point of the ALS storage ring at 1.5-GeV beam energy from the upper to the lower hysteresis branches, and later to ramp the ring energy from 1.5 GeV to the maximum design value of 1.9 GeV in one uninterrupted process that did not require any intermediate tune correction. Likewise, predicted magnet set values for 1.0-GeV conditions were applied and very closely led to the standard betatron tunes