Increase of Spin Polarization for Energy Calibration at LEP

The most accurate beam energy determination at LEP is based on a g-2 measurement of electrons via resonant depolarization of the beam. At beam energies beyond 45 GeV this method is limited due to d epolarizing effects. The compensation of depolarizing resonances was improved by reducing the beam deflection in the optical elements of the storage ring. Therefore the misalignment of the beam po sition monitors was detected with a dynamic beam based measurement and the mechanical misplacement of the quadrupole magnets was analysed. In addition, the machine parameters were optimised in orde r to minimise the excitation of depolarizing effects. During the 1997 LEP run it was possible for the first time to calibrate the beam energy at 55.3 GeV with resonant depolarization and to obse rve polarization at 60.6 GeV.