OPTICS PERTURBATIONS DUE TO DISCONTINUOUS REPLACEMENT OF RADIATED ENERGY

The synchrotron radiation loss per turn scales with the fourth power of the energy and therefore increases very rapidly when raising the LEP center-of-mass energy from 110 GeV up to a maximum of about 200 GeV. This causes the beam energies to vary by an amount as large as?r 0.3 % and the e+e- orbits to be different [l]. Since the reflection symmetry present in LEP is destroyed by the closed-orbit distortions remaining after correction, all the optics parameters, i.e. Twiss parameters, dispersions, tunes, are slightly different for e+ and e- bunches. As a direct consequence, the corrected closed-orbits of the two beams are also different and, in particular, the et and e- bunches would miss each other at the interaction ooints if their positions were not adjusted by fin