Low-$\beta$ Quadrupole Movements as Source of Vertical Orbit drifts at LEP

In LEP, the superconducting low-beta quadrupole magnets (QS0) are a major source of vertical orbit drifts. During the 1995 LEP operation, measurements of the vertical movements of these quadrupoles were taken systematically for the first time. The analysis described in this note gives clear evidence for the correlation between the mechanical movements of the magnets and the drifts of the vertical orbit. This opens the possibility for a feedback system to prevent large vertical orbit drifts.