Magnetic Field tracking experiments for the LHC

by Valeria Granata (CERN-AT)

Thursday 13 Nov 2003, 14:15 → 15:15 Europe/Zurich

AT Auditorium (CERN)

One of the fundamental requirements during the energy ramp of the LHC is that the ratio between the field produced by the quadrupoles and the field in the dipoles remains constant in order to minimize the variation of the betatron tune that could induce particle loss. A series of tracking experiments was devoted to demonstrate that this ratio can be maintained constant to better than 10^-4 throughout the same current ramp as foreseen for the LHC. The reproducibility of the measurements has been verified. A description of the measurement set up is given. The procedure employed to analyse the data and calculate the magnetic field is shown. The methods used to optimise the dipole and quadrupole current ramps for obtaining the required ratio of B2/B1 are presented. The same equipment was used to verify that modulation of the quadrupole current in the LHC is possible (so-called k-modulation). The results of the measurements performed by modulating the current with a harmonic function demonstrate that it is possible to modulate the strength of an individual quadrupole to determine the magnetic center through beam-based measurements.