THE MAGNETIC MODEL OF THE LHC DURING COMMISSIONING TO HIGHER BEAM INTENSITIES IN 2010-2011

The Field Description of the Large Hadron Collider (FiDeL) model is a set of semi-empirical equations linking the magnets behaviours established from magnetic measurements to the magnetic properties of the machine observed through beam measurements. The FiDeL model includes the parameterization of static and dynamic (time dependant) components. In the present paper, we outline the relationship between the beam observables (orbit, tune, chromaticity) and the model components during the commissioning to higher beam intensities in 2010-2011, with energy of 3.5 TeV per beam. The main relevant issues are (i) the operation at 10 A/s ramp rate and their influence on chromatic correction, (ii) the beta beating and its relation to the quadrupoles transfer functions and (iii) the origin of the observed tune decay at injection.