Parametric field modeling for the lhc main magnets in operating conditions

The first beam injections and current ramps in the LHC will require a prediction of the settings of the magnet current as well as the main correctors. For this reason we are developing a parametric model of the magnetic field generated by the LHC magnets that will provide the field dependence on current, ramp-rate, time, and history. The model of the field is fitted on magnetic field measurements performed during the acceptance tests of the magnets before their installation in the machine. In this paper we summarize the different steps necessary to select the relevant data and identify the parameters: the data extraction, the filtering and the validation of the measurements, and the fitting procedure that is used to obtain the parameters from the experimental results. The main result reported is a summary of the value of the parameters obtained with the above procedure, and describing the behavior of the magnetic field in the LHC main dipoles and quadrupoles.