The LHC magnetic field model

Abstract

The compensation of the field changes during the beam injection and acceleration in the LHC requires an accurate forecast and an active control of the magnetic field in the accelerator. The LHC Magnetic Field Model is the core of this magnetic prediction system. The model will provide the desired field components at a given time, magnet operating current, magnet ramp rate, magnet temperature and magnet powering history to the required precision. The model is based on the identification and physical decomposition of the effects that contribute to the total field in the magnet aperture of the LHC dipoles. Each effect is quantified using data obtained from series measurements, and modeled theoretically or empirically depending on the complexity of the physical phenomena involved. This paper presents the developments of the new finely tuned magnetic field model and evaluates its accuracy and predictive capabilities over a sector of the machine.