Status of the LHCb dipole magnet

The LHCb experiment focuses on the precision measurement of CP violation and rare decays in the B-meson system. It plans to operate with an average luminosity of 2 × 10³² cm^-2s^-1 that should be obtained from the beginning of the LHC operation. The LHCb detector exploits the forward region of the pp collisions at the LHC collider. It requires a single arm spectrometer with a large dipole magnet of 4 Tm of total integrated field, having the capability to stand frequent polarity changes and providing good lateral field homogeneity. For reasons of cost, simplicity and robustness, a magnet with resistive coils has been chosen. The magnet has a free aperture of ±300 mrad horizontally and ±250 mrad vertically demanding a sloping gap of 2.2 to 3.5 m vertically (the direction of the field) and 2.6 to 4.2 m horizontally. The total weight of the magnet is about 1600 t. The power dissipation in the aluminum coils will be 4.2 MW. Low carbon steel plates of 100 mm thickness are used to assemble the yoke. The coils are wound from hollow aluminum conductor of 50 mm × 50 mm cross-section with a central cooling channel of 25 mm diameter. To reach good field quality the coils are bent by 45° toward the gap along the horizontal aperture and the pole pieces have large shims. The magnet design will be reviewed; the magnet assembly in the underground area of the experiment and test results will be reported.