Protection Scheme Effectiveness Study for the High-Luminosity LHC MBRD Magnet

Abstract

The MBRD (Main Bending Recombination Dipole, or D2) is one of the magnets in the interaction region of the LHC that needs to be replaced in order to fulfill the requirements of the High-Luminosity upgrade. The magnetic field must be increased up to 4.5 T in an aperture with a diameter of 105 mm and a total length of about 8 m, to reach the target integrated field of 35 T <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\cdot$</tex-math></inline-formula> m. The increase of the magnetic field and, consequently, of the cross talk between the two apertures having the same polarity required a brand-new design characterized by asymmetric left-right coils and aluminum rings around the two apertures in order to compensate the repulsive Lorentz forces arising between them. The design was carried out at INFN, while the construction is taking place at the ASG Superconductors (Genova, Italy). The development plan was to initially build a 1.6 m long model, completed and cold tested in summer 2020, a full scale prototype, whose cold tests are now ongoing, followed by a series of six magnets, presently under construction. The test campaign performed on the short model and the one currently underway on the prototype provide very useful information for the magnets of the series, such as the behavior of the protection circuit in case of quenches. During the measurements performed at CERN, several quenches induced by the quench heaters were provoked, and the magnet behavior was recorded for different initial currents. This contribution will focus on the results of such tests and their comparison with the predictions obtained through the simulations with two different codes, Roxie and STEAM-LEDET.