Validation of the Protection Scheme for the HL-LHC MBRD Magnet by Simulations and Prototype Tests

The High-Luminosity upgrade of the Large Hadron Collider (LHC) (Todesco et al., 2021) foresees the replacement of the magnets around the interaction points of the ATLAS and CMS experiments at CERN. One of the new magnets is the separation-recombination dipole, also called Main Bending Recombination Dipole (MBRD)(Caiffi et al., 2021), (Levi et al., 2022) in the D2 cryomagnet assembly. It consists of a cosine-theta, double aperture with same polarity, winded with a Nb-Ti Rutherford cable, with a central field of 4.5 T and a magnetic length of 7.78 m, which generates an integrated magnetic field of 35 Tm, inside of a bore 105 mm in diameter. The magnet is a collaborative effort with a design and production follow up by INFN Genova, production by ASG Superconductors, cold mass assembly and test by CERN. One 1.6 m short model and a full-scale prototype have been fully tested, while four series magnets and 2 spares are currently being built. To cope with a stored energy of 2.2 MJ in the single layer magnet, the quench heater technology has been optimized and dimensioned to limit the hot spot temperature to 300 K. This paper will describe the design choices for the tested protection scheme and the results obtained by the test, including failure case studies. The data will be compared to the STEAM-LEDET (Ravaioli et al., 2016) simulations and used to further validate the modeling parameters. With the obtained results from the tests and from modeling, the protection scheme has been validated and will be applied in the series magnet production.