The HL-LHC Short Model Recombination D2 Dipole: Cold Test Results and Analysis

The new D2 recombination superconducting dipole is a key two-in-one Nb-Ti magnet with a 105 mm bore aperture for the high luminosity LHC accelerator upgrade project (HL-LHC) at CERN expected in operation from 2024. A short model MBRDS1 magnet of 1.6 m magnetic length has been designed by INFN (Genova), built by ASG Superconductors, and cold tested at CERN within a INFN - CERN collaboration framework. This model magnet features novel magnetic and mechanical design elements, which include the cancellation of unwanted cross-talk field multipoles through asymmetric coils, aluminium alloy collar pack preloading rings and a dedicated axial structure design. The future series of four 8.5 m long full-length dipole magnets shall be installed on both sides of the ATLAS and CMS interaction points with an integral field of 35 T.m and 4.5 T bore magnetic field. This paper presents the first power test results including training, protection, and field quality. Short model results will give a relevant feedback for the prototype construction and the series production.