Analysis of impregnated Niobium-Tin coils for the High-luminosity LHC magnets

The High-luminosity project of the LHC calls for the employment of a new technology of superconducting magnets, which will make use of a material never used before, Nb3Sn. Some of the dipole magnets will be replaced inside the accelerator to enhance the collimating system of the beams and will be capable of producing magnetic fields in the order of 12 T, against the 8 T of the present machine. Experimental tests were conducted at the cryogenic laboratory at CERN to study the thermal behavior of a sample of the 11 T dipole under AC losses, with typical values of the input power density in the order of the mW/cmᵌ. The sample was inserted into an open box of insulator, to get closer to real operation. This thesis, which was carried out at the MSC (Magnets, Superconductors and Cryostats) Group at CERN, regards the development of a 1-D model of a radial line crossing the middle plane of a quadrant of the magnet. It is also representative of the materials in the section and it was used with the aim to study the temperature evolution and steady-state profiles in response to heat injections in the conductors, similar to those provided in the experiment. The same model was adapted to reproduce results of quench tests carried out at the SM-18 facility on short models of the 11 T dipole. In such tests, inductive heaters were energized to release heat in the magnet, in order to trigger the quench phenomenon, starting from given operating conditions of current and field. Using magnetic field maps together with the parametrization of the superconducting material, it was possible to derive local values of the T_cs, thus employing the magnet as a temperature probe. This work presents a detailed description of the model and of the hypothesis made to run the simulations, together with its validation obtained through the comparison with experimental tests cited above.