Impact of 440 GeV Proton beams on Superconductors in a Cryogenic Environment

The superconducting magnets used in high energy particle accelerators such as CERN’s LHC can be impacted by the circulating beam in case of specific failures. This leads to interaction of the beam particles with the magnet components, like the superconducting coils, through direct beam impact or via secondary particle showers. The interaction causes energy deposition in the timescale of microseconds and induces large thermal gradients within the superconductors, which are in the order of 100 K/mm. To investigate the effect on the superconductors, an experiment at CERN’s HiRadMat facility was designed and executed, exposing short samples of Nb-Ti and Nb$_3$Sn strands in a cryogenic environment to microsecond 440 GeV proton beams. The irradiated samples were extracted and analyzed for their critical transport current $I_c$. This paper describes the results and analysis of the measurements of $I_c$ as well as thermo-mechanical simulations of the Nb3Sn strands to evaluate the degradation of $I_c$ as a function of the mechanical strain present during and after the beam impact.