Study of damage mechanisms and limits of superconducting magnets due to beam impact.

Abstract

The damage mechanisms and limits of superconducting accelerator magnets due to the impact of high intensity particle beams are not sufficiently understood at present. Beam impact to magnets can happen at very different time scales, from ns to seconds. Most critical are so-called ultrafast losses happening when part of the beam is directly deflected into equipment. The protection of the LHC for ultra-fast beam losses depends on passive devices intercepting the lost beam. Damage in superconducting magnets due to particle showers from intercepted beam must be avoided. An example of an event that is not understood is the damage of small corrector magnets. During LHC run 1, three such magnets in the LHC inner triplet left of IP2 (IT.L2) have been found open after a failure that happened during injection; several magnets including the main quadrupole magnet where these correctors are mounted on the front face, quenched during this event. It is believed that a local shock heating, followed by mechanical shock waves can lead to a degradation of the cable strand insulation, damage the sc. filaments or the copper matrix. Improving the understanding of the damage mechanisms and reducing the uncertainty on the amount of beam losses below a critical limit is important in the view of current LHC operation, the planned increase in brightness of the beam injected into the LHC and in the view of the future HL-LHC and FCC. Within this thesis it is therefore proposed to study the different damage mechanisms due to beam impact. These mechanisms should be first investigated theoretically and in simulations. In a second step the feasibility of experimental verification of the dominating damage mechanisms should be studied and an experimental setup will be proposed for NbTi and Nb3Sn superconductive materials. Finally the damage mechanisms should be investigated experimentally and extrapolated to failure scenarios observed during LHC operation, expected for future operation and extrapolated to failure scenarios for HL-LHC (Crab cavities) and FCC.