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Abstract:
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For a long time voltage spikes (also called precursors) were measured while ramping up magnets, sometime leading to quench, other times not. These spike precursors have been seen as movements, but no qualitative detailed description of the events has been given.
Measurement data from coil voltage, magnetic pick-up coils and current during the precursor transients have been acquired and analysed for the Nb3Sn-dipole magnets FRESCA2 and 11T models—named MBHSP107 and MBHSP109. The measurement data is compared to movement simulations that were done with the ROXIE-program, used to calculate mutual inductance change for a number of different movement types in these magnets. The study strongly suggests that the transients are caused by movements, and also indicates that the maximal length of a single slip-stick motion can be up to around 10 µm, mostly in the direction of the magnet’s internal forces. The study has proven that transients in measurement data occur due to coil movements. This study has been performed by Marcus Wallin, who completed his master thesis on this topic in 2019, see EDMS 2254195