Hall, D.L. Liarte, D. Liepe, M. Porter, R.D. Sethna, J.P. JACoW Geneva, Switzerland 978-3-95450-191-5 10.18429/JACoW-SRF2017-THPB042 English 844-847 THPB042 ion cavity niobium site SRF Contribution to a conference proceedings 2018 2018-01 https://doi.org/10.18429/JACoW-SRF2017-THPB042 http://jacow.org/srf2017/papers/thpb042.pdf The amount of residual resistance gained per unit of trapped flux ' referred to as the trapped flux sensitivity ' in Nb3Sn cavities has been found to be a function of the amplitude of the RF field. This behaviour is consistent with a scenario in which the trapped vortex dynamics are described by collective weak pinning. A model has been developed to describe this, and results in the observed linear dependence of trapped flux sensitivity with RF field. The model is used to discuss cavity preparation methods that might suppress this dependence, which would reduce the trapped flux requirements necessary to operate an Nb3Sn cavity at simultaneous high quality factors and accelerating gradients.