Simulation of quench dynamics in SRF cavities under pulsed operation

As has been well verified both theoretically and experimentally in steady state, the thermal stability of SRF (superconducting radio-frequency) cavities strongly depends on the material properties of niobium such as RRR (residual resistivity ratio) and the presence of material defects on the surface. Recently, SRF technology has been chosen for pulsed machines such as the Tesla Test Facility (TTF), the Spallation Neutron Source (SNS), and the European Spallation Source (ESS). In order to guide the selection of operational limits and materials, an understanding of dynamics of quenching in pulsed operation is important. For this purpose, a universal thermal stability analysis algorithm is set up. With the help of 3D FEM codes, a series of transient, non-linear and self-correlated analyses are carried out. This scheme may be used for any stability analysis in SRF cavities with arbitrary conditions such as 3D structure, varying material properties, transient behavior, non-linear material properties, etc.