Kapitza resistance at Niobium/superfluid He interfaces

by Dr Jay Amrit (Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur)

Tuesday 7 Oct 2014, 09:30 → 10:30 Europe/Rome

C. Villi meeting room (INFN-LNL)

Heat removal from SRF cavity walls to superfluid (HeII) plays a decisive on the thermo-magnetic stability and therefore on the performance of these cavities. The two main parameters are the thermal conductivity of Niobium and the thermal boundary resistance (Kapitza resistance) at the Niobium/superfluid He interface. Here we shall focus mainly on the Kapitza resistance .Theoretical models shall be present to demonstrate that the Kapitza resistance is anomalous at the Niobium/HeII interface, justifying the empirical experimental approach. Various sets of data shall be presented for polycrystalline and single crystal Niobium having different surface morphologies and bulk purities. The impact of surface impurities and dislocations on the Kapitza resistance shall be discussed. New analysis shall be present showing an intrinsic limit to the Kapitza resistance due to interactions between phonons (heat carriers) in He-II and the nanoscale surface roughness of Niobium surface. Potential future experiments shall be proposed.