Continuous wave (CW) operation of superconducting cavities for particle acceleration is the enabling technology for several projects in research and industry.
Minimizing the losses of superconducting cavities is essential for their realization and can yield huge cost savings. The initial investment cost is reduced by the need for a smaller cryogenic infrastructure and the operation costs are lowered due to reduced energy consumption.
Currently almost all superconducting cavities used in particle accelerators are made of niobium. In most cases their power dissipation is up to 10 times greater than predicted by theory. An explanation is still lacking. Recent improvements in performance have been achieved through high temperature baking in vacuum or controlled environment, but the results are not always reproducible. Thus there is research on this technology needed for reliable high-yield production of cavities with lowest losses for CW operation. To reach energy consumption below the limit of niobium it has been proposed to coat cavities with nanometre thin alternating layers of superconductors and dielectrics. By this approach the cryogenic load for CW operation may be reduced to a fraction compared to bulk niobium cavities or operation at higher temperatures may become feasible.
In this project we plan to push the limit of lowest energy consumption of superconducting cavities in the near and far future. For the optimization of accelerators for the near future we plan to investigate heat treatments on bulk niobium cavities to push this technology even closer to its fundamental limit. Additionally we plan to produce samples of multilayers. These will be tested in two unique RF surface resistance characterization systems to experimentally investigate the potential of this approach. Additionally the shielding performance of the materials will be investigated by three independent techniques; muon spin rotation, beta-NMR and polarized neutron tomography.
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