Decrease of the surface resistance in superconducting niobium resonator cavities by the microwave field
- Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)
- Department of Physics, and Center for Accelerator Science, Old Dominion University, Norfolk, Virginia 23529 (United States)
Measurements of the quality factor, Q, of Nb superconducting microwave resonators often show that Q increases by ≃10%–30% with increasing radio-frequency (rf) field, H, up to ∼15–20 mT. Recent high temperature heat treatments can amplify this rf field-induced increase of Q up to ≃50%–100% and extend it to much higher fields ≃100 mT, but the mechanisms of the enhancement of Q(H) remain unclear. Here, we suggest a method to reveal these mechanisms by measuring temperature dependencies of Q at different rf field amplitudes. We show that the increase of Q(H) does not come from a field dependent quasi-particles activation energy or residual resistance, but rather results from the smearing of the density of state by the rf field.
- OSTI ID:
- 22283078
- Journal Information:
- Applied Physics Letters, Vol. 104, Issue 9; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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