Abstract
It is shown that a multilayer comprised of alternating thin superconducting and insulating layers on a thick substrate can fully screen the applied magnetic field exceeding the superheating fields Hs of both the superconducting layers and the substrate, the maximum Meissner field is achieved at an optimum multilayer thickness. For instance, a dirty layer of thickness ∼0.1 μm at the Nb surface could increase Hs ≃ 240 mT of a clean Nb up to Hs ≃ 290 mT. Optimized multilayers of Nb3Sn, NbN, some of the iron pnictides, or alloyed Nb deposited onto the surface of the Nb resonator cavities could potentially double the rf breakdown field, pushing the peak accelerating electric fields above 100 MV/m while protecting the cavity from dendritic thermomagnetic avalanches caused by local penetration of vortices.
Highlights
It is shown that a multilayer comprised of alternating thin superconducting and insulating layers on a thick substrate can fully screen the applied magnetic field exceeding the superheating fields Hs of both the superconducting layers and the substrate, the maximum Meissner field is achieved at an optimum multilayer thickness
This paper addresses the limits to which the maximum screening field can be increased by S layers with given ds, λ and Hs deposited onto a thick Nb substrate with given λ0 and Hs0
The multilayer significantly reduces vortex dissipation as compared to the bulk Nb3Sn, yet a thin Nb3Sn layer with d ∼ 100 nm may only slightly increase the thermal impedance of the cavity wall, G = α−K1 + ds/ks + di/ki + dN b/kN b, where αK is the Kapitza thermal resistance
Summary
Alex Gurevicha Department of Physics and Center for Accelerator Science, Old Dominion University, Norfolk, Virginia 23529, USA (Received 4 September 2014; accepted 23 December 2014; published online 7 January 2015).
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