Walive Pathiranage, M.R.P. Gurevich, A.V. JACoW Publishing Geneva, Switzerland 2673-5504 978-3-95450-234-9 10.18429/JACoW-SRF2023-MOPMB019 English 114-118 cavity simulation radio-frequency SRF superconductivity Contribution to a conference proceedings 2023 2023-09 https://doi.org/10.18429/JACoW-SRF2023-MOPMB019 https://jacow.org/srf2023/papers/mopmb019.pdf We report calculations of a dc superheating field Hs in superconductors with nanostructured surfaces. Particularly, we performed numerical simulations of the Ginzburg-Landau (GL) equations for a superconductor with an inhomogeneous profile of impurity concentration, a thin superconducting layer on top of another superconductor, and S-I-S multilayers. The superheating field was calculated taking into account the instability of the Meissner state at a finite wavelength along the surface depending on the value of the GL parameter. Simulations were done for the materials parameters of Nb and Nb₃Sn at different values of the GL parameter and the mean free paths. We show that the impurity concentration profile at the surface and thicknesses of superconducting layers in S-I-S structures can be optimized to reach the maximum Hs, which exceeds the bulk superheating fields of both Nb and Nb₃Sn. For example, a S-I-S structure with 90 nm thick Nb₃Sn layer on Nb can boost the superheating field up to ~ 500 mT, while protecting the SRF cavity from dendritic thermomagnetic avalanches caused by local penetration of vortices.