{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"fe97cc2696faeb99cabe322e7396b1872ead05d4a53e81d9d52e4562a2bd5673","created":"2026-10-03T07:17:56Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"0dc8b8b47ce7765ee9fdb3dd265becd0cde71ffc452b938c2ffb03dada101801","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"beams.srf-cavities.residual-resistance-floor","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Even far below the superconducting transition, cavities keep a small leftover energy loss whose sources are only partly identified.","posed_since":"","precise":"At $T <\\sim 1.5\\,\\mathrm{K}$, where the BCS surface resistance at 1.3 GHz is negligible, the quality factor of the best Nb cavities saturates at $Q_0$ of order 1e11 (residual resistance $\\sim 1-3\\,\\mathrm{nOhm}$), set by a temperature-independent residual surface resistance. Determine the fractions contributed by trapped magnetic vortices, two-level systems in the surface Nb2O5 oxide, and subgap quasiparticle states, as functions of field, frequency and surface treatment.","problem_ref":null,"references":"","settled_by":"Measurements of residual resistance versus trapped flux, frequency and field, combined with oxide removal or regrowth, that separate the three contributions.","status_note":"","title":"What sets the residual surface resistance floor of niobium cavities","topic_ref":"e80fdf5b356ba02d4b3990f8abe874d0448c454195c990a76c551f83781fb3d8"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"a03adf8929526af28c3ccb8aebc93561e72f4fe6a087b541161396b3e506dec2","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"8ede790861f4f72ce6536d283e808607dfe67966203f90c07c51608cf5a80892","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"-Nt4geOUsqT4Y2NVqfbNPl8DojQN8w8l8HFCcith6FXjLmwrzAJcMjeXGRJ2CrFeGfuA9sWwmE0VZDuArTl3AA"},"schema":"pubphys.envelope/1"},"record_hash":"a03adf8929526af28c3ccb8aebc93561e72f4fe6a087b541161396b3e506dec2","leaf_index":706}