{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"094b8825b65805605380d3387ce28af16b265b8da99394c5129d88d9f7369845","created":"2026-10-03T07:17:56Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"76d6d844f1df21317bc503c85504ad78d8b92fc198b7edd3b4a263dbcd899e67","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"beams.nb3sn-cavities.exceed-nb","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"The goal of Nb3Sn is to go beyond niobium, but so far niobium still holds the gradient record. The question is whether any Nb3Sn cavity can beat it.","posed_since":"","precise":"Determine whether a Nb3Sn-coated 1.3 GHz elliptical cavity can sustain $E_{\\mathrm{acc}}>0.45\\,\\mathrm{MV}/\\mathrm{cm}$ ($B_{\\mathrm{pk}}>1900\\,\\mathrm{G}$) at any temperature with $Q_{0}>1e10$, or whether intrinsic film properties (grain boundaries, thin-film thermal limits) forbid it.","problem_ref":null,"references":"","settled_by":"A Nb3Sn cavity test exceeding the Nb record gradient, or a demonstrated intrinsic bound below it.","status_note":"","title":"Can a Nb3Sn cavity exceed the gradient of the best niobium cavities","topic_ref":"73a350cdcc5f735b0cb472211fcfb487c1e4da9b53f0fa2340cf5e90142abf8f"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"2c5794513268a91b15d1ae24d7fd99ca1992f261eecd5d4f3b7c3cee57a4b788","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"5ca6290d4ac5826ef4ab428b4157548dc921350a56690f9091885aa6c625edfa","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"sxQdvinOwrpHwSlBj7YtANiOCDjDxy6bBqX2JnqCLAcZ4vz5Z4fIRTy_ELlFAqmeXSVZd0ls4dKwgVn7frloCg"},"schema":"pubphys.envelope/1"},"record_hash":"2c5794513268a91b15d1ae24d7fd99ca1992f261eecd5d4f3b7c3cee57a4b788","leaf_index":676}