{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"6ea9fb42729c3e6e15fbe287f74cd1c41c6b19f8d201ab333f36ac58629e916a","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["91628ed177e96e50cb4b1e908fdd7876ed07b1198939d8e060097f0b18dd5c67","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"7293c8d215b1f4afd00dbf9711186f1a4bcc15b61ecba89e0eb05248c96b07db","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"beams.srf-cavities.high-field-q-slope","kind":"phenomenon","literature_status":"contested","n":"2","parents":[],"plain":"Above a certain field, niobium cavities start wasting far more energy; a two-day bake at 120 C removes the effect, and why it works is still debated.","posed_since":"","precise":"Electropolished bulk Nb cavities at $1.3\\,\\mathrm{GHz}$ and $T = 2\\,\\mathrm{K}$ show a steep drop of quality factor $Q_0$ above peak surface magnetic field $H_{\\mathrm{pk}} \\sim 900-1000\\,\\mathrm{G}$, removed by in-situ baking at $120\\,\\mathrm{C}$ for $\\sim 48\\,\\mathrm{h}$. Identify the mechanism (niobium nanohydride precipitation within $\\sim 10^{-5}$ cm of the surface, oxygen or vacancy-hydrogen complexes, or other) with a model predicting the onset field and its dependence on bake temperature and duration.","problem_ref":"91628ed177e96e50cb4b1e908fdd7876ed07b1198939d8e060097f0b18dd5c67","references":"","settled_by":"Depth-resolved measurement of hydrogen, oxygen and vacancy profiles before and after baking, correlated with $Q_0(H_{\\mathrm{pk}})$ of the same cavities and matched by a quantitative model.","status_note":"Hydride-precipitation and impurity (oxygen, vacancy-hydrogen) explanations each have supporting studies; no consensus was found in records checked through 2025.","title":"Mechanism of the high-field Q-slope and its cure by baking","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"33873c854833a0ae6f539bbbb12dbda67842c4bc33912a28fc66a15962b98952","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"4b5efac84c0b6bf20037fa7ed8f0508c9b6f7a8be74064b4200c719397f369ff","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"Rwf2AlJxCy9_ckRdCWepUMK1ToGRvQcbmWOCT_q8Q7yb_0AXTjnV7CgwfNPesGVQCp4Xrgdvm7Qv0p4XTc6-Aw"},"schema":"pubphys.envelope/1"},"record_hash":"33873c854833a0ae6f539bbbb12dbda67842c4bc33912a28fc66a15962b98952","leaf_index":2536}