{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"51d5282d98428ec895a7334893fe406f8969b21aeb1df6653b6ec18924be9144","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5d1efa61f8a5cf2bb1992f7873ae2d4cb1c17df9c7d58978aa15b5876db768f5","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"f62386351f348b0605ea09da053416e57d29772c7247ea32d9249013f025276b","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"beams.sc-magnets.stress-degradation-limit","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"$\\mathrm{Nb_3Sn}$ is brittle, and the huge magnetic forces in a high-field magnet squeeze the cable until its ability to carry current is permanently damaged; where that threshold lies and what breaks first is uncertain.","posed_since":"","precise":"Rutherford cables of $\\mathrm{Nb_3Sn}$ filaments in epoxy-impregnated coils at fields up to $\\sim 1.6 \\times 10^{5}\\,\\mathrm{G}$ are under transverse stress of order $1.5 \\times 10^{9} \\text{ to } 2 \\times 10^{9}\\,\\mathrm{dyn}/\\mathrm{cm}^{2}$ (approximate). Determine the stress at which the critical current degrades irreversibly, its dependence on filament layout, impregnation and temperature cycling, and the microscopic failure mode (filament cracking, void collapse, debonding), as a function that fixes the maximal practical dipole field.","problem_ref":"5d1efa61f8a5cf2bb1992f7873ae2d4cb1c17df9c7d58978aa15b5876db768f5","references":"","settled_by":"Critical-current measurements of cable stacks under calibrated transverse stress, combined with post-test microscopy of filament cracks and a model that reproduces the onset stress.","status_note":"","title":"Transverse-stress limit for irreversible degradation of $\\mathrm{Nb_3Sn}$ cables","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"61e82fb05c4f969ccaceb183a570e2e223538c8a65e3cd2b6aae4a5f31534460","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"6237ea90de93cacb1a6c5bfaa2b805fbf799dd770cd4b48fabe38e2be23f49d0","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"Vat8QAefvxuxWfgh2vrGIRd9K_h2GVHxBVBJrTNwF3aCeI1rHU4eyoSekSw7nWu29cqORQeRIaIHFrSLPIvKCg"},"schema":"pubphys.envelope/1"},"record_hash":"61e82fb05c4f969ccaceb183a570e2e223538c8a65e3cd2b6aae4a5f31534460","leaf_index":2524}