{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"f4ed96a9761c35bb2eb8a946cdb854edce8281616fb36d8ccd422d2d6acc74aa","created":"2026-10-03T07:17:56Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"e377048a2df7352a60d9ce396b6a1fa28f6a4d8cf06abd8961c078e76b919e72","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"beams.csr-microbunching.3d-csr-emittance-growth","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Standard models treat the bunch as a thin line, which fails for bunches that are wide compared with their length; the blow-up of such wide, compressed bunches is not reliably predicted.","posed_since":"","precise":"The 1D steady-state CSR wake for a bunch of rms length $\\sigma_z$ on a bend of radius $R$ is valid when the transverse size satisfies $\\sigma_x << (\\sigma_z^2 R)^{1/3}$. For magnetic bunch compressors where this inequality fails ($\\sigma_z \\sim 1e-4$ to 1e-3 cm, 1e8 to 1e10 electrons per bunch), compute projected and slice emittance growth including the transverse variation of the radiation field, transient fields at magnet entrance and exit, and vacuum-chamber shielding, and state the parameter region in which the 1D model errs by more than a factor 2.","problem_ref":null,"references":"","settled_by":"Self-consistent 3D field calculations benchmarked against slice-emittance measurements downstream of a chicane scanned across $\\sigma_x \\sim (\\sigma_z^2 R)^{1/3}$.","status_note":"3D CSR codes have been developed since the 2000s, but measured benchmarks in the regime where the 1D model fails remain few (2024-2026 literature not checked in detail).","title":"Emittance growth from three-dimensional coherent synchrotron radiation in compressors","topic_ref":"5a86adf3ddd836ff2ccead3d8facd2c7c42ba046664278d11978618137dcefd5"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"40a081cf1906d471195856c9495a422a86b867e04a1598cded570923fcdc6577","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"6f778df17fc080605423f6be9105fd495e846e554c79e6a09826ef90a9689bde","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"j6EbS4hlbe_EJ5ATkcOtPAFcZSiVVfw_xCf9iG36aQIPekxYfhLuS2wVrn4JtT3yk9UqVwaY1JZJvpuHc0zrAg"},"schema":"pubphys.envelope/1"},"record_hash":"40a081cf1906d471195856c9495a422a86b867e04a1598cded570923fcdc6577","leaf_index":661}