{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"22b162f214376fc339ad710f331999b35a5a11bed89512653f05bc8a13d002d5","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["40a081cf1906d471195856c9495a422a86b867e04a1598cded570923fcdc6577","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"50ce29c569833ac4752fb0941e3879c641c36a65d7206173ed580a4c62f58d08","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":"2","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 ($\\sigma_z \\sim 10^{-4}$ to $10^{-3}$ cm, $10^{8}$ to $10^{10}$ 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":"40a081cf1906d471195856c9495a422a86b867e04a1598cded570923fcdc6577","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"21b7a19564f6a207942b35c6c7a45edfdfb5fa5b0264efebdab1fb9c2121abc1","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"e80cf93dca2423b2140953e405d23ed2a7eef29fa99359e44046515c800358f6","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"Gvs936XWL1np2QpeP8mV2ZnEyK6e4Nr5HruvkpAIIPBGzbNpmRsmzFCCegwqpQWwotvifu8yFDZjyKBDwky0Dw"},"schema":"pubphys.envelope/1"},"record_hash":"21b7a19564f6a207942b35c6c7a45edfdfb5fa5b0264efebdab1fb9c2121abc1","leaf_index":2470}