{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"f33e6f5bc3d95c7e16b2b86c8db6367dbc9a56039b8273c9c6dc1f1d660c0b06","created":"2026-10-03T07:17:56Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"7a295b1b1ec2f31ff1790362f53dd8941b1d13a541d9e1ed5a9e4ddbf076d4b1","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"beams.fel-physics.slice-energy-spread","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Lasing needs electrons of nearly identical energy, and measured energy spreads in x-ray FEL electron beams have come out larger than models predicted.","posed_since":"","precise":"In photoinjectors with $1e8\\ \\text{to}\\ 1e9$ electrons per bunch, determine the contributions of intrabeam scattering, shot-noise-seeded microbunching instability and cathode emission to the slice energy spread $\\sigma_E$ (few keV) at injector exit and after bunch compression, and predict $\\sigma_E$ within $20\\ \\mathrm{percent}$ of measured values at several facilities.","problem_ref":null,"references":"","settled_by":"High-resolution slice energy spread measurements versus bunch charge and laser-heater setting compared with a start-to-end model including intrabeam scattering.","status_note":"Measurements at FEL injectors in the early 2020s attributed much of the excess to intrabeam scattering; quantitative agreement across facilities is not established.","title":"What sets the uncorrelated energy spread of high-brightness electron beams","topic_ref":"62fcdc9c8f916869de7ec88dba711f39f0c92f912f69f270978376119dc0bcaa"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"f7cab580d7739cf1f7bcdec9f6049a651c24e54a9edbf2c7b4e20adfd74cb281","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"07eecf0409dfc84b5ca054447cc8c38649e75484858b4d4880d147ba4905d4cc","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"IoRu0waFapwLS8eMOVqcqAQOtSPPi0qd7IRcFjwoqG-N-RXGQ4-QUyd1HLmKlbi0cNI_BjEO8YVjwuObbQyUBA"},"schema":"pubphys.envelope/1"},"record_hash":"f7cab580d7739cf1f7bcdec9f6049a651c24e54a9edbf2c7b4e20adfd74cb281","leaf_index":668}