{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"07bfcc70d895f8dbeb51316216ece699009f3d76c53b9dbccf76824ab4ccfa0e","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b","f7cab580d7739cf1f7bcdec9f6049a651c24e54a9edbf2c7b4e20adfd74cb281"],"salt":"f38b20c480d53b2b2a6dc016febe4b4060e0b2447efb9733ac48411c907f4b37","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":"2","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 $10^{8}\\ \\text{to}\\ 10^{9}$ 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 $20\\%$ of measured values at several facilities.","problem_ref":"f7cab580d7739cf1f7bcdec9f6049a651c24e54a9edbf2c7b4e20adfd74cb281","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"957214e37a85f417c0e8be228f1bb82e50b5e290db2aef446f539edcd492bd55","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"e1b1572f539fef827ae4465b387d7e0c0693e1a64b0ab20ad925f133d7d4e1ed","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"mf_i7PW39_BP64WUkxXvadGYXH9wrMKXFQP53rDtR7LFWRSMid3jXnmr4S0GuEZJxrFra57LuAgGF0Q1p86ABA"},"schema":"pubphys.envelope/1"},"record_hash":"957214e37a85f417c0e8be228f1bb82e50b5e290db2aef446f539edcd492bd55","leaf_index":2482}