{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"ad72ace5297d138367c64043431736fe18acc3ec52ab9f768155687d0e2cb134","created":"2026-10-03T07:17:56Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"a3bdbe3f8b25a6bdfeca99066d32105ebae92110a022e0b9efdf83e9f76bb377","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"beams.beam-brightness.ring-ultimate-emittance","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"New diffraction-limited synchrotron rings shrink the beam until the x-rays are nearly coherent; collisions within the bunch and loss of stable orbits set a floor that is not yet known.","posed_since":"","precise":"Multibend-achromat rings at $6\\,\\mathrm{GeV}$ operate with natural horizontal emittance eps_x of about 1.3e-8 to 1.4e-8 cm rad (ESRF-EBS, from 2020) and about 4e-9 cm rad (APS-U, from 2024). Determine the minimal equilibrium eps_x at $E = 6\\,\\mathrm{GeV}$ and circumference $1e5-2e5\\,\\mathrm{cm}$ with intrabeam scattering at full current, Touschek lifetime above $1\\,\\mathrm{h}$, and dynamic aperture adequate for on-axis or off-axis injection, and whether eps_x < 1e-9 cm rad (diffraction limit for $\\sim 10\\,\\mathrm{keV}$ photons) is attainable.","problem_ref":null,"references":"","settled_by":"A lattice optimization with these constraints giving $\\mathrm{eps}_x$ versus circumference, checked against operating fourth-generation rings.","status_note":"","title":"Lowest equilibrium emittance reachable in electron storage rings","topic_ref":"3311684a3644100d5c4072cc7fb5698b312b296ec8b7139e230fbc39301d2361"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"a9bb266f14d9000cb0f87bedef935b4ae9c212c5f10811d7f61372c78d3d3e87","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"2ca1e65cb3e48f231e57067223cf2aae33fe4263b8476e34b0b441d4be5288df","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"6Oy20SAfub7hgSqb9sGJ5oSBCSzg-7FCNBSI39D-k6Ewla7q8iEsnVAgbNazj7i15DA8LOA5fajJqOBWWLxXDQ"},"schema":"pubphys.envelope/1"},"record_hash":"a9bb266f14d9000cb0f87bedef935b4ae9c212c5f10811d7f61372c78d3d3e87","leaf_index":648}