{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"0739d8e4fe11b665777583a48d6312d2df01bb25716b67ffc687aab01f4a84ff","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["a9bb266f14d9000cb0f87bedef935b4ae9c212c5f10811d7f61372c78d3d3e87","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"43250a5fd7afc2d7f863930ed770706f1411035afc71f31898a11e497f47b36f","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":"2","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 $1.3 \\times 10^{-8}$ to $1.4 \\times 10^{-8}$ cm rad (ESRF-EBS, from 2020) and about $4 \\times 10^{-9}$ cm rad (APS-U, from 2024). Determine the minimal equilibrium eps_x at $E = 6\\,\\mathrm{GeV}$ and circumference $10^{5}-2 \\times 10^{5}\\,\\mathrm{cm}$ 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 < $10^{-9}$ cm rad (diffraction limit for $\\sim 10\\,\\mathrm{keV}$ photons) is attainable.","problem_ref":"a9bb266f14d9000cb0f87bedef935b4ae9c212c5f10811d7f61372c78d3d3e87","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"0ade57bd3ead13b629dbe98d109960461b67239ca975395c3812fa42d6aa749c","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"e78d1d5e833666ebbee6909e70d642ea7c260505f89a8e2c3ab1ba30ea2b4410","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"XfaCuSkIOsozgf-sOV7XwGyajdoWsRX4BGlSyLdUCUMDBcGOHsZKOkquCY1UFY3y15Qi-fHtM5R8s-kl0Xa8CA"},"schema":"pubphys.envelope/1"},"record_hash":"0ade57bd3ead13b629dbe98d109960461b67239ca975395c3812fa42d6aa749c","leaf_index":2460}