{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"c235859ffd7059a068d85cea78edbac802ad0180c40cc2c6d5c271b7e8f29c3f","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["40b13bb9c15e4dfcbd63e7634aca11bdbf79b5a5557bef5cebecd3ae5ceb7746","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"a32f6ecb34037ade9a5802bbf5c5c69126f64f224347f7322f7be8d1ccc4abc1","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"beams.muon-ionization-cooling.final-emittance","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"The last cooling stage must reduce the beam width to about 25 microns while letting it spread lengthwise only within a set limit. No design has yet met both goals together.","posed_since":"","precise":"Muon collider design studies (MAP, the US Muon Accelerator Program, then IMCC, the International Muon Collider Collaboration) set normalized emittance targets of about eps_T ~ 22.5 to 25 micron transverse and eps_L ~ 70 mm (7.5 MeV m) longitudinal at the end of cooling. Determine whether a final-cooling channel using very high field solenoids ($B \\sim 300 \\text{ to } 400\\,\\mathrm{kG}$) or thick wedge absorbers reaches eps_T <= 25 micron with eps_L <= 75 mm and muon transmission above $\\sim 50\\%$, including decay losses.","problem_ref":"40b13bb9c15e4dfcbd63e7634aca11bdbf79b5a5557bef5cebecd3ae5ceb7746","references":"","settled_by":"End-to-end tracking of a realistic final-cooling lattice with engineering-feasible magnets meeting the targets, later confirmed by a demonstrator.","status_note":"Thick-wedge final-cooling designs (2024) and a 2026 dispersion-suppressor study for them aim at the 22 micron transverse target; meeting both targets in one realistic lattice is not yet shown.","title":"Can final cooling reach collider transverse emittance with acceptable longitudinal 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