Can final cooling reach collider transverse emittance with acceptable longitudinal growth
In plain words
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.
Precise statement
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 $\sim 50\,\mathrm{percent}$, including decay losses.
What would settle it
End-to-end tracking of a realistic final-cooling lattice with engineering-feasible magnets meeting the targets, later confirmed by a demonstrator.
Status in the literature
Unverified 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.
Related problems
- Special case of Reaching muon collider target emittances by ionization cooling · Final-cooling stage is the last step of reaching muon collider emittances