Ionization cooling of muons by strong focusing with a field of longitudinal current

Considered is the kinetics of ionization cooling of muons in a medium carrying a longitudinal current of high density which provides strongly focused particles, reducing the equilibrium value of the transverse beam emittance determined by multiple scattering to a minimum. As an alternative to the longitudinal current, solenoidal field focusing associated with cooling is shortly considered. This, however, leads to a rather small efficiency compared to longitudinal current focusing.