  Given their 2.2 microsecond lifetime, muons must be accelerated fairly
rapidly for a neutrino factory or muon collider. Muon bunches tend to be large.
Progress in fixed field, alternating gradient (FFAG) lattices to meet this
challenge is reviewed. FFAG magnets are naturally wide; low momentum muons move
from the low field side of a gradient magnet to the high field side as they
gain energy. This can be exploited to do double duty and allow a large beam
admittance without unduly increasing the magnetic field volume. If the amount
of RF must be reduced to optimize cost, an FFAG ring can accommodate extra
orbits. I describe both scaling FFAGs in which the bends in each magnet are
energy independent and non-scaling FFAGs in which the bends in each magnet do
vary with muon energy. In all FFAG designs the sum of the bends in groups of
magnets are constant; otherwise orbits would not close. Ways of keeping the
accelerating beam in phase with the RF are described. Finally, a 1 MeV proof of
principle scaling FFAG has been built at KEK and began accelerating protons in
June 2000 with a 1 kHz repetition rate.
