  We present a theoretical analysis of the coherent acceleration of atomic
Bose-Einstein condensates. A first scheme relies on the 'conveyor belt'
provided by a frequency-chirped optical lattice. For potentials shallow enough
that the condensate is not fragmented, the acceleration can be interpreted in
terms of sequential Bragg scattering, with the atomic sample undergoing
transitions to a succession of discrete momentum sidemodes. The narrow momentum
width of these sidemodes offers the possibility to accelerate an ultracold
atomic sample such as e.g. a Bose-Einstein condensate without change in its
momentum distribution. This is in contrast to classical point particles, for
which this kind of acceleration leads to a substantial heating of the sample. A
second scheme is based on the idea of a synchronous particle accelerator
consisting of a spatial array of quadrupole traps. Pulsing the trapping
potential creates a traveling trap that confines and accelerates the atomic
system. We study this process using the concept of phase stability.
