  The vacuum radiation of a massive scalar field is studied by means of a
single moving mirror. The field equation with an arbitrary-shaped mirror moving
in $(d+1)$ dimensions is given perturbatively in the non-relativistic limit.
Explicit results are obtained for a flat mirror moving in $(1+1)$ dimensions
and $(3+1)$ dimensions. The vacuum radiation power and vacuum friction force on
the mirror are given in $(1+1)$ dimensions. The intrinsic mass of the field is
found to suppress the vacuum radiation. In $(3+1)$ dimensions, the modification
of the frequency spectra and angular spectra of emitted particles due to the
intrinsic mass are obtained. In the limit of $m\to 0$, we recover the results
of the massless field.
