  We study quantum radiation generated by a uniformly accelerated motion of
small spherical mirrors. To obtain Green's function for a scalar massless field
we use Wick's rotation. In the Euclidean domain the problem is reduced to
finding an electric potential in 4D flat space in the presence of a metallic
toroidal boundary. The latter problem is solved by a separation of variables.
After performing an inverse Wick's rotation we obtain the Hadamard function in
the wave-zone regime and use it to calculate the vacuum fluctuations and the
vacuum expectation for the energy density flux in the wave zone.
