We have demonstrated the slowing of a beam of cold (180 K) metastable
neon atoms in a diffuse reflecting cylindrical cavity with monochromat
ic light. Using a well-collimated atomic beam entering the cavity, it
is shown that stimulated emission has a major effect on the transverse
velocity distribution. A large saturation parameter s results in a lo
ss mechanism for the center line beam intensity. A Monte Carlo simulat
ion shows that the light intensity should be evenly distributed with m
oderate saturation conditions, to optimize the slowing effect while mi
nimizing the transverse diffusion.