Wk report a cooling and deceleration experiment of a thermal beam by u
sing a nearly resonant red-shifted diffuse light in an optical integra
l sphere cavity. By using of this red-shifted diffuse light, the veloc
ity of a part of thermal sodium atoms is cooled to 380 m/s and the vel
ocity width of cooled atoms is agent 18 m/s. The mechanism of this kin
d of laser cooling and the experimental results are discussed.