The influence of static vacuum on the cluster size and density of the supersonic gas jet is studied by Raleigh scattering method. It is found that in a range from 3×10-4 Pa to 9.9×104 Pa, the static vacuum has very little influence on the cluster size and desnity. The self-limiting effect which was found for hydrogen cluster at liquid nitrogen temperature is also found for argon cluster at positions far from the nozzle, and it is found to play an important role in the cluster generation and transporation. The result is very valuable for the construction of the desktop neutron source based on laser fusion method, since the pumps and device to supply the vacuum can be reduced and simplified.