عنوان مقاله [English]
نویسندگان [English]چکیده [English]
In this paper, several prepared samples of copper and iron powder with a purity of 99% ,with various thicknesses of water, polyethylene and graphite moderators are irradiated in front of a isotopic Am-Be neutron source. Measuring the distance at which samples achieve the most amount of activity, the mechanism of neutron moderation in water, polyethylene and graphite moderators is investigated. Using obtained experimental results, maximum areas under the curve are plotted for each of water, polyethylene and graphite moderators. Comparison the plots related to iron and copper samples shows that the area under the peak for iron is much less than that for copper. This means that occurred nuclear reaction in iron sample is related to fast neutrons that has low cross section. This means that reactions related to fast neutrons have been occurred less than other neutrons. The reason for that is low cross section associated with fast neutrons that has been discussed completely in the paper.