Abstract

Neutron beam diameter is a very important parameter in the experimental nuclear research. Determination of the correct neutron beam diameter is the best method to prepare corectly the optimal sample size correctly, reduced data analysis errors. To measure the neutron diameter, some methods were used: Simulation by Monte – Carlo method, neutron image, and neutron activation analysis. In this report, we determined the neutron beam diameter of the 3rd horizontal channel of the Dalat nuclear reactor that activated gold foils. The result shows that this method offer quick and more correct results than other methods which had been published preiously [1, 2].