Some Studies in Activation Foils for Measuring Low-Level Induced Activity for the Neutron Radiation Protection

For the measurement of induced activity in the activation foils, various methods and instruments are used. When the activity is measured by using a beta counter it is very important to know the beta attenuation in the activation foils. The beta attenuation in the foil depends on the beta spectrum of the activation product, the material and the thickness of the material. The beta attenuation has been evaluated theoretically as well as experimentally. The detailed investigations of beta attenuation in the foils are presented in this paper. The experimental study was conducted using an absolute system, the 4πβ-γ coincidence system. For the various foils like Au, Mn, Co, Al and Mg used in this study, it is found that both theoretical and experimental values for the beta attenuation are matching. The attenuation of betas in the foils varies with beta energy spectrum and the materials and it varies from 7% to 92%. The foil activation method is very accurate for the neutron fluence rate measurement. In foil activation method the induced activity is correlated to the neutron fluence rate. This activity is measured using different counters. 4πβ-Υ coincidence system is the primary standard for the activity measurement. If the activity is very low this system cannot be used for the measurement. 4πβ flow type proportional counters are used for the measurement of activity. For this the efficiency of the foil should be known accurately. Evaluation of the beta efficiency of different activation foils is discussed in this paper. Gold, Manganese and Cobalt foils are used for thermal neutrons and Magnesium and Aluminium foils are used for fast neutron measurements.