Abstract
Attenuation of the atomic-field bremsstrahlung, which is known as the external bremsstrahlung (EB), excited by Tl-204 and Tc-99 beta-emitters in Al, Cu, Cd and Pb targets has been studied. The beta stopper technique is employed to measure the integral intensities above 100 keV energy in different absorber thicknesses. The calculated values were obtained from the bremsstrahlung spectra recorded with different targets and the tabulated values of attenuation coefficients for mono-energetic gamma rays. A good agreement between the calculated and experimental results is obtained. It supports the correctness of the procedure used to obtain the attenuation of EB in metallic targets.