الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
For each isotope, there are a number of permitted transitions inside the nucleus between different energy levels with definite probabilities and number of gamma rays emitted in these transitions with energies equal to the difference between the two levels that the transition has been happened between them. The isotopes emit different gamma rays energies but the ratio between the intensities of these energy peaks (photon energies) is constant and depends on the probabilities of the transitions inside the isotopes. So the isotopes can be known from the energy peaks and the ratio between their intensities. The detection technique can be used to measuring these intensities N or the counting number of the detector with measuring time T and the probability of emission P_r are exactly known. The radionuclide activity, A, and its detector efficiency,
There are a large number of possible interaction mechanisms for gamma rays in matter, The probability of which interaction will go on is identified from the intensity of the gamma rays energy and the cross section of the results of the interactions can be identified by the gamma-ray’s spectrum and the initial flux. So, the exact definition of gamma-ray’s spectrum is necessary for its valuable applications. This is obtained by having an accurate detection and recording method [1],[ 4].