الفهرس 
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Abstract
This thesis studies and discusses all the factors effecting on the determination of the detector full-energy peak efficiency such as, the source self-absorption coefficient in case of volumetric sourcesand the coincidence summing effect at different source-to-detector distances. The coincidence correction factors have been calculated using three radionuclides 60Co, 133Ba and 152Eu. The experimental values of thefull-energy peak efficiency (FEPE) have been corrected for two different gamma-ray detectors, NaI(Tl) scintillation detector and HPGe semiconductor detector. The numerical simulation method (NSM), ETNA program and EFFTRAN software were used to calculate the coincidence summing correction factors as well. The thesis contains six chapters, (121) references, three appendices, plus English and Arabic summaries.
The First Chapter:
This chapter introduces a general introduction about the gamma-rays spectrometry, applications, studying the different factors affectingon the detection efficiency, especially the coincidence summing effect. Literature review on the previous works beside the aim of the work has been presented at the end of this chapter.
The Second Chapter:
This chapter is devoted to putting forward definitions and explanations of the different detection efficiencies. Experimental, Empirical, Monte Carlo, Direct Mathematical and the Efficiency Transfer Methods have been discussed in details. Commercial software like ETNA program and EFFTRAN software were discussed as an application on the efficiency transfer method. Using these software the full-energy peak efficiency can be calculated, also the coincidence summing correction (CSC) factors can be easily determined, then used to correct the measured efficiencies.
The Third Chapter:
In this chapter, the effective solid angle between the radioactive point and cylindrical shape sources, with respect to NaI(Tl) and HPGe coaxial detectors has been calculated, depending on the direct mathematical method. The source self-absorption coefficient has been taken in to account in case of volume sources to achieve a valid efficiency values. A new numerical simulation method to calculate the coincidence summing correction factors was introduced for 60Co, 133Ba and 152Eu radionuclides.
The Fourth Chapter:
This chapterdescribes the calibration process of gamma-rays detectors that have been used. The experimental technique was performed at Prof. Dr. Younis. S. Selim laboratory for Radiation Physics, Alexandria University, Egypt. Moreover, this chapter contains a detailed description of all radioactive sources that have been used in this work (Point and Cylindrical sources). A brief description for using the collecting spectrum software “WinTMCA32”, that has been made by ICx Technologies, beside the “Genie 2000” data acquisition and analysis software made by Canberra were discussed.
The Fifth Chapter:
The full-energy peak efficiency was calculated using the efficiency transfer principle, also the total efficiency were obtained as presented in chapter three using the direct mathematical method. The calculated full-energy peak efficiency and total Efficiency values were used to calculate the coincidence summing correction factors (CSC) by the numerical simulation method (NSM) for 60Co, 133Ba and 152Eu nuclides depending on the coincidence summing model presented as well in chapter three. ETNA program and EFFTRAN software were used to obtain a coincidence summing correction factors (CSC) at all the measurement geometry. A comparison between these three correction factors was imported. In addition, a comparison between the measured efficiency before and after correction by NSM, ETNA and EFFTRAN were introduced. Remarkably good agreements were clearly noticed between the obtained efficiencies.
The Sixth Chapter:
This chapter includes the conclusions drawn out of the presented work.
Appendices
The first Appendix (A) contains the Sum of probabilities of the transitions between all energy levels for 133Ba and 152Eu radionuclides, the second appendix (B) contains all energies of 152Eu radionuclide and its gamma transition (starting and arrival levels). The third appendix (C) contains the list of publications extra.