5319

4989

كارشناسي ارشد

فيزيك

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1388

ده،113ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

محمد حسن علامت ساز

احمد شيراني

13/4/89

اكبر پروازيان ،ظفرالله كلانتري

فيزيك

ID4989

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

A New Formula For Calculating Gamma Ray Exposure Buildup Factor in Double Layer Shields Water And Lead using MCNP Code And MINUIT Code Maryam alsadat Mohseni m mohseni@ph iut ac ir Date of Submission 2010 01 25 Department of physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Persian Supervisor Mohammad Hasan Alamatsaz alamatsa@cc iut ac ir Abstract Buildup factors are important data in radiation shielding which correct the response to uncollided photons so as to include the contribution of the scattered photons and secondary sources It is very important to know buildup factors for various materials and their combinations which are usually used for radiation shielding In this thesis first we computed gamma ray exposure buildup factors using the MCNP code Monte Carlo N Particle code System In the MCNP model a point monoenergitic isotropic source with energy from 0 3 to 10 MeV was placed at the center of the first spherical material surrounded by a second one The first shielding material was water and the second one was lead The total thickness of the shield varied between 2 to 10 mfp As well as primary interactions such as photoelectric effect Compton scattering and pair production we considered effect of bremsstrahlung and coherent Rayleigh scattering Then the MCNP computed data were analysed by plotting the buildup factor as a function of each independent variable energy first material thickness and second material thickness and observing the trends Based on the trends we tested many different expressions with different number of constants By MINUIT the fortran code the constants were calculated which give the best agreement between the MCNP computed exposure buildup factor and that obtained by formula Trying on many expressions at last we developed a polynomial formula with 11 constants that reproduce exposure buildup factors for two layer shields consisting water and lead with relative error and compared with the MCNP results below 2 Keywords Gamma ray Layer of Water Layer of Lead Exposure Biuldup factor MCNP code MINUIT the fortran code

محمد حسن علامت ساز

احمد شيراني

اكبر پروازيان ،ظفرالله كلانتري