4572

4300

كارشناسي ارشد

فيزيك هسته اي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1387

نه، 105، [II] ص: نمودار، جدول

ص. ع. به: فارسي وانگليسي

محمدحسن علامت ساز

احمد شيراني

88/4/31

ظفراله كلانتري ، اكبر پروازيان

1396/09/12

كتابنامه

فيزيك

ID4300

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

The calculation of gamma ray exposure buildup factors for plane source in monolayer and two layer lead and water shields with MCNP code including the effects of coherent scattering Student name Mojtaba Mokari Behbahani Email address m mokari@ph iut ac ir Date of submission February 9 2009 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Mohamad Hasan Alamatsaz alamatsa@cc iut ac irAbstractThe exposure buildup factors EBFs have so far been calculated by computer simulations for pointsources with spherical shields considering the effect of coherent scattering and with plane sources andstratified slab shields without effect of coherent scattering In this thesis the MCNP code Monte Carlo N particle is utilized to calculate the EBFs for normal planesources in an absorbent monolayer and two layer environment of water and lead Then the effect of thecoherent scattering and fluorescence radiation are investigated First we will obtain the EBFs for energiesrange of 0 5 6 MeV under the geometrical conditions of the previous studies without coherent scatteringeffect Then considering importance of EBFs we calculate them by taking into account all factors forrange of energy of 0 1 6 MeV All calculations of EBFs are done for monolayer and two layerenvironments EBFS without coherent scattering are different in a single layer of water or lead as a lowand a high atomic number environment respectively EBFs increase as energy of incident photondecreases or thickness slab shield increases Coherent scattering decreases the number of uncollided andincreases the total number of photons reaching the detector and as a result EBFs are increased Thiseffect is observed stronger in higher energies and weaker in lower energies According to the MCNPresults the coherent scattering effect in water is not considerable for the energies above 3 MeV and inlead is considerable for the energies up to 6 MeV Along with the coherent scattering effect thefluorescence radiations effects on the EBFs were investigated The fluorescence radiations effect occursin energies above 88 keV in lead There are some considerable effects of the fluorescence radiations onEBFs in massive elements like lead below 200 keV energy If the gamma ray energy is more than 88keV for 78 8 of photoelectric interactions in lead an electron will be ejected from K layer and afluorescence x ray with 78 53 keV energy is produced These radiations are emitted homogeneously For0 1 MeV gamma ray due to the production of secondary photons in the range of energy of the incidentphotons EBFs are not increased as one expects So the increase in EBFs due to the coherent scattering isconsiderably slowed down because of the fluorescence radiation Kay words MCNP exposure buildup factor gamma ray coherent scattering florescence radiation

محمدحسن علامت ساز

احمد شيراني

ظفراله كلانتري ، اكبر پروازيان