بررسی اثر نوع آشکارساز بر برآورد ضرایب انباشت پرتوهای گاما با استفاده از شبیه سازی مونت کارلو بر اساس کاهش واریانس

نویسندگان

دانشگاه صنعتی شاهرود

10.22052/6.4.65

چکیده

هدف از پژوهش حاضر بررسی تأثیر نوع آشکارساز در برآورد ضرایب انباشت پرتوهای گاما است. در این راستا، ضرایب انباشت شار پرتوهای گامای چشمه­ ی نقطه ­ای همسانگرد Co60 با انرژی متوسط MeV 253/1 در عبور از حفاظ­ های تیتانیوم، روی، تنگستن، و سرب با ضخامت­ های مختلف cm 5-1 توسط کد محاسباتی MCNPX مورد بررسی قرار گرفت. شار ذرات از طریق چهار نوع آشکارساز متداول برای اندازه گیری پرتوهای گاما در شبیه­ سازی برآورد شد: استوانه ­ی بدون ماده، شمارنده­ ی گایگر- مولر، سوسوزن سدیم یدید، و آشکارساز نقطه­ ای. با توجه به ضخامت زیاد مواد، از روش کاهش واریانس پنجره ­های وزنی در محاسبات استفاده شد تا علاوه بر کاهش زمان اجرای برنامه دقت نتایج را نیز افزایش دهد. در این پژوهش، وابستگی ضریب انباشت به عدد اتمی ماده، و نوع آشکارساز تعریف شده مورد تائید قرار گرفت و نتایج نشان داد در حالت­ های مختلف بررسی شده، مقادیر ضریب انباشت از 1 تا 4 متغیر است. با این حال، مسیر تغییرات ضرایب انباشت برای آشکارسازهای مختلف تقریبا یکسان بود. با توجه به این نتایج پیشنهاد می­ شود به منظور افزایش دقت شبیه ­سازی و کاهش زمان اجرای برنامه از آشکارساز نقطه ‏ای استفاده شود.

کلیدواژه‌ها


عنوان مقاله [English]

Study on effect of detector type in estimating buildup factor of gamma-rays by monte carlo simulation based on variance reduction

نویسندگان [English]

  • Hoda Alavian
  • Hossein Tavakoli-Anbaran
چکیده [English]

This paper presents the study on the effect of detector type in estimating gamma rays buildup factor. In this regard, the flux buildup factors of gamma rays emitted by an isotropic point 60Co source in mean energy 1.253 MeV was evaluated after passing through the Pb, W, Zn, and Ti sample in thickness of 1-5 cm by MCNPX. Four common detector types in simulation of measurement was defined to estimate the gamma rays flux: an empty cylinder, Geiger-Muller counter, NaI(Tl) scintillator, and point detector. Due to the deep penetration condition, weight windows varience reduction technique is applied to achieve more accuracy and less computer run time simultaneously. The present work confirm the buildup factor dependence on atomic number of materials, and detector type. The results show that the value of buildup factors was varied from 1 to 4 in different states. However, the variation of buildup factors follow almost similar trend in different detector types. According to the results, applying point detector in simulation is suggested which lead to increased accuracy of simulation and decreased computer run time.
 

کلیدواژه‌ها [English]

  • Buildup factor
  • Shielding
  • Detector type
  • Variance reduction
  • Monte Carlo simulation
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