大氣層次級宇宙射線蒙地卡羅模擬及飛航劑量評估

大氣層次級宇宙射線主要由銀河宇宙射線與空氣組成原子撞擊所產生，其強度隨高度、位置與時間變化。次級宇宙射線在地表對人類具有一定的劑量貢獻，若在飛航高度上，其劑量貢獻更是不容小覷。由於大氣層次級宇宙射線輻射場極為複雜，輻射粒子種類多而且能量範圍極廣，不易單靠實驗進行定量分析，本研究利用蒙地卡羅方法進行詳細的模擬，建立一組大氣層次級宇宙射線劑量隨高度、位置與時間變化的資料庫，可以快速準確地評估地球表面大氣層內任何位置之宇宙射線各成分的輻射劑量。為了探討次級宇宙射線在大氣層中的分布特性，本研究採用內建有宇宙射線計算模組的FLUKA蒙地卡羅程式，考慮宇宙射線隨位置與時間變化共計44個模擬案例，計算結果彙整以不同高度下有效劑量率隨垂直截止剛度變化關係進行擬合與內插，建立大氣層內三維次級宇宙射線劑量資料庫與評估模型，並通過一系列驗證確認其正確性。本研究建立的資料庫與評估模型具有廣泛潛在的用途，例如可以快速準確地評估任何飛航劑量。首先著重在台灣相關的重要航線，本研究評估台灣飛往紐約、洛杉磯、法蘭克福、阿姆斯特丹、雪梨、東京、新加坡、杜拜、北京、香港及金門等11條常見航線的有效劑量詳細資訊，包括次級宇宙射線各成分的即時劑量率與累積劑量，研究結果除了有利於宇宙射線相關研究參考之外，更提供國內管制單位與一般民眾關於背景輻射的重要資訊。

關鍵字

宇宙射線二次輻射；飛航劑量；蒙地卡羅； FLUKA

並列摘要

Secondary cosmic radiation in atmosphere is generated by interaction of primary galactic cosmic radiation with the constituents of air. Humans at sea level receive certain dose exposure from secondary cosmic radiation, if at flight altitudes or mountains, the dose contribution becomes much higher. Because of the complexity of secondary cosmic radiation, measurement alone is not enough to provide details of the radiation field. Based on the results of a series of Monte Carlo simulations, this study established a rather complete database of secondary cosmic radiation in atmosphere considering the effective dose variations of each components as functions of altitude, location, and time. The FLUKA Monte Carlo transport code was used to study the characteristics of secondary cosmic radiation in atmosphere. In total, 44 simulation cases were carried out in this study. The simulation results were benchmarked, analyzed and summarized in a database by applying curve fitting for effective dose rates at various altitudes and vertical cut-off rigidities for the two extremes of the sun's 11-year activity cycle. The database established in this study could have many potential applications. One example is to quickly and accurately estimate the dose exposure for any flight route. Focusing on those popular flights in Taiwan, this study estimated the aviation doses for the following flight routes from Taiwan to New York, Los Angeles, Frankfurt, Amsterdam, Sydney, Tokyo, Singapore, Dubai, Beijing, Hong Kong and Kinmen. The models and results presented in this study could not only be beneficial for those cosmic-ray related studies but also provide useful dada about natural background radiation for regulatory agencies and general public in Taiwan.

並列關鍵字

Cosmic-ray induced radiation ； aviation dose ； Monte Carlo ； FLUKA

參考文獻

[1] D. O’Sullivan, “Evaluation of the Cosmic Radiation Exposure of Aircraft Crew”, DOSMAX Report, 2000

[2] M. DURANTE, “Biological dosimetry in astronauts”, Rivista Del Nuovocimento, vol. 19, pp. 12, 1996

[4] A.K. Singh, Devendraa Siingh, R.P. Singh, “Impact of galactic cosmic rays on Earth’s atmosphere and human health”, Atmospheric Environment, vol. 45, pp. 3806-3818, 2011

[6] W. Friedberg et al., “Cosmic Radiation and Aircrew Exposure”, Nuclear Technology Publishing, pp. 323–328, 2000

[8] Goldhagen P, “Measurement of the energy spectrum of cosmic-ray induced neutrons aboard an ER-2 high-altitude airplane”, Nucl Instrum Methods Phys Res A. 1, vol. 476, pp. 42-51, 2002

國際替代計量

大氣層次級宇宙射線蒙地卡羅模擬及飛航劑量評估

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