- 期刊
輻射粒子用EXCEL以蒙地卡羅法追蹤軌跡
Simulating the Radiation Particle Transport by the Monte Carlo Method with EXECL Soft-ware
摘要
本文利用Excel程式以蒙地卡羅方法進行輻射粒子遷移的模擬。文中以追蹤點射源射出之粒子爲主軸，並以較簡單的二維平面取代實際狀況的三度空間，再假設粒子在飛行過程中，不會因被吸收而無法繼續飛行，另外粒子飛行一特定距離後一定會發生碰撞，且碰撞後只能有八個特定的方向中隨機取當中的一個方向，繼續追蹤，直到走完一萬步再分析觀察，以得到結果。經過在Excel畫面填入追蹤相關的數據及函數，連跑後每一粒子所出現的軌跡均不相同，充分顯示蒙地卡羅隨機取樣的真正行爲。又將所有十三顆粒子模擬的結果相互重疊，結果出現了粒子碰撞點的分佈圖類似變形的世界地圖，而非所期望的，粒子碰撞點的分佈圖應會出現 一個以(0, 0)爲圓心的密實圓形分佈，這又驗證了使用蒙地卡羅模擬追蹤時，如果取的樣本數不足時，則其結果很可能會四不像。
並列摘要
The transport of the radiation particle is simulated by the Monte Carlo method with EXECL software. The key point of this paper is to trace a radiation particle ejected from a point source. Instead of tracing the particle in a 3-dimensional coordinate, a simpler 2 -dimensional coordinate is used. It is assumed that particle can not be absorbed during their transportation. After flight a fixed distance; call one step, the particle is forced to collide with the medium, and then is scattered out randomly in one of the eight specified directions. After 10000 steps tracing the behavior of the particle is observed and analyzed.The EXECL software is treated as a computer code to run the Monte Carlo simulation of particles. The data and the mathematical functions are put in the EXECL table. After 13 cases running the trajectories of these particles are quite different. It shows the true behavior of the Monte Carlo random sampling.Overlap the tracing results of these 13 particles, the collision points distribution of these 13 particles shows as a distorted map of the world. The expected collision points distribution is as a concentrated dot point distribution in a circle with the center located at the center (0,0). It also shows if the sample size of the random sampling is not large enough the result of the simulation will become meaningless.