• 作者： 馬步原
• 作者服務機構： 國立清華大學
• 中文摘要： 中子在氫，氘，輕水，重水，石墨及糖中之減能時間，用蒙特卡羅法求取。為便於運算，寫製完成一計算機算碼（Computer code）取名SDT（Slowing down time）。計算中，用到有關物質各元素對各種能量中子之截面積，其非彈性撞擊之特性也按實情考慮無遺。為求中子在水，和重水中之減能時間，曾各研讀10,000個中子由分裂產生至熱化的經歷，為研究氫氣，氘氣，石墨及蔗糖，則各研讀1,000個中子在其中之經歷，並將各中子之減能時間，及過程中所經碰撞之次數，均詳加記錄，由計算機作成其分佈明細表，根據此表繪製統計圖（Histograms）示其分佈狀況。平均之減能時間，與平均碰撞數，也另以均值算法求出，兩者此較，知物質中倘有較輕元素存在時，由蒙特卡羅法求得之數值常比均值法求得者略大。反之，在石墨中，兩者全等。
• 英文摘要： Neutron slowing down time in hydrogen, deuterium, water, heavy water, graphite,and sugar were determined by the Monte Carlo method. A digital computer programSDT was specially written for this purpose. In SDT program, energy dependentcross-sections are used in calculations, and the inelastic properties are also considered.10,000 histories each were generated for water, and heavy water, 1,000 histories eachwere generated for hydrogen, deuterium, graphite, and sugar to study the slowingdown times for neutrons from fission to thermalization. The distributions of thenumber of collisions in the slowing down process were also recorded and are dis-played in histograms. The average slowing down time and the average number ofcollisions are checked by the results from the energy-dependent mean value method.It indicates that for hydrogeneous moderators, the values got from the Monte Carlomethod are slightly greater than those from the mean value method, but they areexectly same for graphite.
• 中文關鍵字： --
• 英文關鍵字： --