- 學位論文
使用傳統與延長能量範圍波納球體能譜偵檢器評估中子能譜的比較
Comparison of the Evaluated Neutron Spectra between the Methods of Traditional and Extended-Range Bonner Spheres
摘要
現今高能輻射粒子逐漸被使用於放射治療，為了評估高能輻射粒子伴隨產生中子能量與通量的分佈，波納球體能譜測量儀（簡稱BSS）是國際上最常用來評估中子能譜的儀器；但卻不適用於超過10 MeV以上高能中子的量測。在傳統的BSS加上一層高原子序物質如鉛、銅，可以提升(n, xn)反應機率，進而提升在高能量響應函數的數值，這種系統稱之為延長能量範圍波納球體能譜測量儀（簡稱ERBSS）。 本研究使用七種尺寸BSS與自製的四種含鉛球殼與聚乙烯球殼的ERBSS搭配金箔測量標準射源Cf-252與清華開放式水池反應器（簡稱THOR）的中子能譜，並比較在Cf-252與THOR中使用BSS與ERBSS所得到能譜的差別。 從結果可以清楚發現，在國際標準射源Cf-252與THOR的實驗中，傳統BSS搭配ERBSS的中子能譜結果與傳統BSS的中子能譜結果是相似的，可以證明本研究所自製的ERBSS可以使用於中子能譜量測。可以觀察到當傳統BSS搭配PbPE球殼可以使能譜更符合真實能譜，所以當球組的數量增加，可以提高電腦軟體UMG 3.3計算中子能譜的準確度。未來待國內高能中子設施建置完成並開始運轉，可再利用此研究自製的ERBSS系統進行高能中子能譜評估與分析。
並列摘要
Nowadays, high-energy radiation particles are used in radiation therapy gradually. High-energy radiation particles always accompany with high-energy neutrons. To evaluate the distributions of neutron energies and fluences, the Bonner Sphere Spectrometer (BSS) is most commonly used to assess the neutron spectrum in international, but it is not good when particle energy exceed 10 MeV. High atomic number materials like lead, or copper is added to traditional BSS to increase (n, xn) cross-section, and then enhance the magnitude of the response functions in high energies. This new detection system is called Extended-Range Bonner Sphere Spectrometer (ERBSS). In this research, 7 different sizes BSS and self-made ERBSS including 2 lead sphere-shells and 2 polyethylene sphere-shells with gold foil were used to measure neutron spectra of standard neutron source Cf-252 and Tsing-Hua Open-pool Reactor (THOR). The neutron spectra of Cf-252 and THOR measured by means of traditional BSS and ERBSS were compared. The results showed that the neutron spectra of ERBSS and traditional BSS are similar in measuring standard Cf-252 source and THOR, and the ability of self-made ERBSS measuring neutron spectra was verified and proved. The results also showed that traditional BSS accompany with PbPE sphere-shell is more fit to real neutron spectrum. It can increase the calculation accuracy of program UMG 3.3, which calculate the neutron spectrum, when the sphere set is increased. The high-energy neutron facilities are going to be constructed and operated in the future, in Taiwan. By experimental verification of this study, the feasibility of using self-made ERBSS system to evaluate and analysis high-energy neutron spectrum is approved.