為了增進在清華開放式水池反應器(THOR)硼中子捕獲治療(BNCT)設施的中子能譜測量精準度，本研究將傳統的中子活化偵檢器測量法做進一步改良，將傳統的裸活化箔片嵌在球型緩速體及吸收體中，有三項優點：(1)可減少中子射源的角分布對偵檢器的影響；(2)利用緩速體及吸收體來改變球心的箔片對中子的響應，可產生多種能涵蓋不同能量範圍的響應函數；(3)使用球型偵檢器可以改善箔片對超熱中子的偵測效率，減少整體實驗量測的時間，有利於精進能譜測量的結果。
本研究會介紹這種新型的球型中子活化偵檢器，偵檢器的響應函數計算以及利用SAND-Ⅱ能譜演算法為主的能譜反解程式SAND-EX。對於球型活化檢器的測量效果，會先以理論測試來評估能譜反解的結果，並實際在THOR BNCT設施進行實驗量測，傳統的裸活化箔片會做為反解結果比較的基準，不論理論或實驗，結果都證明使用球型偵檢器能有效改善中子能譜測量結果。
本研究會探討反解參數不同對反解結果的影響，包含使用不同初始能譜對反解結果影響，射源的角分布不同對偵檢器響應函數的影響，還有在活化箔片中加入包覆鎘片的活化箔片對反解結果的影響，另外本研究也利用MAXED反解程式以探討使用不同的反解演算法的結果。總結上述反解參數的靈敏度影響的結果，在BNCT中子能譜測量上，球型偵檢器還是比傳統的活化箔片能得到較穩定較好的結果。

A set of spherical-type activation detectors was developed aiming to provide better determination of the neutron spectrum at the Tsing Hua Open-pool Reactor (THOR) BNCT facility. The activation foil embedded in a spherically shaped holder exhibits three advantages: (1) minimizing the effect of neutron angular dependence, (2) creating response functions with broadened coverage of neutron energies by introducing additional moderators or absorbers to the central activation foil, and (3) reducing overall detection time by increasing efficiencies of most activation foils under the irradiation of epithermal neutrons. This paper presents the design concept and the calculated response functions of new detectors. Theoretical and experimental demonstrations of the performance of the detectors are provided through comparisons of the unfolded neutron spectra determined using this method and conventional multiple-foil activation techniques.

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