使用飛行時間技術搭配閃爍體偵檢器被普遍用來量測中子能譜，針對實驗架設、參數設計和訊號處裡方法並無一標準程序，也鮮少文獻詳細記載所有實驗細節，而同在量測Cf-252的情況下，不同文獻之量測能譜波峰位置也不盡相同，表示各研究之量測系統能夠準確量測的最低能量限值需要討論，後續要利用此量測系統才能正確的量測能譜。若能夠有一個量測系統的參考標準，且了解能夠準確量測的能量範圍，將會是後續應用非常重要的基礎。本研究建立以飛行時間技術搭配閃爍體偵檢器的中子能譜量測系統，提供實驗架設，訊號處理之參考，此外透過探討影響能譜的兩項參數，光電倍增管高壓和閾值，了解此量測系統的最小量測限值。
本研究使用核能研究所標準實驗室的Cf-252中子射源進行量測，詳細記載實驗架設、參數設定及訊號處裡的過程和邏輯。在對訊號分別做了時間延遲修正、射源種類辨別、隨機訊號的處理和考慮閃爍體偵檢器的效率後，所得到的中子能譜和Cf-252的標準能譜Watt能譜比較，發現在大於2.4 MeV的範圍是準確的中子能譜。此外透調整高光電倍增管高壓和波形閾值發現，提高高壓和降低閾值皆可以降低系統的最低量測限值，但是提高高壓時會產生飽和訊號，導致高能中子的計數值降低，此情況下量測的能譜將失去準確性。經過實驗發現在光電倍增管1500 V和50 lsb的閾值設定下可以使本研究建立之量測系統有最低量測限值，約在1.4 MeV，即大於1.4 MeV之中子能譜具有參考性。
在使用中子能譜量測系統時，最重要的是如何進行量測和合理的訊號處裡，了解此量測系統能夠準確量測的能量範圍。本研究發展以TOF技術搭配閃爍體偵檢器之中子能譜量測系統，提供實驗架設和數據處裡的方法建議，且透過與標準能譜比較找出了此系統能夠準確量測中子能譜的能量範圍，對後續的應用奠定基礎。

Time-of-Flight (TOF) technique and scintillator detector are regularly used in neutron spectrum detection, but there is no standard process, and only few studies show the detail of experiment parameters. Also, for the studies which measure 252-Cf neutron source, all comes out with different peak energy, that means the system’s reliable measure range should be discussed, or that might be the potential problem in application.
We use Cf-252 neutron source in INER to do the experiment, provide all the details including experiment setup, parameters, process and logic of data analysis. We revised the time delay, separated different radiation source, subtracted random scattering and consider the detection efficiency to get the neutron spectrum. After the comparison with Watt spectrum, we found that neutron spectrum is reliable for energy more than 2.4 MeV. By adjusting PMT high voltage and threshold, we found that higher PMT high voltage and lower threshold can make the energy limitation of the detection system lower. However, higher PMT voltage will generate more saturation signals, it will cause the loss of high energy neutron counts. The detection system can have lowest measure limitation, 1.4 MeV, under 1500 V high voltage and 50 lsb threshold.
The most important thing when measure the neutron spectrum is how to setup and analysis data in the right way. We developed the neutron spectrum detection system with TOF technique and scintillator detector, provide the standard way to setup the experiment and analysis data, find out the reliable measure energy range for application.

目錄
摘要 i
Abstract ii
致謝 iii
目錄 iv
表目錄 vii
圖目錄 viii
第一章 緒論 1
1.1 研究目的及動機 1
1.2 研究方法與步驟 1
1.3 名詞解釋 2
第二章 介紹與文獻回顧 5
2.1 Cf-252中子射源 5
2.2 Time-of-Flight (TOF) 6
2.3 閃爍體偵檢器與其作用原理 7
2.4 脈波形狀鑑別法 (Pulse Shape Discrimination, PSD) 10
2.5 閃爍體偵檢器搭配TOF的中子量測 12
第三章 研究設計與方法 14
3.1 TOF實驗架設 14
3.2 時間延遲修正 18
3.3 光子與中子的鑑別 20
3.3.1 閃爍體偵檢器的脈波形狀鑑別法和數位轉化器 20
3.3.2 PSD範圍選擇和Fiducial cut 23
3.3.3 TOF spectrum 25
3.4 隨機散射訊號扣除 25
3.5 飛行時間與能量轉換 27
3.6 偵檢器固有效率模擬 28
3.6.1 光產率分布 28
3.6.2 閾值計算 30
3.6.3 計算偵檢效率 32
3.7 TOF 實驗參數的影響及最小量測能量 32
第四章 結果與討論 34
4.1 TOF spectrum 34
4.2 時間延遲的計算結果 35
4.3 PSD 分布及使用fiducial cut挑選的PSD範圍 36
4.4 隨機散射訊號的扣除 39
4.5 經過飛行時間與能量轉換的中子能譜 39
4.6 偵檢器固有效率模擬 40
4.6.1 回跳質子沉積能量分布 40
4.6.2 量測系統的閾值 41
4.6.3 設定閾值後得到的偵檢器固有效率 42
4.7 Cf-252能譜 44
4.8 光電倍增管高壓和閾值對量測系統的影響 46
4.8.1 光電倍增管高壓對量測系統的影響 46
4.8.2 閾值對量測系統的影響 49
4.8.3 量測系統極值 51
第五章 結論與未來工作 53
5.1 研究結論 53
5.2 未來工作 53
參考資料 54
附錄 57
I. 第一部份的實驗參數(包括CoMPASS 軟體設定) 57
 

[1] S. Agosteo, P. Colautti, J. Esposito, A. Fazzi, M. V. Introini, and A. Pola, “Characterization of the energy distribution of neutrons generated by 5 MeV protons on a thick beryllium target at different emission angles,” Appl. Radiat. Isot., vol. 69, no. 12, pp. 1664–1667, 2011.
[2] Y. Iwamoto et al., “Characterization of high-energy quasi-monoenergetic neutron energy spectra and ambient dose equivalents of 80-389 MeV 7Li(p,n) reactions using a time-of-flight method,” Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrom. Dect. Assoc. Equ., vol. 804, pp. 50–58, 2015.
[3] R. A. Livingston, H. H. Saleh, R. C. Block, and P. J. Brand, “Time-of-flight calibration of a 6Li glass epithermal neutron detector,” Appl. Radiat. Isot., vol. 53, no. 4–5, pp. 773–777, 2000.
[4] H. N. Field, M. Hagiwara, Y. Unno, J. Nishiyama, M. Yoshizawa, and H. Seito, “Time-of-Flight Measurements for Low-Energy Components of 45-MeV Quasi-Monoenergetic Reaction,” IEEE Trans. Nucl. Sci., vol. 62, no. 3, pp. 1295–1301, 2015.
[5] M. Tessler et al., “Neutron Energy Spectra and Yields from the 7Li(p,n) Reaction for Nuclear Astrophysics,” J. Phys., vol. 665, no. 1, 2016.
[6] A. J. Kreiner et al., “Present status of Accelerator-Based BNCT,” Re. Pract. Oncol. Radiother., vol. 21, no. 2, pp. 95–101, 2016.
[7] H. W. Koay, T. Shima, M. Fukuda, H. Kanda, S. Hara, and T. Yorita, “Experimental study of fast-neutron production and moderation for accelerator-based BNCT system,” Appl. Radiat. Isot., vol. 152, no. May, pp. 11–17, 2019.
[8] M. G.Paff et al., “Gamma/neutron time-correlation for special nuclear material detection - Active stimulation of highly enriched uranium,” Ann. Nucl. Energy, vol. 72, pp. 358–366, 2014.
[9] Y. Iwamoto et al., “Characterization of quasi-monoenergetic neutron source using 137, 200, 246 and 389 MeV 7Li(p,n) reactions,” Prog. Nucl. Sci. Technol., vol. 4, pp. 657–660, 2014.
[10] G. Feinberg et al., “Quasi-stellar neutrons from the 7Li(p,n)7Be reaction with an energy-broadened proton beam,” Phys. Rev. C - Nucl. Phys., vol. 85, no. 5, pp. 1–12, 2012.
[11] V. V. Desai, B. K. Nayak, A. Saxena, S. V. Suryanarayana, and R. Capote, “Prompt fission neutron spectra in fast-neutron-induced fission of 238U,” Phys. Rev. C - Nucl. Phys., vol. 92, no. 1, pp. 1–8, 2015.
[12] A. J. Grievson, “Time-of-flight spectrometry of the spontaneous fission neutron emission from 244Cm and 252Cf using EJ-309 liquid scintillators,” PhD thesis, Lancaster University, 2020.
[13] J. Verbeke, C. Hagmann, and D. M. Wright, “Simulation of Neutron and Gamma Ray Emission from Fission,” Laurence Livemore National Laloratory, Livemore CA Tech. Rep. UCRL-AR-228515, 2007.
[14] T.Aoki et al., “Measurement of differential thick-target neutron yields of C, Al, Ta, W(p, xn) reactions for 50-MeV protons,” Nucl. Sci. Eng., vol. 146, no. 2, pp. 200–208, 2004.
[15] G. F. Knoll, Radiation Detection and Measurement, 4th Edition, Willey, 2010
[16] A. Enqvist, C. C. Lawrence, B. M. Wieger, S. A. Pozzi, and T. N. Massey, “Neutron light output response and resolution functions in EJ-309 liquid scintillation detectors,” Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrometers, Detect. Assoc. Equip., vol. 715, pp. 79–86, 2013.
[17] L. Stevanato, D. Cester, G. Nebbia, and G. Viesti, “Neutron detection in a high gamma-ray background with EJ-301 and EJ-309 liquid scintillators,” Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrometers, Detect. Assoc. Equip., vol. 690, pp. 96–101, 2012.
[18] F. D. Becchetti, M. Febbraro, R. Torres-Isea, M. Ojaruega, and L. Baum, “252Cf fission-neutron spectrum using a simplified time-of-flight setup: An advanced teaching laboratory experiment ,” Am. J. Phys., vol. 81, no. 2, pp. 112–119, 2013.
[19] L. Cheol Ho, S. Jaebum, K. Tae Hoon, L. Sangmin, and K.Yong-Kyun, “Measurement of Neutron Energy Spectrum Emitted by Cf-252 Source Using Time-of-Flight Method,” Transactions of the Korea Nuclear Society Autumn Meeting, pp. 27–28, 2016.
[20] CAEN staff, User Manual UM5960 CoMPASS, CAEN, 2021.
[21] F. Pino, L. Stevanato, D. Cester, G. Nebbia, L. Sajo-Bohus, and G. Viesti, “The light output and the detection efficiency of the liquid scintillator EJ-309,” Appl. Radiat. Isot., vol. 89, pp. 79–84, 2014.
[22] P. Prusachenko, I. Bondarenko, V. Ketlerov, V. Khryachkov, and V. Poryvaev, “Digital spectrometer for prompt fission neutron spectrum measurements,” EPJ Web Conf., vol. 146, 2017.
[23] H. Shahabinejad and M. Sohrabpour, “A novel neutron energy spectrum unfolding code using particle swarm optimization,” Radiat. Phys. Chem., vol. 136, no. March, pp. 9–16, 2017.