TLD量測技術之改進用以執行BNCT射束品保測量｜國立清華大學博碩士論文庫

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研究生：	蔡文旗 Tsai, Wen-Chyi
論文名稱：	TLD量測技術之改進用以執行BNCT射束品保測量 Improvement of TLD Measurement Technique Aiming for QA Measurement of BNCT Beam
指導教授：	江祥輝 JIANG, SHIANG-HUEI
口試委員:	林威廷許榮鈞袁明程洪明崎
學位類別：	博士 Doctor
系所名稱：	原子科學院 - 工程與系統科學系 Department of Engineering and System Science
論文出版年：	2017
畢業學年度：	105
語文別：	英文
論文頁數：	70
中文關鍵詞：	熱發光劑量計、品保測量、回火、衰減係數、校正因子
外文關鍵詞：	TLD, QA measurement, Annealing, Attenuation Coefficient, Calibration Factor
相關次數：	點閱：4 下載：0
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本博士論文首先探討TLD測量技術之回火和計讀過程。我們用實驗證明廠商建議的LiF:Mg,Cu,P TLD置於回火盤上放入烤箱回火效果不佳，原因是回火盤上達到的溫度遠低於烤箱預設溫度。因此，我們設計了一個加熱板，能夠準確控制在加熱板上的回火盤的溫度，採用薄(2 mm)回火盤置於加熱板上，以240℃/10 min回火，可將TLD-700H, TLD-7000和TLD-2007之殘留訊號降至0.2%。若搭配最佳化之計讀程序則可使10次測量的再現性達到~0.36%。以此回火技術研究之成果為基礎，我們建立了一個最佳化回火計讀程序，接下來的研究即採用此一最佳化回火計讀程序進行。

本博士論文的主題是利用TLD-400 (CaF2:Mn)從事BNCT射束加馬射線劑量和中子活化品保測量。由於TLD-400對中子的靈敏度非常低，所以我們採用TLD-400薄片置於一個立方形PMMA (壓克力)假體內，讓BNCT射束由假體一面入射進來，用以測量假體內加馬射線劑量。既然TLD-400薄片含有適當含量的Mn活性劑，因此在本研究中我們也同時採用它來做中子活化測量。在本研究中我們也首度提出利用中子誘發56Mn活度衰變造成的自照射熱發光(TL)訊號來做TLD-400薄片的現場校正。過程中56Mn活度係利用高純鍺(HPGe)偵檢器測量，而每次56Mn衰變造成的能量積存則利用MCNPX模擬計算獲得。

接著我們繼續努力進一步改善測量不準度並使測量程序變得更容易方便。我們將每一顆TLD-400薄片當作一個個別偵檢器來使用，每顆都有編號及指定方位，同時利用各種實驗室小射源與TLD-400薄片直接緊貼來執行現場校正。我們利用一個簡化的衰減模型搭配MCNPX程式模擬計算的薄片內能量積存隨厚度之分佈來測定熱發光在測量路徑上之衰減效應。由於TLD薄片內能量積存隨厚度分佈非常不均勻，我們也以實驗證明，我們所提議的現場校正方法要能可用且有效，熱發光衰減之修正扮演一個關鍵的角色。

在計讀經BNCT射束照射過的TLD-400薄片的過程中，我們意外發現由於薄片中受中子照射誘發產生的56Mn活度會使TLD-400薄片持續放出顯著的閃爍光(SC)，如同一般無機閃爍體一樣。因此我們也探討TLD-400的閃爍特性，意圖開發TLD-400的額外閃爍應用。首先我們粗略測試我們實驗室擁有的各型TLD發射閃爍光的效率。TLD-400發射的閃爍光強度確實較其他類型TLD強10倍甚至到100倍。利用TLD計讀機不需加熱計讀的閃爍光經由校正後，可用來測量經BNCT射束照射後之TLD-400薄片中的56Mn活度。我們也利用一個簡化的閃爍光衰減模型來探討閃爍光在TLD-400中的衰減。最後我們也利用TLD-400發射的閃爍光來測量緊貼接觸的實驗室小射源的活度。

This Ph.D. work started from the study of the annealing and readout process of the TLD measurement technique. The ineffectiveness of the oven annealing for the LiF:Mg,Cu,P thermoluminescent dosimeter with a thick annealing tray was demonstrated to be due to the fact that the temperature achieved on the annealing tray was significantly lower than the oven preset temperature. The 240 oC / 10 min annealing using a special-designed hot plate, for which the heating temperature on the thin annealing tray can be accurately controlled, has been presented to be capable to reduce the residual signal of the TLD-700H, TLD-7000, and TLD-2007 detectors to less than 0.02% and achieve a reproducibility for 10-cycle measurements of ~0.36% when an optimal readout cycle has been applied. Based on the achievement of the annealing technique study we established an optimum annealing and readout process.

The theme of this work is the QA measurement of gamma-ray dose and neutron activation using TLD-400 for BNCT beam. TLD-400 (CaF2:Mn) chips were applied for the gamma-ray dose measurement in a PMMA phantom exposed to a BNCT beam because of their very low neutron sensitivity. Since TLD-400 chips possess an adequate amount of Mn activator they have been employed in this work simultaneously for neuron activation measurement. The self-irradiation TL signals owing to the decay of the neutron induced 56Mn activity have been applied for a calibration of the TLD-400 chip in situ, where the activities were measured by an HPGe detector system and the energy deposition per disintegration of 56Mn was calculated by applying a Monte Carlo code.

An effort has been made to improve the measurement uncertainty furthermore and facilitate the measurement process. Each TLD-400 chip was treated as an individual detector with a given ID number and denoted orientation and an in situ calibration of the TLD chip by using small laboratory sources in direct contact with the TLD chips was proposed. The attenuation effect of the TL light has been determined by using a simplified attenuation model in couple with the energy deposition distribution acquired from Monte Carlo code simulations. Since the energy deposition distribution is highly non-uniform, it has been demonstrated that a correction of the TL light attenuation plays a critical role for the proposed in situ calibration to be feasible and effective.

In the reading out of the thermoluminescence lights of the TLD-400 chips we accidentally found that TLD-400 chips irradiated in the BNCT beam were capable of emitting prominent scintillation lights owing to the induced 56Mn activity just like conventional inorganic scintillators do. Therefore, we explored the scintillation property of TLD-400 with an intention to develop the extra scintillation application of TLD-400 chips. The relative SC light sensitivity among some different types of TLD has been roughly estimated. The SC light counting rates readout by the TLD reader have been smartly applied to measure the activity of the induced 56Mn in the TLD-400 chip exposed to mixed neutron and gamma-ray fields. The attenuation of the SC lights in the TLD-400 chip has been studied based on a simplified attenuation model. The SC lights emitted by TLD-400 chips have also been applied for the activity measurements of small isotopic sources in direct contact with the TLD chips.

Chinese Abstract........................................................................................................i
Abstract.........................................................................................................................ii
Contents..................................................................................................................iv
Table List.....................................................................................................................viii
Figure Captions...............................................................................................................ix


Introduction.............................................................................................................. 1
1    Literature Survey…………………………………………………………………… 1
2    Motivation and Scope………………………………………………………………..3
  Materials and Methods…………………………………………………………………….4
1    TLD Measurement System…………………………………………………………..4
1.1    TLD…………………………………………………………………………4
1.2    TLD Reader…………………………………………………………………4
1.3    Planchet……………………………………………………………………..5
1.4    POM Ring………………………………………………………………….6
2    HPGe Counting System…………………………………………………….………6
3    BNCT Facility at THOR………………………………..............................................7
4    MCNPX Computer Code…………………………………………………………….9
  A Study on Annealing Technique for LiF:Mg,Cu,P Thermoluminescent Dosimeter…....11
1    Abstract…………………………………………………………….….………….11
2    Introduction…………………………………………………………….………….11
3    Material and Methods………………………………….……………….………….12
4    Results and Discussions…………………………………………………………..13
5    Conclusions……………………………………………….……………….………16
  Optimum Annealing and Readout Process……………………………..………………18
1    Annealing Process…………………………………………………………………18
2    Thermoluminescence Readout Process……………………….……………………18
2.1    CaF2 series TLD…………………………………………………………18
2.2    LiF series TLD…………………………………………………………….20
3    Scintillation Readout Process………………………………………………………20
  QA Measurement of Gamma-ray Dose and Neutron Activation Using TLD-400
for BNCT Beam……………………………………………………………………..…21
1    Abstract…………………………………………………..………….…………….21
2    Introduction……………………………………………………….……………….21
3    Materials and Methods………………………………..…………………………..24
3.1    Experimental Setup…………………………………..………………….24
3.2    Beam Characteristics in QA Phantom……………………..…………….25
3.3    Annealing and TL and SC Readout Processes for TLD-400…………….26
3.3.1    TLD Annealing………………………….………………………….27
3.3.2    TL Readout…………………………………………………………27
3.3.3    SC Readout……………………………….………………………….28
3.4    Determination of Mn Concentration in TLD-400 by Neutron Activation…………………………………..…………….………………..29
4    Results………………………………………………….…………………………30
4.1    Gamma-ray Dose Measurement…………………..……………………..30
4.2    Neutron Activation Measurement………………………………………..31
4.3    In Situ TL Calibration of TLD-400……………………………………….36
5    Conclusion………………………………………………………..……………….37
  The Attenuation of Thermoluminescence Light in TLD-400……….…………….……..38
1    Abstract………………………………………………………….……..………….38
2    Introduction…………………………………….………………….………………38
3    Materials and Methods…………………………………………………………….40
3.1    Experimental Setup ………………………………………….……….…40
3.1.1     TLD Equipment……………………..………………………………40
3.1.2     TLD Annealing………………..…………..………….……………..41
3.1.3     TL Readout………………………………………….………………41
3.2    Calibration Sources and Energy Deposition Distributions………..……….42
3.3    A Simplified Model for TL Light Attenuation in TLD…………….……43
4    Results and Discussions……………………………………………………………48
4.1    Attenuation Coefficient and Attenuation Correction Factor…….48
4.2    Apparent Calibration Factor and Intrinsic Calibration Factor……………..51
5    Conclusion……………………………………………………….………………..52
  An Exploration of the Scintillation Property of TLD-400………………………..……..55
1    Abstract……………………………………………………………..………………55
2    Introduction……………………………………………………………….……….55
3    Materials and Methods……………………………………………………………..56
3.1    Experimental Setup……………………………………………………….56
3.2    Measurement Sources and Energy Deposition Distribution…………..…..56
3.3    A Simplified Model for SC Light Attenuation in TLD………….……….57
4    Results and Discussion……………………………………………………………60
4.1    Comparison of SC Sensitivity among Different Types of TLD………..…60
4.2    Attenuation Coefficient and Attenuation Factor………….…..………….62
4.3    Apparent Calibration Factor and Intrinsic Calibration Factor……..…….64
5    Conclusion…………………………………………………………………………..65
  Conclusion and Future Work………………………..……………………………………66
1    Conclusion……………………………………..….……………………………….66
2    Future Work……………………………………..…………………………………..67

Reference………………………………………………..………………………………….68

                                

Aschan, C., Toivonen, M., Savolainen, S., and Stecher-Rasmussen, F., 1999. Experimental Correction for Thermal Neutron Sensitivity of Gamma Ray TL Dosemeters Irradiated at BNCT Beams. Radiat. Prot. Dosimetry, 82, 65–69.
Ayyangar, K., Reddy, A. R., Brownell, G. L., 1968. Some studies on thermoluminescence from LiF and other materials exposed to neutrons and other radiation. In: Proceedings of the 2nd International Conference on Luminescence Dosimetry. Springfield, VA: U.S. AEC Report CONF-680920, 525-542.
Bakshi, A.K., Chatterjee, S., Palani Selvam, T., Joshi, V.J., Chougaonkar, M.P., 2011. Determination of self attenuation coefficient and relative TL efficiency of CaSO4:Dy, LiF:Mg,Cu,P and LiF:Mg,Ti TLDs – An alternate approach. Nucl. Instr. Meth. B269, 2107–2110.
Bartlett, D.T., Edwards, A.A., 1979. The light conversion efficiency of TLD-700 for alpha particles relative to cobalt-60 gamma radiation. Phys. Med. Biol. 24, 1276–1283.
Bilski, P., Budzanowski, M., 2001. Self-Attenuation of TL light from LiF- a comparison of different experimental techniques. Radiat. Meas. 33, 679-685.
Bilski, P., Olko, P., Burgkhardt, B., Piesch, E., Waligorski, M.P.R., 1994. Thermoluminescence efficiency of LiF : Mg,Cu,P (MCP-N) detectors to photons, beta electrons, alpha-particles and thermal neutrons. Radiat. Prot. Dosim. 55, 31–38.
Delgado, A., 1996. Recent improvements in LiF: Mg, Ti and LiF: Mg, Cu, P based
enviromental dosimetry. Radiat. Prot. Dosimetry. 66 (1e4), 129e134.
Gambarini, G., Klamert, V., Agosteo, S., Birattari, C, Gay, S., Rosi, G., Scolari, L., 2004. Study of a Method Based on TLD Detectors for In-Phantom Dosimetry in BNCT. Radiat. Prot. Dosimetry 110, 631-636.
Gambarini, G., Magni, D., Regazzoni, V., Borroni, M., Carrara, M., Pignoli, E., Burian, J., Marek, M., Klupak, V., and Viererbl, L. 2014. Measurements of Gamma Dose and Thermal Neutron Fluence in Phantoms Exposed to a BNCT Epithermal Beam with TLD-700. Radiat. Prot. Dosimetry 161, 422-427.
Gambarinia, G., Gallivanonea, , F., Carrarac, M., Nagelsd, S., Vogtlandere, L., Hampele, G., Pirola, 2008. A study of reliability of TLDs for the photon dose mapping in reactor neutron fields for BNCT. Radiation Measurements 43, 1118-1122.
Horowitz, Y.S., Fraier, I., Kalefezra, J., 1979. “TL light self-absorption: implications for studies on the relative TL efficiency as a function of linear energy transfer”. Phys. Med. Biol. 24, 832–834.
Hosseini-Pooya, M., Jafarizadeh, M., 2004. “Effect of reader and oven annealing on the glow curve structure and fading of a LiF: Mg, Cu, P TL dosimeter”. J. Radiol. Prot. 24, 173e178.
Huang, C. K., Jiang, S. H., 2017. “Neutron activation analysis using a modified absolute calibration method”. J. Radioanal. Nucl. Chem 311, 1201-1207.
IAEA-TECDOC-1223 Technical reports series, 2001. “Current status of neutron capture therapy”. International Atomic Energy Agency.
JRT Associates Inc., http://jrtassociates.com/pdfs/tld_properties.pdf.
Knoll, G., 2000. Radiation Detection and Measurement, third ed. John Wiley & Sons, Inc..
Lin, Y. C., 2013. “Radiation Dose Rate Measurement in a Mixed Radiation Field Using Paired Ionization Chambers”. Doctoral dissertation, National Tsing Hua University, Hsinchu, Taiwan.
Liu, Y.-H., 2009. “The neutronic characterization of an epithermal neutron beam for boron neutron capture therapy”. Doctoral dissertation, National Tsing Hua University, Hsinchu, Taiwan.
Magill, J., 1999. An electronic chart of the nuclides on CD-ROM, European Commission. Institute of Transuranium Elements, Karlsruhe, Germany.
Majborn, B., Botter-Jensen, L., Christensen, P., 1977. “On the relative efficiency of TL phosphors for high-LET radiation”. In: Proceedings of the 5th International Conference On Luminescence Dosimetry. Physikalisches Institute, Giessen, pp. 124–130.
Martsolf, S. W., Johson, J. E., C. E. D., Vostmyer, Albertson, B. D., Binney, S. E., 1995. “Practical Considerations for TLD-400 /700-Based Gamma Ray Dosimetry for BNCT Applications in a High Thermal Neutron Fluence”. Health Phys.,69, 966-970.
Mckinlay, A. F., 1981. Thermoluminescence Dosimetry. Adam Hilger Ltd, Bristol, United Kingdom.
Mukherjee, B., Vana, N., 1984. “Self-absorption effect in LiF thermoluminescent dosimeters”. Nucl. Instr. Meth. 226, 572–573.
Olko, P., 2002. “The microdosimetric one-hit detector model for calculating the response of solid state detectors”. Radiat. Meas. 35, 255–267.
Olko, P., Bilski, P., Budzanowski, M., Waligorski, M.P.R., Fasso, A., Ipe, N., 1999. “Modelling of the thermoluminescence response of LiF:Mg,Cu,P (MCP-N) detectors after doses of low energy photons”. Radiat. Prot. Dosim. 84 (1–4), 103–107.
Pelowitz, D.B. (Ed.), 2008. MCNPXTM user’s manual version 2.6.0. Los Alamos National Laboratory, LA-CP-07-1473, April.
Raaijmakersa, C. P. J., Verhagen, H. W., Mijnheer, B. J., 1995. “Determination Of Dose Components in Phantoms Irradiated with an Epithermal Neutron Beam for Boron Neutron Capture Therapy”. Med. Phys. 22, 321-329.
Raaijmakersa, C. P. J., Watkins, P. R. D., Nottelman, E. L., Verhagen, H. W., Jansen, J. T. M., Zoetelief, J., Mijnheer, B. J., 1996. “The Neutron Sensitivity of Dosimeters Applied to Boron Neutron Capture Therapy”. Med. Phys., 23, 1581-1589.
RADAR Home Page, http://www.doseinfo-radar.com.
Saez-Vergara, J.C., Romero, A.M., 1996. “The influence of the heating system on the hypersensitive thermoluminescent material LiF: Mg, Cu, P (GR-200)”. Radiat. Prot. Dosimetry. 66 (1e4), 431e436.
Shinde, S.S., Dhabekar, B.S., Bhatt, B.C. 2001. Indigenously Developed LiF: Mg,Cu,P Thermoluminescent Phosphor for Radiation Dosimetric Application, In: Proceedings International Conference on Radiation Protection Measurements and Dosimetry: Current Practices and Future Trends, Mumbai, February 20e23, 2001.
THOR BNCT brochure, http://bnct.web.nthu.edu.tw/files/14-1155-12744,r11-1.php.
Tsai, W. C., and Jiang, S.H., 2011. “A study on annealing technique for LiF:Mg,Cu,P thermoluminescent dosimeter”. Radiat. Meas. 46, 1595-1597.
Voorbraak, W. P., 2003. Recommendations for the Dosimetry of Boron Neutron Capture Therapy (BNCT). NRG, Petten, The Netherlands.
Wang, J.N., Huang, C.K., Tsai, W.C., Liu, Y.H., Jiang, S.H., 2011. “Effective dose evaluation for BNCT treatment in the epithermal neutron beam at THOR”. Appl. Radiat. Isot. 69(12), 1850–1853.

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