磁质子反冲谱仪磁分析系统的模拟和实验研究
摘要
聚变反应产生的中子能谱携带等离子体中心区域的核心信息,如离子温度和燃料密度等,高性能的脉冲中子能谱诊断技术对聚变研究起着重要的作用。对于DT聚变中子(-14MeV),传统的飞行时间反冲质子谱仪需要较长的飞行距离,对实验空间和中子产额要求较高,且能量分辨率不够理想。磁质子反冲(Magnetic Proton Recoil, MPR)谱仪是近年来出现的一种新型的高性能诊断装置,可以近距离测量较低产额的DT聚变中子能谱,能够用于聚变离子温度和燃料密度的精确诊断。本论文致力于MPR技术的研究,设计了一种紧凑型MPR谱仪的磁分析系统,根据实际条件对系统进行了实验研究。
磁分析系统由均匀二极磁场和边缘场在水平面内实现“点-点”聚焦。运用带电粒子束光学理论和计算机软件对系统进行研究,计算了系统的束流传输参数,提出了具体的设计方案,在此基础上建立了带电粒子输运模拟程序,研究了系统的主要性能指标。根据模拟计算获得的带电粒子传输参数,设计了符合现阶段实验条件的实验系统。
C形钕铁硼永磁体磁极间隙为3cm,均匀场区场强约为0.792T。测量数据显示,均匀场区和边缘场区磁场分布达到了设计要求。使用实际磁场信息进行的粒子输运模拟计算表明：磁分析系统能实现4—8MeV反冲质子(45°反冲角)的动量分析,在整个能量范围内具有较为一致的分辨率；合适的质子限束光阑条件下,系统最大入射立体角约1.2ms(毫立体角),预计能量分辨率优于3%。
为检验磁分析系统的实际性能,使用239Pu放射α源进行了实验研究,测量了不同能量粒子的焦斑分布,研究了不同光阑尺寸和探测器位置等条件下焦斑的变化。实验结果表明,α粒子的运动轨迹(空间位置和偏转角)与理论计算和程序模拟结果一致,系统能量分辨率达到2%,能够很好地分辨5.15MeV和5.47MeV的α粒子。实验同时证明磁分析系统设计是合理的,建立的模拟计算程序为带电粒子分析提供了可靠的依据,为下一阶段的反冲质子实验研究提供了良好的实验基础。
结合磁分析系统的实际性能,对MPR谱仪的参数设置和相应的性能进行了分析和计算。MPR谱仪能够测量8—16MeV能量范围内的中子能谱,对于14MeV的准直入射中子具有4.5%的能量分辨率和0.85×10-8的探测效率。
Spectrum of neutrons produced in fusion reactions contains key parameters like ion temperature and fuel density in center part of plasma. High-performanced diagnostic technologies of pulsed neutron spectrum are important for fusion research. A widely used instrument in intense pulsed radiation field is the time-of-flight proton recoil spectrometer. However, flight distance of DT neutrons (～14MeV) is hardly available because of space limitation and neutron yield in some special experimental conditions.Magnetic proton recoil (MPR) spectrometer is a recently-appeared instrument to measure spectrum of low-yileded DT neutron at close distance, which can be used to accurately determine ion temperature and fuel density. The main aim of this thesis is to research the MPR technology. Magnetic analyzing system of a compact MPR spectrometer is designed and experimentally researched.
The magnetic analyzing system achieves "point-to-point" focus in the horizontal plane by homogeneous magnet field and fringing fields.The system is studied with the optics of charged particle beams and computer software. Parameters of beam transport are calculated and design of the system is proposed. Based on the design and calculations, an applicable beam transport simulation program is founded, and main performances of the system are researched. Considering the transport parameters obtained from theoretical calculation and simulation, experiment system for practical conditions is designed.
The C-shaped NdFeB permanent dipole with a pole gap of 3 cm produces a homogeneous field of 0.792 Tesla. Measurement shows that average intensity and fringing field of the dipole meet the requirements of the magnetic system. Simulations of charged particle beams with measured magnet field data show that protons with energy between 4MeV and 8MeV can be momentum analyzed with consistent resolution. Maximal incident solid angle of the system is about 1.2ms and the resolution is estimated to be better than 3% under appropriate settings of diaphragm dimension.
Experimental investigations are conducted with a 239Puαsource and CR-39 detectors to test performances of the system. Position distributions of a beams with different energies are measured under different settings of diaphragm dimension and detector position. The results show that tracks of a beams are accordant with theoretical calculations and simulations. Resolution of the system is about 2% andαparticles with energy of 5.15MeV and 5.47MeV can be distinguished.
Geometrical seetings and corresponding capabilities of the MPR spectrometer are studied according to performances of the magnetic analyzing system. Spectrum of neutrons with energy between 8MeV and 16MeV can be mearsured by the spectrometer. For collimated 14MeV neutrons, the detection efficiency is expected to be 0.85×10-8 with an energy resolution of about 4.5%.
磁分析系统由均匀二极磁场和边缘场在水平面内实现“点-点”聚焦。运用带电粒子束光学理论和计算机软件对系统进行研究,计算了系统的束流传输参数,提出了具体的设计方案,在此基础上建立了带电粒子输运模拟程序,研究了系统的主要性能指标。根据模拟计算获得的带电粒子传输参数,设计了符合现阶段实验条件的实验系统。
C形钕铁硼永磁体磁极间隙为3cm,均匀场区场强约为0.792T。测量数据显示,均匀场区和边缘场区磁场分布达到了设计要求。使用实际磁场信息进行的粒子输运模拟计算表明：磁分析系统能实现4—8MeV反冲质子(45°反冲角)的动量分析,在整个能量范围内具有较为一致的分辨率；合适的质子限束光阑条件下,系统最大入射立体角约1.2ms(毫立体角),预计能量分辨率优于3%。
为检验磁分析系统的实际性能,使用239Pu放射α源进行了实验研究,测量了不同能量粒子的焦斑分布,研究了不同光阑尺寸和探测器位置等条件下焦斑的变化。实验结果表明,α粒子的运动轨迹(空间位置和偏转角)与理论计算和程序模拟结果一致,系统能量分辨率达到2%,能够很好地分辨5.15MeV和5.47MeV的α粒子。实验同时证明磁分析系统设计是合理的,建立的模拟计算程序为带电粒子分析提供了可靠的依据,为下一阶段的反冲质子实验研究提供了良好的实验基础。
结合磁分析系统的实际性能,对MPR谱仪的参数设置和相应的性能进行了分析和计算。MPR谱仪能够测量8—16MeV能量范围内的中子能谱,对于14MeV的准直入射中子具有4.5%的能量分辨率和0.85×10-8的探测效率。
Spectrum of neutrons produced in fusion reactions contains key parameters like ion temperature and fuel density in center part of plasma. High-performanced diagnostic technologies of pulsed neutron spectrum are important for fusion research. A widely used instrument in intense pulsed radiation field is the time-of-flight proton recoil spectrometer. However, flight distance of DT neutrons (～14MeV) is hardly available because of space limitation and neutron yield in some special experimental conditions.Magnetic proton recoil (MPR) spectrometer is a recently-appeared instrument to measure spectrum of low-yileded DT neutron at close distance, which can be used to accurately determine ion temperature and fuel density. The main aim of this thesis is to research the MPR technology. Magnetic analyzing system of a compact MPR spectrometer is designed and experimentally researched.
The magnetic analyzing system achieves "point-to-point" focus in the horizontal plane by homogeneous magnet field and fringing fields.The system is studied with the optics of charged particle beams and computer software. Parameters of beam transport are calculated and design of the system is proposed. Based on the design and calculations, an applicable beam transport simulation program is founded, and main performances of the system are researched. Considering the transport parameters obtained from theoretical calculation and simulation, experiment system for practical conditions is designed.
The C-shaped NdFeB permanent dipole with a pole gap of 3 cm produces a homogeneous field of 0.792 Tesla. Measurement shows that average intensity and fringing field of the dipole meet the requirements of the magnetic system. Simulations of charged particle beams with measured magnet field data show that protons with energy between 4MeV and 8MeV can be momentum analyzed with consistent resolution. Maximal incident solid angle of the system is about 1.2ms and the resolution is estimated to be better than 3% under appropriate settings of diaphragm dimension.
Experimental investigations are conducted with a 239Puαsource and CR-39 detectors to test performances of the system. Position distributions of a beams with different energies are measured under different settings of diaphragm dimension and detector position. The results show that tracks of a beams are accordant with theoretical calculations and simulations. Resolution of the system is about 2% andαparticles with energy of 5.15MeV and 5.47MeV can be distinguished.
Geometrical seetings and corresponding capabilities of the MPR spectrometer are studied according to performances of the magnetic analyzing system. Spectrum of neutrons with energy between 8MeV and 16MeV can be mearsured by the spectrometer. For collimated 14MeV neutrons, the detection efficiency is expected to be 0.85×10-8 with an energy resolution of about 4.5%.
引文
1Б.Ю.萨尔柯夫.惯性约束核聚变现状与能源前景[M].北京：原子能出版社,2008:4
2朱士尧.核聚变原理[M].合肥：中国科学技术大学出版社,1992:10
3邱励俭.核聚变研究50年[J].核科学与工程,2001;21(1):29～38
4 H.Azechi, H.Shiraga, N. Miyanaga, et al. Review of ICF plasma diagnostics [J].Fusion Engineering and Design,1997;34-35:37～44
5 A.V. Krasilnikov, M. Sasao, Yu.A. Kaschuck, et al. Status of ITER neutron diagnostic development[J]. Nuclear Fusion,2005;12(45):1503
6 T.Iguchi,J.Kaneko, M. Nakazawa, et al. Conceptual design of neutron diagnostic systems for fusion experimental reactor [J].Fusion Engineering and Design,1995;28:689～698
7 J.Mlynar, G. Bonheure, A. Murari, et al.Progress in neutron diagnostics at JET [J].Czechoslovak Journal of Physics,2006;56(B):118～124
8 V. Yu. Glebov, C. A. Barrera, S.E. Caldwell, et al. Development of nuclear diagnostics for the National Ignition Facility (invited) [J].Review of scientific instruments,2006; 77:10E715
9 O.N.Jarvis. Neutron spectrometry at JET(1983-1999) [J].Nuclear Instruments and Methods in Physics Research,2002;476(A):474-484
10汲长松.中子探测实验方法[M].北京：原子能出版社,1998:209
11 G. J.Schmid, R. L. Griffith, V.Yu. Glebov, et al. CVD diamond as a high bandwidth neutron detector for inertial confinement fusion diagnostics [J].Review of scientific instruments,2003;74(3):1828～1831
12 M.Pillon, M. Angelone, D. Lattanzi, et al. Neutron detection at jet using artificial diamond detectors [J]. Fusion Engineering and Design,2007;82:1174～1178
13杨进蔚,郦文忠,张炜.托卡马克中聚变中子的能谱测量[J].科学技术与工程,2003;3(4):360-363
14 F. Foulona, P. Bergonzoa, V.N.Amosovb, et al. Characterisation of CVD diamond detectors used for fast neutron flux monitoring[J].Nuclear Instruments and Methods in Physics Research.2002; A476:495
15 R. G. Watt, R.E. Chrien, K. A. Klare, et al. A sensitive neutron spectrometer for the National Ignition Facility[J].Review of Scientific Instruments,2001;72:846～849
16刘庆照.脉冲辐射场诊断技术[M].北京：科学出版社,1994:531
17 J.Kallne, L. Ballabio, S. Conroy, et al.New neutron diagnostics with the magnetic proton recoil spectrometer [J].Review of Scientific Instruments,1999; 70(1):1181～1184
18 L. Giacomelli, A. Hjalmarsson, H. Sjostrand, et al. Advanced neutron diagnostics for JET and ITER fusion experiments [J].Nuclear Fusion,2005;45:1191～1201.
19 H. Sjostrand, L. Giacomelli, E. Andersson Sunden, et al.The new MPRu instrument for neutron emission spectroscopy at JET[J].Review of Scientific Instruments,2006; 77:10E717
20 J.A. Frenje, T. C. Sangster, V. Yu. Glebov, et al. A neutron spectrometer for precise measurements of DT neutrons from 10 to 18 MeV at OMEGA and the National Ignition Facility[J].Review of Scientific Instruments,2001;72(1):854～858
21吕建钦.带电粒子束光学.北京：高等教育出版社,2004:126-149
22 PSI Graphic Transport Framework by U.Rohrer based on a CERN-SLAC-FERMILAB version by K. L. Browm, et al.
23朱润生.固体核径迹探测器的原理和应用[M].北京：科学出版社,1987;229-232
24王兴功,骆亿生,张红,等.CR-39固体核径迹探测器用于中子测量化学蚀刻参数的优化[J].核技术,2005;28(2):319～323
25尚兵,汪家兴.国产CR-39塑料膜测量α粒子的研究[J].核技术,1988;11(7):47
26南亲良,罗平安,王尔为.CR39固态核径迹探测器快中子灵敏度曲线的理论解释[J].原子能科学技术,2009；34:190
27许伟,李天柁,马文彦等.固体核径迹探测器最佳蚀刻条件选择[A].见：第十二届全国核电子学与核探测技术学术年会论文集[C],第十二届全国核电子学与核探测技术学术年,四川江油,2004:119～121
28田东风,孙伟力.中子核反应激发函数[M].北京：国防工业出版社,2006:98
29 National Institute of Science and Technology. Stopping Power Table for Protons[EB/OL].2005, http://physics.nist.gov/PhysRefData/Star/Text/PSTAR.html
30范佳锦,李君利等.能量沉积计数的强迫碰撞随机游动方法[J].中国科学,2003;33(E):452～458
31 G. Ericsson, L. Ballabio, S.Conroy, et al. Neutron emission spectroscopy at JET-Results from the magnetic proton recoil spectrometer[J].Review of Scientific Instruments,2001;72(1):759
32 J. Frenje, L. Ballabio, S.Conroy, et al.Neutron emission Doppler-shift measurements in deuterium-tritium plasmas [J].Review of Scientific Instruments,1999; 70(1):1176～1180
33 Hans Henriksson, L. Ballabio, S.Conroy, et al. Neutron emission study of DT plasmas heated with tritium neutral beams [J].Review of Scientific Instruments,2001;72(1):832～835
34 N. P. Hawkes, P. van Belle, D. S. Bond, et al.A 14 MeV neutron spectrometer for the Joint European Torus deuterium-tritium experiments [J].Review of Scientific Instruments,1999;70(1):1134～1136
35 M.Tardocchi, et al. Ion temperature and plasma rotation profile effects in the neutron emission spectrum [J].Review of Scientific Instruments,2004,75(3):661～668
36 M.Tardocchi, G. Gorini, E. Andersson Sund6n, et al. Modeling of neutron emission spectroscopy in JET discharges with fast tritons from (T)D ion cyclotron heating [J].Review of Scientific Instruments,2006; 77:126107.
37 L. Ballabio, J.Frenje, J.Kallne, et al.Measurement and interpretation of the spectrum of the triton burnup neutron emission from deuterium tokamak plasmas [J].Nuclear Fusion,2000,40:21～33.
38 M. Tardocchi, S. Conroy, G..Ericsson, et al. The monitoring system of a high performance fusion neutron spectrometer [J].Nuclear Instruments and Methods in Physics Research,2002;A485:624～639
39 J.A. Frenje, C. K. Li, F. H.Seguin, et al. Measurements of fuel and shell areal densities of OMEGA capsule implosions using elastically scattered protons [J].Physics of plasmas.2002; 9:4719～4726.
40 J.Kallne, and G.Gorini. Count rate performance of spectrometers for fusion neutrons [J].Review of Scientific Instruments,1993;64:2765～2770.
41 S.Croft,D. S.Bonf,N. P. Hawkes,et al. An efficient 14-MeV neutron detector for use in mixed 2.5 and 14 MeV neutron beams[J].Review of Scientific Instruments,1993;64:1418～1423.
42 W. A. Noonan, F. C.Young, E. P. Donovan, et al.. A magnetic spectrometer for intense pulsed proton beams [J].Review of Scientific Instruments,1995,66:342-344.
43 M. Tardocchi, G,Gorini, D. Palma, et al.Control and monitoring system for fusion neutron spectroscopy on the Joint European Torus. [J] Review of Scientific Instruments,2004; 75:3543～3546
44 A. Zimbal, L. Bertalot, J.M.Adams, et al.Compact NE213 neutron spectrometer with high energy resolution for fusion applications [J].Review of Scientific Instruments,2004;75(10):3553～3555
45 L. Giacomelli, G. Gorini, A. Murari, et al. Development and characterization of the proton recoil detector for the MPRu neutron spectrometer [J].Review of Scientific Instruments,2006; 77:10E708.
2朱士尧.核聚变原理[M].合肥：中国科学技术大学出版社,1992:10
3邱励俭.核聚变研究50年[J].核科学与工程,2001;21(1):29～38
4 H.Azechi, H.Shiraga, N. Miyanaga, et al. Review of ICF plasma diagnostics [J].Fusion Engineering and Design,1997;34-35:37～44
5 A.V. Krasilnikov, M. Sasao, Yu.A. Kaschuck, et al. Status of ITER neutron diagnostic development[J]. Nuclear Fusion,2005;12(45):1503
6 T.Iguchi,J.Kaneko, M. Nakazawa, et al. Conceptual design of neutron diagnostic systems for fusion experimental reactor [J].Fusion Engineering and Design,1995;28:689～698
7 J.Mlynar, G. Bonheure, A. Murari, et al.Progress in neutron diagnostics at JET [J].Czechoslovak Journal of Physics,2006;56(B):118～124
8 V. Yu. Glebov, C. A. Barrera, S.E. Caldwell, et al. Development of nuclear diagnostics for the National Ignition Facility (invited) [J].Review of scientific instruments,2006; 77:10E715
9 O.N.Jarvis. Neutron spectrometry at JET(1983-1999) [J].Nuclear Instruments and Methods in Physics Research,2002;476(A):474-484
10汲长松.中子探测实验方法[M].北京：原子能出版社,1998:209
11 G. J.Schmid, R. L. Griffith, V.Yu. Glebov, et al. CVD diamond as a high bandwidth neutron detector for inertial confinement fusion diagnostics [J].Review of scientific instruments,2003;74(3):1828～1831
12 M.Pillon, M. Angelone, D. Lattanzi, et al. Neutron detection at jet using artificial diamond detectors [J]. Fusion Engineering and Design,2007;82:1174～1178
13杨进蔚,郦文忠,张炜.托卡马克中聚变中子的能谱测量[J].科学技术与工程,2003;3(4):360-363
14 F. Foulona, P. Bergonzoa, V.N.Amosovb, et al. Characterisation of CVD diamond detectors used for fast neutron flux monitoring[J].Nuclear Instruments and Methods in Physics Research.2002; A476:495
15 R. G. Watt, R.E. Chrien, K. A. Klare, et al. A sensitive neutron spectrometer for the National Ignition Facility[J].Review of Scientific Instruments,2001;72:846～849
16刘庆照.脉冲辐射场诊断技术[M].北京：科学出版社,1994:531
17 J.Kallne, L. Ballabio, S. Conroy, et al.New neutron diagnostics with the magnetic proton recoil spectrometer [J].Review of Scientific Instruments,1999; 70(1):1181～1184
18 L. Giacomelli, A. Hjalmarsson, H. Sjostrand, et al. Advanced neutron diagnostics for JET and ITER fusion experiments [J].Nuclear Fusion,2005;45:1191～1201.
19 H. Sjostrand, L. Giacomelli, E. Andersson Sunden, et al.The new MPRu instrument for neutron emission spectroscopy at JET[J].Review of Scientific Instruments,2006; 77:10E717
20 J.A. Frenje, T. C. Sangster, V. Yu. Glebov, et al. A neutron spectrometer for precise measurements of DT neutrons from 10 to 18 MeV at OMEGA and the National Ignition Facility[J].Review of Scientific Instruments,2001;72(1):854～858
21吕建钦.带电粒子束光学.北京：高等教育出版社,2004:126-149
22 PSI Graphic Transport Framework by U.Rohrer based on a CERN-SLAC-FERMILAB version by K. L. Browm, et al.
23朱润生.固体核径迹探测器的原理和应用[M].北京：科学出版社,1987;229-232
24王兴功,骆亿生,张红,等.CR-39固体核径迹探测器用于中子测量化学蚀刻参数的优化[J].核技术,2005;28(2):319～323
25尚兵,汪家兴.国产CR-39塑料膜测量α粒子的研究[J].核技术,1988;11(7):47
26南亲良,罗平安,王尔为.CR39固态核径迹探测器快中子灵敏度曲线的理论解释[J].原子能科学技术,2009；34:190
27许伟,李天柁,马文彦等.固体核径迹探测器最佳蚀刻条件选择[A].见：第十二届全国核电子学与核探测技术学术年会论文集[C],第十二届全国核电子学与核探测技术学术年,四川江油,2004:119～121
28田东风,孙伟力.中子核反应激发函数[M].北京：国防工业出版社,2006:98
29 National Institute of Science and Technology. Stopping Power Table for Protons[EB/OL].2005, http://physics.nist.gov/PhysRefData/Star/Text/PSTAR.html
30范佳锦,李君利等.能量沉积计数的强迫碰撞随机游动方法[J].中国科学,2003;33(E):452～458
31 G. Ericsson, L. Ballabio, S.Conroy, et al. Neutron emission spectroscopy at JET-Results from the magnetic proton recoil spectrometer[J].Review of Scientific Instruments,2001;72(1):759
32 J. Frenje, L. Ballabio, S.Conroy, et al.Neutron emission Doppler-shift measurements in deuterium-tritium plasmas [J].Review of Scientific Instruments,1999; 70(1):1176～1180
33 Hans Henriksson, L. Ballabio, S.Conroy, et al. Neutron emission study of DT plasmas heated with tritium neutral beams [J].Review of Scientific Instruments,2001;72(1):832～835
34 N. P. Hawkes, P. van Belle, D. S. Bond, et al.A 14 MeV neutron spectrometer for the Joint European Torus deuterium-tritium experiments [J].Review of Scientific Instruments,1999;70(1):1134～1136
35 M.Tardocchi, et al. Ion temperature and plasma rotation profile effects in the neutron emission spectrum [J].Review of Scientific Instruments,2004,75(3):661～668
36 M.Tardocchi, G. Gorini, E. Andersson Sund6n, et al. Modeling of neutron emission spectroscopy in JET discharges with fast tritons from (T)D ion cyclotron heating [J].Review of Scientific Instruments,2006; 77:126107.
37 L. Ballabio, J.Frenje, J.Kallne, et al.Measurement and interpretation of the spectrum of the triton burnup neutron emission from deuterium tokamak plasmas [J].Nuclear Fusion,2000,40:21～33.
38 M. Tardocchi, S. Conroy, G..Ericsson, et al. The monitoring system of a high performance fusion neutron spectrometer [J].Nuclear Instruments and Methods in Physics Research,2002;A485:624～639
39 J.A. Frenje, C. K. Li, F. H.Seguin, et al. Measurements of fuel and shell areal densities of OMEGA capsule implosions using elastically scattered protons [J].Physics of plasmas.2002; 9:4719～4726.
40 J.Kallne, and G.Gorini. Count rate performance of spectrometers for fusion neutrons [J].Review of Scientific Instruments,1993;64:2765～2770.
41 S.Croft,D. S.Bonf,N. P. Hawkes,et al. An efficient 14-MeV neutron detector for use in mixed 2.5 and 14 MeV neutron beams[J].Review of Scientific Instruments,1993;64:1418～1423.
42 W. A. Noonan, F. C.Young, E. P. Donovan, et al.. A magnetic spectrometer for intense pulsed proton beams [J].Review of Scientific Instruments,1995,66:342-344.
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