分子离子研究装置低能传输线设计
摘要
重离子加速器冷却储存环是分子离子复合离解研究的有力工具,当前国际上一些实验室已经开展了相关研究工作,由于磁刚度的限制,这些实验室只能对质量数低于70amu的分子离子进行研究。中国科学院近代物理研究所重离子加速器冷却储存环CSRe具有较高的磁刚度,适合对高质荷比的重离子开展研究工作。中国科学院近代物理研究所拟在CSRe上建设分子离子复合离解研究装置(Molecular Ion Dissociative Recombination Research Facility-MIRF),以开展高质量数分子离子的研究工作,本论文的主要工作是设计MIRF低能束流传输系统(LEBT)。
基于CSRe原有的Lattice结构,需要设计一条独立的分子离子注入线,以完成分子离子的加速、传输及CSRe的注入。MIRF注入线按能量划分为低能传输系统(LEBT)和中能传输系统(MEBT)。MIRF-LEBT主要由150kV倍压型高压加速器、聚焦元件和磁分析系统组成,辅助设备包括束诊元件、真空系统、水冷系统及控制系统。
MIRF-LEBT拟采用先加速后分析的设计方案,其中,低能加速系统主要由一台150kV倍压型高压加速器组成。采用了Poisson/Superfish软件对所设计的150kV倍压型高压加速器电场分布进行了模拟,模拟显示加速器各区域空间电场值都远低于击穿电场限值。不用Beampath程序对高压加速器中的束流传输进行了模拟,束流包络显示,加速区电场对分子离子束具有较强的聚焦作用,加速管出口的束斑尺寸较小,束流品质较高。
设计方案中拟采用组合四极透镜(Triplet)对加速后的分子离子束进行聚焦,并采用二极磁铁对分子离子进行分析。采用Trace-3D程序对束流的传输状态进行了模拟,模拟结果显示：质量数50～150amu范围的分子离束都能实现较好的匹配专输。为进一步验证磁分析系统的分辨能力,采用Beampath程序分别对不同质量数的束流传输进行了模拟,模拟显示：通过调节分析磁铁前Triplet的磁感应强度,不同质量数的分子离子都能够在分析狭缝光阑附近形成束腰,质荷比接近的离子束斑明显分离。说明分析系统的质量分辨达到设目标。
由于不同质量数的束流经过分析系统后的Twiss参数差距较大,设计了第二组三组合四极透镜对束流实现聚焦和发射相图变换,通过模拟显示：不同质量数的束流发射相图都能落在RFQ接受相图内。论文最后给出了MIRF-LEBT各元件的设计方案和详细参数,完成了CSRe分子离子研究装置低能传输系统的物理设计。
Heavy ion accelerator storage ring is a powerful tool for researching the molecular ion dissociative recombination, some laboratories have carried out the related research work. Due to the limitations of the magnetic rigidity, they merely carried on the study of the molecular ion that mass is less than70amu. The storage ring CSRe at the Institute of Modern Physics, can provide enough magnetic rigidity to carry out research on heavy ion of high mass charge ratio. A Molecular Ion Dissociative Recombination Research Facility (MIRF) program for higher-mass molecular ion research is proposing in Institute of Modern Physics, Chinese Academy of Sciences. The main work of this thesis is the design of The low energy beam transport system (LEBT) for MIRF.
Based on the original structure of CSRe Lattice, the project require to design a separate molecular ion injection line to accelerate, transmit and inject into CSRe. The MIRF injection line is composed of the Low Energy Transport System (LEBT) and Middle Energy Transport System (MEBT) according to different energy. The MIRF-LEBT is mainly composed of150kV high-voltage accelerators, focusing elements and magnetic analysis system. Its auxiliary equipments include beam diagnosis components, vacuum system, cooling system and control system.
The electric field distribution of the150kV voltage high-voltage accelerator is calculated by the Poisson/Superfish code.The simulation results indicates that the values of electric field of acceleration space were far lower than the value of breakdown electric field. The beam transmission process is simulated using Beampath code. The beam envelope reveals that the acceleration field has a strong focusing effect for the molecular ion beam which means beam spot size at accelerating tube exit is small.
The simulation from Trace-3D shows that with the focus of the triplet, the molecular ion whose mass range between50～150amu can match to the entrance of the analysis magnets. In order to check the resolving power of the analysis system, we simulated the beam transport of different mass by the Beampath code. The simulation result shows that with the adjustable triplet in front of the analysis magnet, molecular ions of different mass-to-charge ratio will separate apparently.
A second triplet is design to focus on beam and to transform phase space, because the Twiss parameters difference that the distinctive mass-to-charge ratio beam through the analysis system. The simulation shows that all kinds of beam can located within the acceptance of the RFQ. Finally, the thesis gives the detailed parameters of each component of MIRF-LEBT. which means the physical design of the low energy transmission system for CSRe Molecular Ion Research Facility has finished.
基于CSRe原有的Lattice结构,需要设计一条独立的分子离子注入线,以完成分子离子的加速、传输及CSRe的注入。MIRF注入线按能量划分为低能传输系统(LEBT)和中能传输系统(MEBT)。MIRF-LEBT主要由150kV倍压型高压加速器、聚焦元件和磁分析系统组成,辅助设备包括束诊元件、真空系统、水冷系统及控制系统。
MIRF-LEBT拟采用先加速后分析的设计方案,其中,低能加速系统主要由一台150kV倍压型高压加速器组成。采用了Poisson/Superfish软件对所设计的150kV倍压型高压加速器电场分布进行了模拟,模拟显示加速器各区域空间电场值都远低于击穿电场限值。不用Beampath程序对高压加速器中的束流传输进行了模拟,束流包络显示,加速区电场对分子离子束具有较强的聚焦作用,加速管出口的束斑尺寸较小,束流品质较高。
设计方案中拟采用组合四极透镜(Triplet)对加速后的分子离子束进行聚焦,并采用二极磁铁对分子离子进行分析。采用Trace-3D程序对束流的传输状态进行了模拟,模拟结果显示：质量数50～150amu范围的分子离束都能实现较好的匹配专输。为进一步验证磁分析系统的分辨能力,采用Beampath程序分别对不同质量数的束流传输进行了模拟,模拟显示：通过调节分析磁铁前Triplet的磁感应强度,不同质量数的分子离子都能够在分析狭缝光阑附近形成束腰,质荷比接近的离子束斑明显分离。说明分析系统的质量分辨达到设目标。
由于不同质量数的束流经过分析系统后的Twiss参数差距较大,设计了第二组三组合四极透镜对束流实现聚焦和发射相图变换,通过模拟显示：不同质量数的束流发射相图都能落在RFQ接受相图内。论文最后给出了MIRF-LEBT各元件的设计方案和详细参数,完成了CSRe分子离子研究装置低能传输系统的物理设计。
Heavy ion accelerator storage ring is a powerful tool for researching the molecular ion dissociative recombination, some laboratories have carried out the related research work. Due to the limitations of the magnetic rigidity, they merely carried on the study of the molecular ion that mass is less than70amu. The storage ring CSRe at the Institute of Modern Physics, can provide enough magnetic rigidity to carry out research on heavy ion of high mass charge ratio. A Molecular Ion Dissociative Recombination Research Facility (MIRF) program for higher-mass molecular ion research is proposing in Institute of Modern Physics, Chinese Academy of Sciences. The main work of this thesis is the design of The low energy beam transport system (LEBT) for MIRF.
Based on the original structure of CSRe Lattice, the project require to design a separate molecular ion injection line to accelerate, transmit and inject into CSRe. The MIRF injection line is composed of the Low Energy Transport System (LEBT) and Middle Energy Transport System (MEBT) according to different energy. The MIRF-LEBT is mainly composed of150kV high-voltage accelerators, focusing elements and magnetic analysis system. Its auxiliary equipments include beam diagnosis components, vacuum system, cooling system and control system.
The electric field distribution of the150kV voltage high-voltage accelerator is calculated by the Poisson/Superfish code.The simulation results indicates that the values of electric field of acceleration space were far lower than the value of breakdown electric field. The beam transmission process is simulated using Beampath code. The beam envelope reveals that the acceleration field has a strong focusing effect for the molecular ion beam which means beam spot size at accelerating tube exit is small.
The simulation from Trace-3D shows that with the focus of the triplet, the molecular ion whose mass range between50～150amu can match to the entrance of the analysis magnets. In order to check the resolving power of the analysis system, we simulated the beam transport of different mass by the Beampath code. The simulation result shows that with the adjustable triplet in front of the analysis magnet, molecular ions of different mass-to-charge ratio will separate apparently.
A second triplet is design to focus on beam and to transform phase space, because the Twiss parameters difference that the distinctive mass-to-charge ratio beam through the analysis system. The simulation shows that all kinds of beam can located within the acceptance of the RFQ. Finally, the thesis gives the detailed parameters of each component of MIRF-LEBT. which means the physical design of the low energy transmission system for CSRe Molecular Ion Research Facility has finished.
引文
[1]Thomson, J. J. Bakerian Lecture:Rays of Positive Electricity. Proceedings of the Royal Society A:Mathematical, Physical and Engineering Sciences.1913,89 (607):1.
[2]Herzberg G. Some historical remarks.The physics and chemistry of interstellar molecular clouds(Lecture notes in physics 331), Berlin:Springer,1989,1～2
[3]Physical Processes in the Interstellar Medium, L. Spitzer,1978 (New York:Wiley)
[4]李守中.一个了解宇宙的新窗口.现代物理知识,1991, (4):22～23;(5):17-19; (6):9～10; 1992,(1):31～32; (2):14～15
[5]Adams N G, Poterya V,Babcock L M.Mass Spectrom Rev,2006,25:798.
[6]李守中.分子天体物理学的进展及其对认识论的一些启示.北京大学学报(哲学社会科学版),1990,(3)：85～92
[7]Geppert W D,Thomas R,Semaniak J,et al.Astrophys J,2004,609:459.
[8]Thomas R D.Mass Spectrom Rev,2008,27:485.
[9]孙锦,李守中.分子天文学.北京：高等教育出版社,1996
[10]H.T.Edwards, Proc. of 14th International Conference on High Energy Accelerators, P.151, (1989)
[11]王书鸿,高能物理与核物理,Vol.10,No.6,697,1986.
[12]Townes CH. The early years of research on astronomical masers. Astrophysics Masers,1989, 3～11
[13]Geppert W D,Larsson M.Molecular Physics,2008,106:2199.
[14]Larsson M,Orel A E.Dissociative Recombination of Molecular Ions.New York.Cambridge University Press,2008,315—320.
[15]E. Jaeschke, D. Kramer, W. Arnold, G. Bisoffi, M. Blurn:A. Friedrich, C. Geyer, M. Grieser, B. Habs, H. LV. Heyng, B. Holzer, R. Ihde, M. Jung, K. Matl, R. Neumann,.4. Noda, W. Ott, B. Povh, R. Repnow, F. Schmitt, M. Steck, E. Steffens,1988 European Particle Accelera-tor Conference. Rome, vol.1, p.365.
[16]M Grieser, D.Habs, R.v.Hahn, C.M.Kleffner, R.Repnow, M.Stampfer,E.Jaeschke and M.Steck,1991 IEEE Particle Accelerator Conference, San Francisco,vol.5,p.2817
[17]H. Danared,Electron cooling at CRYRING,Phys. Scr.48,405 (1993).
[18]S.Datz and M. Larsson,Radiative lifetimes for all vibrational levels in the X 1∑+ state of HeH+ and its relevance to dissociative recombination experiments in ion storage rings,Phys. Scr.46 (1992)343.
[19]Hangst, J.S.; et al. (1992). "Laser cooling of stored ions in ASTRID:A storage ring for ions and electrons". Nuclear Instruments and Methods in Physics Research Section B 68: 17.Bibcode:1992NIMPB..68...17H.doi:10.1016/0168-583X(92)96042-W.
[20]"Beamlines on ASTRID". Institute for Storage Ring Facilities.13 June 2009. Retrieved 2012-04-01.
[21]Florescu-Mitchell A I,Mitchell J B A.Phys Rep,2006,430:277.
[22]蔡晓红,于得洋,杨建成,等.原子核物理评论,2010,27(3)：164CAI Xiao-hong, YU Deyang,YANG Jiancheng,Nuclear Physics Review,2010,27(3):164(in Chinese)
[15]Xia J W, Rao Y N, Yuan YJ, et al. HIRFL-CSR PLAN, The 6th China-Japan Joint Symposium on Accelerators for Nuclear Science and Their Applications,1996.10, Chengdu, China, P24—27
[16]Xia J W, Zhan W L, Wei B W, et al. The Heavy Ion Cooler-storage-Ring Project (HIRFL-CSR) at Lanzhou. NMA,2002,488:11—25
[25]詹文龙,魏宝文,等.兰州重离子冷却储存环[J].原子核物理评论,2001,18(1)：35236.(Xia J W, Zhan W L, Wei BW, et al. HIRFL-CSR heavy ion research facility. Nuclear Physics Review,2001,18(1):35236)
[26]陈佳洱主编,加速器物理基础,原于能出版社,1993
[27]王书鸿,罗紫华和罗应雄著,质子直线加速器原理,原子能出版社,1986
[28]桂伟燮,荷电粒子加速器原理,清华大学出版社(第一版),1994：169。
[29]孙别和,夏佳文.强流离子束的束包络方程与束包络计算.兰州大学学报(自然科学版),1990,26(4)：55
[30]"Handbook of ion sources" Bernhard Wolf (Ed.) (1995).
[31]SUN Liang-Ting,LI Jin-Yu,et ai Commission Test of LAPECR2 Source on the 320kV HV Platform.HICH ENERGY PHYSICS AND NUCLEAR PHYSICS.2007,31(1) 55-59
[32]姚泽恩,苏桐龄,姜汴婴.核技术,1992,15(12)：731-734YAO Zeen, SU Tongling, JIANG Bianying. Nucl Tech,1992,15(12):731-734
[33]苏桐龄,强流中子发生器及其应用,核技术,12(8,9)1989：553-556.
[34]姚泽恩,强磁透镜的物理设计报告,1997年(内部资料)
[35]姚泽恩,刘国汉,贾文宝,苏桐龄,董明义,磁镜场空间电荷透镜初步研究,甘肃科学：,Vol.13,No.3,2001：59-63.
[36]Zeen Yao, Tongling Su, Shang wen Cheng, et al. Design status of an intense 14MeV neutron source for cancer therapy[J]. Nuclear Instruments and Methods in Physics Research A,2002,490 (3):566-572.
[37]姚泽恩,苏桐龄,陈尚文等.用于治疗癌症的强流中子发生器束流光路设计[J].兰州大学学报(n然利·学版),2000,36(1)：28-33.Yao Zeen, Su Tongling, Chen Shangwen, et al. Beam Optics of Intense Neutron Generator for Cancer Therapy [J]. Journal of Lanzhou University (Natural Science),2000,36 (1):28-33.
[38]PIAO Yubo,LI Gongping,QIAN Defeng,et al.A space charge lens consisting of negative electrode and magnetic mirror [J].Atomic Energy Science and Technology,1990,42(2):1-6(in Chinese).(朴禹伯,李公平,钱德丰,等.一种由负电极和磁透镜组成的空间电荷透镜[J].原子能科学技术,1990,42(2)：1-6.)
[39]郁庆长,强流带电粒子束的传输矩阵理论,核技术,10(4)1987：38
[2]Herzberg G. Some historical remarks.The physics and chemistry of interstellar molecular clouds(Lecture notes in physics 331), Berlin:Springer,1989,1～2
[3]Physical Processes in the Interstellar Medium, L. Spitzer,1978 (New York:Wiley)
[4]李守中.一个了解宇宙的新窗口.现代物理知识,1991, (4):22～23;(5):17-19; (6):9～10; 1992,(1):31～32; (2):14～15
[5]Adams N G, Poterya V,Babcock L M.Mass Spectrom Rev,2006,25:798.
[6]李守中.分子天体物理学的进展及其对认识论的一些启示.北京大学学报(哲学社会科学版),1990,(3)：85～92
[7]Geppert W D,Thomas R,Semaniak J,et al.Astrophys J,2004,609:459.
[8]Thomas R D.Mass Spectrom Rev,2008,27:485.
[9]孙锦,李守中.分子天文学.北京：高等教育出版社,1996
[10]H.T.Edwards, Proc. of 14th International Conference on High Energy Accelerators, P.151, (1989)
[11]王书鸿,高能物理与核物理,Vol.10,No.6,697,1986.
[12]Townes CH. The early years of research on astronomical masers. Astrophysics Masers,1989, 3～11
[13]Geppert W D,Larsson M.Molecular Physics,2008,106:2199.
[14]Larsson M,Orel A E.Dissociative Recombination of Molecular Ions.New York.Cambridge University Press,2008,315—320.
[15]E. Jaeschke, D. Kramer, W. Arnold, G. Bisoffi, M. Blurn:A. Friedrich, C. Geyer, M. Grieser, B. Habs, H. LV. Heyng, B. Holzer, R. Ihde, M. Jung, K. Matl, R. Neumann,.4. Noda, W. Ott, B. Povh, R. Repnow, F. Schmitt, M. Steck, E. Steffens,1988 European Particle Accelera-tor Conference. Rome, vol.1, p.365.
[16]M Grieser, D.Habs, R.v.Hahn, C.M.Kleffner, R.Repnow, M.Stampfer,E.Jaeschke and M.Steck,1991 IEEE Particle Accelerator Conference, San Francisco,vol.5,p.2817
[17]H. Danared,Electron cooling at CRYRING,Phys. Scr.48,405 (1993).
[18]S.Datz and M. Larsson,Radiative lifetimes for all vibrational levels in the X 1∑+ state of HeH+ and its relevance to dissociative recombination experiments in ion storage rings,Phys. Scr.46 (1992)343.
[19]Hangst, J.S.; et al. (1992). "Laser cooling of stored ions in ASTRID:A storage ring for ions and electrons". Nuclear Instruments and Methods in Physics Research Section B 68: 17.Bibcode:1992NIMPB..68...17H.doi:10.1016/0168-583X(92)96042-W.
[20]"Beamlines on ASTRID". Institute for Storage Ring Facilities.13 June 2009. Retrieved 2012-04-01.
[21]Florescu-Mitchell A I,Mitchell J B A.Phys Rep,2006,430:277.
[22]蔡晓红,于得洋,杨建成,等.原子核物理评论,2010,27(3)：164CAI Xiao-hong, YU Deyang,YANG Jiancheng,Nuclear Physics Review,2010,27(3):164(in Chinese)
[15]Xia J W, Rao Y N, Yuan YJ, et al. HIRFL-CSR PLAN, The 6th China-Japan Joint Symposium on Accelerators for Nuclear Science and Their Applications,1996.10, Chengdu, China, P24—27
[16]Xia J W, Zhan W L, Wei B W, et al. The Heavy Ion Cooler-storage-Ring Project (HIRFL-CSR) at Lanzhou. NMA,2002,488:11—25
[25]詹文龙,魏宝文,等.兰州重离子冷却储存环[J].原子核物理评论,2001,18(1)：35236.(Xia J W, Zhan W L, Wei BW, et al. HIRFL-CSR heavy ion research facility. Nuclear Physics Review,2001,18(1):35236)
[26]陈佳洱主编,加速器物理基础,原于能出版社,1993
[27]王书鸿,罗紫华和罗应雄著,质子直线加速器原理,原子能出版社,1986
[28]桂伟燮,荷电粒子加速器原理,清华大学出版社(第一版),1994：169。
[29]孙别和,夏佳文.强流离子束的束包络方程与束包络计算.兰州大学学报(自然科学版),1990,26(4)：55
[30]"Handbook of ion sources" Bernhard Wolf (Ed.) (1995).
[31]SUN Liang-Ting,LI Jin-Yu,et ai Commission Test of LAPECR2 Source on the 320kV HV Platform.HICH ENERGY PHYSICS AND NUCLEAR PHYSICS.2007,31(1) 55-59
[32]姚泽恩,苏桐龄,姜汴婴.核技术,1992,15(12)：731-734YAO Zeen, SU Tongling, JIANG Bianying. Nucl Tech,1992,15(12):731-734
[33]苏桐龄,强流中子发生器及其应用,核技术,12(8,9)1989：553-556.
[34]姚泽恩,强磁透镜的物理设计报告,1997年(内部资料)
[35]姚泽恩,刘国汉,贾文宝,苏桐龄,董明义,磁镜场空间电荷透镜初步研究,甘肃科学：,Vol.13,No.3,2001：59-63.
[36]Zeen Yao, Tongling Su, Shang wen Cheng, et al. Design status of an intense 14MeV neutron source for cancer therapy[J]. Nuclear Instruments and Methods in Physics Research A,2002,490 (3):566-572.
[37]姚泽恩,苏桐龄,陈尚文等.用于治疗癌症的强流中子发生器束流光路设计[J].兰州大学学报(n然利·学版),2000,36(1)：28-33.Yao Zeen, Su Tongling, Chen Shangwen, et al. Beam Optics of Intense Neutron Generator for Cancer Therapy [J]. Journal of Lanzhou University (Natural Science),2000,36 (1):28-33.
[38]PIAO Yubo,LI Gongping,QIAN Defeng,et al.A space charge lens consisting of negative electrode and magnetic mirror [J].Atomic Energy Science and Technology,1990,42(2):1-6(in Chinese).(朴禹伯,李公平,钱德丰,等.一种由负电极和磁透镜组成的空间电荷透镜[J].原子能科学技术,1990,42(2)：1-6.)
[39]郁庆长,强流带电粒子束的传输矩阵理论,核技术,10(4)1987：38