MHz频率电子束束流动力学及其尾场效应研究
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摘要
多脉冲强流电子直线感应加速器(LIA)能够进行多幅闪光X射线照相,是发展先进的闪光X射线照相技术的重要研究课题。为了保证强流电子束的束流品质和多幅闪光X射线照相的图像质量,有必要开展MHz重复频率(多脉冲束流间隔<1μs)强流电子束束流动力学的研究。中国工程物理研究院与清华大学联合研制的小型双脉冲直线感应加速器——“明亮”加速器(Mini-LIA),为开展强流多脉冲LIA束流动力学研究和解决某些局部关键技术问题创造了条件。
论文分析了影响加速器束流输运的主要动力学因素,包括空间电荷效应、束质心螺旋运动和尾场效应的起因及其对强流束输运的影响方式和作用结果,得出了多脉冲强流束束流动力学的研究重点是多脉冲束团之间的尾场作用和束流传输过程中的束流崩溃不稳定性(BBU)效应随传输距离的增长现象。论文还研究了直线感应加速器加速间隙中尾场的产生、衰减及其对多脉冲强流束传输的影响。编写了Minienvelope程序,对单脉冲束流在Mini-LIA输运过程中的束包络进行了计算,并采用PARMELA程序对束团的束质心运动进行了模拟。
论文采用CST微波工作室程序对加速腔空心腔和磁芯腔两种结构进行了数值模拟计算,得到了腔中部分TM模式的频率及其纵向特性阻抗R/Q值。建立了加速腔高次模特性参数测量平台,用实验的方法对空心腔和磁芯腔中的TM模式的电磁场进行了辨别与确认,并测量了腔中相应模式的谐振频率和品质因数Q。推导了采用二极模(TM1n0模)的纵向特性阻抗来计算其横向阻抗的公式,计算出了空心腔和金属玻璃磁芯腔TM_(110)模的横向阻抗。
论文系统研究了测量LIA加速腔横向阻抗的同轴双线η因子法,建立了基于矢量网络分析仪的Mini-LIA加速腔横向阻抗测量平台,实验测量了空心腔和金属玻璃磁芯腔中TM_(110)模式的η因子和横向阻抗,取得了与模拟计算相符合的结果,为低Q值感应加速器横向阻抗的测量提供了一种实用的方法。论文最后分析了η因子法测量横向阻抗产生误差的多种原因,并结合模拟计算结果提出了相应的修正误差的方法。
论文工作对正在进行的新型LIA的研制具有一定的借鉴意义。
It is necessary for advanced X-ray flash radiography to develop linear induction accelerator (LIA) with multi-pulse high-current electron beam because of its multi-flash imaging technology. For needs of good quality of MHz repetition rate (pulse interval less than 1μs) high-current electron beam and multi-flash X-ray imaging, it is important to initiate beam dynamics research. A miniature double-pulse LIA (Mini-LIA) was constructed by CAEP and Tsinghua University in order that multi-pulse high-current beam dynamics is studied and parts of some new key techniques are preliminarily tested on it.
Three main dynamics factors——space charge effect, corkscrew and wake field effect influencing high-current beam transportation are compared and contrasted from their physical origins to their deteriorations on the beam. It is pointed out that the emphases of multi-pulse high-current beam dynamics are wake field effect produced among multi-bunch and cumulative beam breakup instability in beam transportation. Decay of wake field generated in LIA accelerating gap and its influence on multi-pulse high-current transportation are analyzed in this paper. A code named Minienvelope is written to simulate beam envelope changes of single-pulse beam moved on Mini-LIA and the variation of beam centroid is simulated by using PARMELA code.
By using CST microwave studio code, two structures of LIA cavity——empty cavity and metglas cavity are simulated respectively, and the resonant frequencies of several TM electromagnetic modes in two kinds of cavity as well as their corresponding longitudinal characteristic impedances R/Q are obtained. A bench measurement system is constructed for investigating characteristics of higher order modes (HOM) in Mini-LIA cavity. Discerning and confirmation of TM electromagnetic modes in two cavities are performed, and several TM modes in two cavities as well as their corresponding quality factors are achieved. The transverse impedances of two kinds of cavity are calculated by using a formula deriving from longitudinal characteristic impedances of dipole mode (TM1n0 mode).
This paper describes the principle, method, and techniques of transverse impedance measurement through coaxial twin-lead (ηfactor method). A bench measurement system based on vector network analyzer is constructed for transverse impedance measuring of Mini-LIA cavity. Theηfactors and transverse impedances of TM_(110) mode in two kinds of cavity are measured by experiment, and the result is consistent with the calculated one. A practical technique of transverse impedance measuring of LIA cavity with low Q is available. At last, analysis to several kinds of measuring error in transverse impedance measurement method withηfactor is performed and methods to correct the errors are discussed in this paper according to simulation result.
论文分析了影响加速器束流输运的主要动力学因素,包括空间电荷效应、束质心螺旋运动和尾场效应的起因及其对强流束输运的影响方式和作用结果,得出了多脉冲强流束束流动力学的研究重点是多脉冲束团之间的尾场作用和束流传输过程中的束流崩溃不稳定性(BBU)效应随传输距离的增长现象。论文还研究了直线感应加速器加速间隙中尾场的产生、衰减及其对多脉冲强流束传输的影响。编写了Minienvelope程序,对单脉冲束流在Mini-LIA输运过程中的束包络进行了计算,并采用PARMELA程序对束团的束质心运动进行了模拟。
论文采用CST微波工作室程序对加速腔空心腔和磁芯腔两种结构进行了数值模拟计算,得到了腔中部分TM模式的频率及其纵向特性阻抗R/Q值。建立了加速腔高次模特性参数测量平台,用实验的方法对空心腔和磁芯腔中的TM模式的电磁场进行了辨别与确认,并测量了腔中相应模式的谐振频率和品质因数Q。推导了采用二极模(TM1n0模)的纵向特性阻抗来计算其横向阻抗的公式,计算出了空心腔和金属玻璃磁芯腔TM_(110)模的横向阻抗。
论文系统研究了测量LIA加速腔横向阻抗的同轴双线η因子法,建立了基于矢量网络分析仪的Mini-LIA加速腔横向阻抗测量平台,实验测量了空心腔和金属玻璃磁芯腔中TM_(110)模式的η因子和横向阻抗,取得了与模拟计算相符合的结果,为低Q值感应加速器横向阻抗的测量提供了一种实用的方法。论文最后分析了η因子法测量横向阻抗产生误差的多种原因,并结合模拟计算结果提出了相应的修正误差的方法。
论文工作对正在进行的新型LIA的研制具有一定的借鉴意义。
It is necessary for advanced X-ray flash radiography to develop linear induction accelerator (LIA) with multi-pulse high-current electron beam because of its multi-flash imaging technology. For needs of good quality of MHz repetition rate (pulse interval less than 1μs) high-current electron beam and multi-flash X-ray imaging, it is important to initiate beam dynamics research. A miniature double-pulse LIA (Mini-LIA) was constructed by CAEP and Tsinghua University in order that multi-pulse high-current beam dynamics is studied and parts of some new key techniques are preliminarily tested on it.
Three main dynamics factors——space charge effect, corkscrew and wake field effect influencing high-current beam transportation are compared and contrasted from their physical origins to their deteriorations on the beam. It is pointed out that the emphases of multi-pulse high-current beam dynamics are wake field effect produced among multi-bunch and cumulative beam breakup instability in beam transportation. Decay of wake field generated in LIA accelerating gap and its influence on multi-pulse high-current transportation are analyzed in this paper. A code named Minienvelope is written to simulate beam envelope changes of single-pulse beam moved on Mini-LIA and the variation of beam centroid is simulated by using PARMELA code.
By using CST microwave studio code, two structures of LIA cavity——empty cavity and metglas cavity are simulated respectively, and the resonant frequencies of several TM electromagnetic modes in two kinds of cavity as well as their corresponding longitudinal characteristic impedances R/Q are obtained. A bench measurement system is constructed for investigating characteristics of higher order modes (HOM) in Mini-LIA cavity. Discerning and confirmation of TM electromagnetic modes in two cavities are performed, and several TM modes in two cavities as well as their corresponding quality factors are achieved. The transverse impedances of two kinds of cavity are calculated by using a formula deriving from longitudinal characteristic impedances of dipole mode (TM1n0 mode).
This paper describes the principle, method, and techniques of transverse impedance measurement through coaxial twin-lead (ηfactor method). A bench measurement system based on vector network analyzer is constructed for transverse impedance measuring of Mini-LIA cavity. Theηfactors and transverse impedances of TM_(110) mode in two kinds of cavity are measured by experiment, and the result is consistent with the calculated one. A practical technique of transverse impedance measuring of LIA cavity with low Q is available. At last, analysis to several kinds of measuring error in transverse impedance measurement method withηfactor is performed and methods to correct the errors are discussed in this paper according to simulation result.
引文
[1] J. DE Mascureau. et al.感应加速器的技术发展.杨凯旋译自CHOCS, Mumero 18, Mars 1998.
[2] Daniel Birx. INDUCTION LINEAR ACCELERATORS. 1992 American Institute of Physics.
[3] Richard J. Briggs. High current electron linacs (Advanced test accelerator/experimental test accelerator). DE84 012320.
[4] Mike Ong. et al. LLNL Flash X-ray Radiography Machine (FXR). 78-16-c, 1978.
[5] V.S. Bosamylrjn. et al. Linear Induction Accelerator LIA-10M. Proc. of PPC 1993, Albuquerque, IEEE, 1989.
[6]程念安等. 3.3MeV LIA研究与性能.强激光与粒子束, Vol. 4, No.3, 1992.
[7] J.Kishiro. et al. An Induction Linac and Pulse Power System at KEK. Proc.of the Particle Accelerator Conf., Washington 1993, IEEE, 1993: 673.
[8] Burns M. J. et al. Technology Demonstration for the DARHT Linear Induction Accelerator. Proceedings of International Conference on High Power Particle Beams, 1992: 283.
[9] J. DE Mascureau. et al. Design and Progress of the AIRIX Induction Accelerator. Proc. of the Particle Accelerator Conf. , Washington 1993, IEEE, 1993: 697.
[10]丁伯南等.“神龙一号”直线感应电子加速器.高能物理与核物理, 2005, 29(6).
[11] Burns M. J. et al. Status of the DARHT Phase 2 Long-Pulse Accelerator. Proceedings of the 2001 Particle Accelerator Conference, Chicago, U. S. A., 2001.
[12] Carl Ekdahl. et al. Commissioning the DARHT-II Scaled Accelerator. Proceedings of the 2007 Particle Accelerator Conference, Albuquerque, New Mexico, U. S. A, 2007.
[13] Y. J. (Judy) Chen. et al. Precision fast kickers for kiloampere electron beams. Proceedings of the 1999 Particle Accelerator Conference, New York, 1999.
[14] Cheng C. et al. An Introduction to Mini-LIA. Proceedings of the 17th International Conference on High-Power Particle Beams, Xi'an, China, 2008.
[15]荆晓兵等. 200 keV LIA研制总结报告. 2009.
[16] Vlasov A A. J Phys USSR. 9, 25, 1945.
[17] Graybill S. E. et al. IEEE Trans Nucl Sci. NS14, 782, 1967.
[18]刘锡三.强流粒子束及其应用.国防工业出版社, 2007.
[19] R. D. Scarpetti. et al. Status of the DARHT 2nd Axis Accelerator at Los Alamos National Laboratory. Proceedings of the 2007 Particle Accelerator Conference, Albuquerque, New Mexico, U. S. A, 2007.
[20] Barnard J.J., et al. Progress in Heavy Ion Driven Inertial Fusion Energy: From Scaled Experiments to the Integrated Research Experiment, Proceedings of the 2001 Particle Accelerator Conference, Chicago, U. S. A., 2001.
[21]惠钟锡等.曙光一号自由电子激光放大实验.强激光与粒子束, Vol.7, No.3, 1994.
[22] T.J.Fessenden et al. The experimental test accelerator (ETA) II. IEEE Transactions on Nuclear Science, 1981, 28(3).
[23] Septier A. Very-High-Density Beams. Applied Charged Particle Optics Part C Academic Press. 1983.
[24] Y. J. Chen. Corkscrew modes in linear accelerator. NIM in physics. A292, 455, 1990.
[25] Lau Y. and Brix D. L. Classification of BBU instabilities in linear accelerator. Phys. Rev. Lett. 63(11): 1141, 1989.
[26] Alexander Wu Zhao. Physics of Collective Beam Instabilities in High Energy Accelerators. John Wiley&Sons, Inc. , 1993.
[27] C. C. Shang. et al. BBU DESIGN OF LINEAR INDUCTION ACCELERATOR CELLS FOR RADIOGRAPHY APPLICATION, Proc. of the 1997 Particle Accelerator Conf., Vancouver, 1998, 2633
[28] W. M. Fawley (LBNL). et al. BEAM BREAKUP CALCULATIONS FOR THE SECOND AXIS OF DARHT. Proc. of the 1999 Particle Accelerator Conf., New York, 1999, 1210.
[29] Y. J. Chen. et al. BBU AND CORKSCREW GROWTH PREDICTIONS FOR THE DARHT SECOND AXIS ACCELERATOR. Proceedings of the 2001 Particle Accelerator Conference, Chicago, U. S. A, 2001, 3490.
[30] R. Briggs. et al. TRANSVERSE IMPEDANCE MEASUREMENTS OF THE DARHT-2 ACCELERATOR CELL. Proc. of the 2001 Particle Accelerator Conf., Chicago, U. S. A, 2001, 1850
[31] Michael Burns. et al. MAGNET DESIGN FOR THE DARHT LINEAR INDUCTION ACCELERATORS, Proc. of the 1991 Particle Accelerator Conf., San Francisco, 1991, 2110
[32] Carl Ekdahl. et al. DARHT-II LONG-PULSE BEAM DYNAMICS EXPERIMENTS. Proc. of the 2005 Particle Accelerator Conf., Tennessee, 2005, 19
[33]张开志等.直线感应加速器束流崩溃不稳定性数值模拟.强激光与粒子束,Vol. 15, No. 4, Apr. 2003: 398~401.
[34]李献文等.直线感应加速器束心偏移轨迹的计算.计算物理,Vol. 23, No. 4, July, 2006: 387~390.
[35]代志勇等.“神龙一号”加速器束流输运系统研制.高能物理与核物理,Vol. 31, No. 4, Apr. 2007: 395~399.
[36]石金水等.利用交变极性聚焦磁场抑制束质心的Corkscrew运动.核技术, Vol. 26, No. 3, March. 2003: 202~206.
[37]代志勇等. LIA注入器发射度增长机理研究及其抑制措施.高能物理与核物理, Vol. 28, No. 9, Sept., 2004: 1002~1006.
[38]章文卫等.强流直线感应加速腔微波特性.强激光与粒子束, Vol. 20, No. 12, Dec., 2008: 2073~2077.
[39]程皓.非晶材料在LIA中的应用研究.【硕士学位论文】,绵阳:中国工程物理研究院, 2002
[40]黄子平.铁氧体及金属玻璃的多脉冲磁特性研究.【硕士学位论文】,绵阳:中国工程物理研究院, 2002.
[41] M. V. Zumbro. et al. DARHT SECOND AXIS– STATUS AND PLANS. Proceedings of LINAC 2002, Gyeongju, Korea.
[42] M. Burns. et al. Technology Demonstration for the DARHT Linear Induction Accelerator. 11th IEEE International Pulsed Power Conference, June 29-July 2, 1997.
[43]罗应雄.带电粒子束的自场.科学技术文献出版社.北京, 1981.
[44]石金水.直线感应电子加速器中的Corkscrew运动及其抑制.【博士学位论文】,北京:清华大学工程物理系, 2001.
[45]张开志.直线感应电子加速器的束流崩溃不稳定性研究【.博士学位论文】,北京:清华大学工程物理系, 2000.
[46]代志勇.直线感应加速器束流发射度增长与抑制研究.【博士学位论文】,中国科学院研究生院, 2004.
[47]廖树清.双脉冲电子直线感应加速器实验研究.【博士学位论文】,北京:清华大学工程物理系, 2008.
[48]沈致远.微波技术.国防工业出版社,北京, 1980.
[49]施嘉儒.用于束流调控及诊断的高频偏转腔的研究.【博士学位论文】,北京:清华大学工程物理系, 2009.
[50]张敏. CST微波工作室用户全书(卷一&卷二).电子科技大学出版社,成都, 2004.
[51] Panofsky W. K. H. et al. Some Considerations Concerning the Transverse Deflection of Charged Particles in Radio-Frequency Fields. Rev. Sci. Instrum., 1956, 27: 967.
[52] R. J. Briggs. et al. Campaign to minimize the transverse impedance of the DARHT-2 induction linac cells. University of California, U. S. A, 2005.
[53] R. J. Briggs. et al. TRANSVERSE IMPEDANCE MEASUREMENTS OF THE DARHT-2 ACCELERATOR CELL. Proceedings of the 2001 Particle Accelerator Conference, Chicago. U. S. A, 2001.
[2] Daniel Birx. INDUCTION LINEAR ACCELERATORS. 1992 American Institute of Physics.
[3] Richard J. Briggs. High current electron linacs (Advanced test accelerator/experimental test accelerator). DE84 012320.
[4] Mike Ong. et al. LLNL Flash X-ray Radiography Machine (FXR). 78-16-c, 1978.
[5] V.S. Bosamylrjn. et al. Linear Induction Accelerator LIA-10M. Proc. of PPC 1993, Albuquerque, IEEE, 1989.
[6]程念安等. 3.3MeV LIA研究与性能.强激光与粒子束, Vol. 4, No.3, 1992.
[7] J.Kishiro. et al. An Induction Linac and Pulse Power System at KEK. Proc.of the Particle Accelerator Conf., Washington 1993, IEEE, 1993: 673.
[8] Burns M. J. et al. Technology Demonstration for the DARHT Linear Induction Accelerator. Proceedings of International Conference on High Power Particle Beams, 1992: 283.
[9] J. DE Mascureau. et al. Design and Progress of the AIRIX Induction Accelerator. Proc. of the Particle Accelerator Conf. , Washington 1993, IEEE, 1993: 697.
[10]丁伯南等.“神龙一号”直线感应电子加速器.高能物理与核物理, 2005, 29(6).
[11] Burns M. J. et al. Status of the DARHT Phase 2 Long-Pulse Accelerator. Proceedings of the 2001 Particle Accelerator Conference, Chicago, U. S. A., 2001.
[12] Carl Ekdahl. et al. Commissioning the DARHT-II Scaled Accelerator. Proceedings of the 2007 Particle Accelerator Conference, Albuquerque, New Mexico, U. S. A, 2007.
[13] Y. J. (Judy) Chen. et al. Precision fast kickers for kiloampere electron beams. Proceedings of the 1999 Particle Accelerator Conference, New York, 1999.
[14] Cheng C. et al. An Introduction to Mini-LIA. Proceedings of the 17th International Conference on High-Power Particle Beams, Xi'an, China, 2008.
[15]荆晓兵等. 200 keV LIA研制总结报告. 2009.
[16] Vlasov A A. J Phys USSR. 9, 25, 1945.
[17] Graybill S. E. et al. IEEE Trans Nucl Sci. NS14, 782, 1967.
[18]刘锡三.强流粒子束及其应用.国防工业出版社, 2007.
[19] R. D. Scarpetti. et al. Status of the DARHT 2nd Axis Accelerator at Los Alamos National Laboratory. Proceedings of the 2007 Particle Accelerator Conference, Albuquerque, New Mexico, U. S. A, 2007.
[20] Barnard J.J., et al. Progress in Heavy Ion Driven Inertial Fusion Energy: From Scaled Experiments to the Integrated Research Experiment, Proceedings of the 2001 Particle Accelerator Conference, Chicago, U. S. A., 2001.
[21]惠钟锡等.曙光一号自由电子激光放大实验.强激光与粒子束, Vol.7, No.3, 1994.
[22] T.J.Fessenden et al. The experimental test accelerator (ETA) II. IEEE Transactions on Nuclear Science, 1981, 28(3).
[23] Septier A. Very-High-Density Beams. Applied Charged Particle Optics Part C Academic Press. 1983.
[24] Y. J. Chen. Corkscrew modes in linear accelerator. NIM in physics. A292, 455, 1990.
[25] Lau Y. and Brix D. L. Classification of BBU instabilities in linear accelerator. Phys. Rev. Lett. 63(11): 1141, 1989.
[26] Alexander Wu Zhao. Physics of Collective Beam Instabilities in High Energy Accelerators. John Wiley&Sons, Inc. , 1993.
[27] C. C. Shang. et al. BBU DESIGN OF LINEAR INDUCTION ACCELERATOR CELLS FOR RADIOGRAPHY APPLICATION, Proc. of the 1997 Particle Accelerator Conf., Vancouver, 1998, 2633
[28] W. M. Fawley (LBNL). et al. BEAM BREAKUP CALCULATIONS FOR THE SECOND AXIS OF DARHT. Proc. of the 1999 Particle Accelerator Conf., New York, 1999, 1210.
[29] Y. J. Chen. et al. BBU AND CORKSCREW GROWTH PREDICTIONS FOR THE DARHT SECOND AXIS ACCELERATOR. Proceedings of the 2001 Particle Accelerator Conference, Chicago, U. S. A, 2001, 3490.
[30] R. Briggs. et al. TRANSVERSE IMPEDANCE MEASUREMENTS OF THE DARHT-2 ACCELERATOR CELL. Proc. of the 2001 Particle Accelerator Conf., Chicago, U. S. A, 2001, 1850
[31] Michael Burns. et al. MAGNET DESIGN FOR THE DARHT LINEAR INDUCTION ACCELERATORS, Proc. of the 1991 Particle Accelerator Conf., San Francisco, 1991, 2110
[32] Carl Ekdahl. et al. DARHT-II LONG-PULSE BEAM DYNAMICS EXPERIMENTS. Proc. of the 2005 Particle Accelerator Conf., Tennessee, 2005, 19
[33]张开志等.直线感应加速器束流崩溃不稳定性数值模拟.强激光与粒子束,Vol. 15, No. 4, Apr. 2003: 398~401.
[34]李献文等.直线感应加速器束心偏移轨迹的计算.计算物理,Vol. 23, No. 4, July, 2006: 387~390.
[35]代志勇等.“神龙一号”加速器束流输运系统研制.高能物理与核物理,Vol. 31, No. 4, Apr. 2007: 395~399.
[36]石金水等.利用交变极性聚焦磁场抑制束质心的Corkscrew运动.核技术, Vol. 26, No. 3, March. 2003: 202~206.
[37]代志勇等. LIA注入器发射度增长机理研究及其抑制措施.高能物理与核物理, Vol. 28, No. 9, Sept., 2004: 1002~1006.
[38]章文卫等.强流直线感应加速腔微波特性.强激光与粒子束, Vol. 20, No. 12, Dec., 2008: 2073~2077.
[39]程皓.非晶材料在LIA中的应用研究.【硕士学位论文】,绵阳:中国工程物理研究院, 2002
[40]黄子平.铁氧体及金属玻璃的多脉冲磁特性研究.【硕士学位论文】,绵阳:中国工程物理研究院, 2002.
[41] M. V. Zumbro. et al. DARHT SECOND AXIS– STATUS AND PLANS. Proceedings of LINAC 2002, Gyeongju, Korea.
[42] M. Burns. et al. Technology Demonstration for the DARHT Linear Induction Accelerator. 11th IEEE International Pulsed Power Conference, June 29-July 2, 1997.
[43]罗应雄.带电粒子束的自场.科学技术文献出版社.北京, 1981.
[44]石金水.直线感应电子加速器中的Corkscrew运动及其抑制.【博士学位论文】,北京:清华大学工程物理系, 2001.
[45]张开志.直线感应电子加速器的束流崩溃不稳定性研究【.博士学位论文】,北京:清华大学工程物理系, 2000.
[46]代志勇.直线感应加速器束流发射度增长与抑制研究.【博士学位论文】,中国科学院研究生院, 2004.
[47]廖树清.双脉冲电子直线感应加速器实验研究.【博士学位论文】,北京:清华大学工程物理系, 2008.
[48]沈致远.微波技术.国防工业出版社,北京, 1980.
[49]施嘉儒.用于束流调控及诊断的高频偏转腔的研究.【博士学位论文】,北京:清华大学工程物理系, 2009.
[50]张敏. CST微波工作室用户全书(卷一&卷二).电子科技大学出版社,成都, 2004.
[51] Panofsky W. K. H. et al. Some Considerations Concerning the Transverse Deflection of Charged Particles in Radio-Frequency Fields. Rev. Sci. Instrum., 1956, 27: 967.
[52] R. J. Briggs. et al. Campaign to minimize the transverse impedance of the DARHT-2 induction linac cells. University of California, U. S. A, 2005.
[53] R. J. Briggs. et al. TRANSVERSE IMPEDANCE MEASUREMENTS OF THE DARHT-2 ACCELERATOR CELL. Proceedings of the 2001 Particle Accelerator Conference, Chicago. U. S. A, 2001.