共查询到20条相似文献,搜索用时 15 毫秒
1.
Xiongwei Zhu 《International Journal of Infrared and Millimeter Waves》2004,25(4):667-671
The effect of high spatial harmonics on beam dynamics in a axisymmetric radio frequency linear accelerator (RF linac) is examined. The high spatial harmonics forms the second order ponderomotive focusing for the relativistical particle beam when the transverse motion is averaged over the period of RF structure, the beam transverse envelop equation is obtained including the ponderomotive focusing force which is useful for the design of RF gun and linac. Under a certain of high spatial harmonics coefficients, the high spatial harmonics increase the energy spread due to the stochasitical beam energy diffusion. 相似文献
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对于多束团运行的储存环,逐束团流强的测量是研究注入填充和束流不稳定性阈值等的重要内容。介绍了加速器常用的一些逐束团监测手段,在此基础上,利用HLS(Hefei Light Source)现有的逐束团测量设备,并配合相应前端信号处理电路,进行了HLS储存环逐束团流强测量。实验线路方面,在传统的高频频率倍频信号检波的基础上,尝试了新的与同步方波信号检波的方法。分别在多束团和单束团情况下对HLS的束团流强进行了连续检测实验,对实验结果进行线性拟合,得到了定标结果,结果表明系统的1阶线性拟合标准偏差均在1%左右;最后对其中非线性部分的物理本质进行了解释。 相似文献
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Muggli P Blue BE Clayton CE Decker FJ Hogan MJ Huang C Joshi C Katsouleas TC Lu W Mori WB O'Connell CL Siemann RH Walz D Zhou M 《Physical review letters》2008,101(5):055001
An ultrarelativistic 28.5 GeV, 700-microm-long positron bunch is focused near the entrance of a 1.4-m-long plasma with a density n(e) between approximately equal to 10(13) and approximately equal to 5 x 10(14) cm(-3). Partial neutralization of the bunch space charge by the mobile plasma electrons results in a reduction in transverse size by a factor of approximately equal to 3 in the high emittance plane of the beam approximately equal to 1 m downstream from the plasma exit. As n(e) increases, the formation of a beam halo containing approximately 40% of the total charge is observed, indicating that the plasma focusing force is nonlinear. Numerical simulations confirm these observations. The bunch with an incoming transverse size ratio of approximately 3 and emittance ratio of approximately 5 suffers emittance growth and exits the plasma with approximately equal sizes and emittances. 相似文献
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M. Kando Y. Fukuda H. Kotaki J. Koga S. V. Bulanov T. Tajima A. Chao R. Pitthan K. -P. Schuler A. G. Zhidkov K. Nemoto 《Journal of Experimental and Theoretical Physics》2007,105(5):916-926
We suggest a novel method for the injection of electrons into the acceleration phase of particle accelerators, producing low-emittance
beams appropriate even for the demanding high-energy linear collider specifications. We discuss the injection mechanism into
the acceleration phase of the wakefield in a plasma behind a high-intensity laser pulse, which takes advantage of the laser
polarization and focusing. The scheme uses the structurally stable regime of transverse wakewave breaking, when the electron
trajectory self-intersection leads to the formation of a flat electron bunch. As shown in three-dimensional particle-in-cell
simulations of the interaction of a laser pulse elongated in the transverse direction with an underdense plasma, the electrons
injected via the transverse wakewave breaking and accelerated by the wakewave perform betatron oscillations with different
amplitudes and frequencies along the two transverse coordinates. The polarization and focusing geometry lead to a way to produce
relativistic electron bunches with an asymmetric emittance (flat beam). An approach for generating flat laser-accelerated
ion beams is briefly discussed.
The text was submitted by the authors in English. 相似文献
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We propose and analyze a scheme to produce comb bunches, i.e. a bunch consisting of micro-bunch trains, with tunable subpicosecond spacing. In the scheme, the electron beam is first deflected by a deflecting cavity which introduces a longitudinal-dependent linear transverse kick to the particles. After passing through a drift space, the transverse beam size is linearly coupled to the longitudinal position of the particle inside the beam, and a mask is placed there to tailor the beam, then the mask distribution is imprinted on the beam's longitudinal distribution. A quadrupole magnet and another deflecting cavity are used in the beam line to compensate the transverse angle due to the first deflecting cavity. Analysis shows that the number, length, and spacing of the trains can be controlled through the parameters of the deflecting cavity and the mask. Such electron bunch trains can be applied to an infrared free electron laser, a plasma-wakefield accelerator and a supper-radiance THz source. 相似文献
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A particle-in-cell mode beam dynamics simulation of medium energy beam transport for the SSC-Linac 总被引:1,自引:0,他引:1
A new linear accelerator system, called the SSC-Linac injector, is being designed at HIRFL (the heavy ion research facility of Lanzhou). As part of the SSC-Linac, the medium energy beam transport (MEBT) consists of seven magnetic quadrupoles, a re-buncher and a diagnose box. The total length of this segment is about 1.75 m. The beam dynamics simulation in MEBT has been studied using the TRACK 3D particle-in-cell code, and the simulation result shows that the beam accelerated from the radio frequency quadrupole (RFQ) matches well with the acceptance of the following drift tube linac (DTL) in both the transverse and longitudinal phase spaces, and that most of the particles can be captured by the final sector focusing cyclotron for further acceleration. The longitudinal emittance of the RFQ and the longitudinal acceptance of the DTL was calculated in detail, and a multi-particle beam dynamics simulation from the ion source to the end of the DTL was done to verify the original design. 相似文献
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Held only weeks after the SRS had delivered its last photon beams (from September 11?12, 2008), the 2008 UK Synchrotron Radiation User Meeting was a mixture of nostalgia, news and next steps. Prof. Chris Hardacre, Chairman of the User Forum, welcomed everyone to the meeting and opened the session reserved for updates from the sources mostly used by the UK community. Dr. Tracy Turner began by showing a short video clip of the last seconds of multibunch user beam at the official SRS switch off ceremony on August 4. Highlighting several recent results to illustrate the point, she described how the SRS had been productive right up to the end with a late surge in operational reliability in both multibunch and single bunch modes. Over 400 papers have already been published this year, and many of these in high impact factor journals. She announced the imminent publication of the final Annual Report and a survey of the economic impact made by the SRS over its lifetime which had been prompted by the impending closure and which will be informative to government and other bodies in assessing the benefits that accrue from investment in large-scale facilities. 相似文献
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Absorption of an intense short laser pulse by targets consisting of a bungle of carbon nanofilaments either parallel or converging to the vertex of a cone has been numerically simulated. Such targets efficiently generate a flux of relativistic electrons propagating along filaments and following their bends. The focusing of fluxes from several filaments to one flux makes it possible to reduce the transverse size of an electron bunch as compared to the diameter of the laser beam. The energy flux density of electrons in such a bunch propagating along one nanofilament is several times higher than the energy flux density of the laser pulse. 相似文献
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V. M. Zhabitsky 《Physics of Particles and Nuclei Letters》2012,9(4-5):337-341
The beam stability problem in synchrotrons with a digital transverse feedback system (TFS) is studied. The TFS damper kicker (DK) corrects the transverse momentum of a bunch in proportion to its displacement from the closed orbit measured at the location of the beam position monitor (BPM). It is shown that the area and configuration of the beam stability separatrix depend on the beam tune, the feedback gain, the phase balance between the phase advance from BPM to DK and the phase response of the feedback chain at the betatron frequency. 相似文献
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ZHANG Jing-Ru DAI Jian-Ping GU Qiang PEI Guo-Xi ZHAO Ming-Hua ZHONG Shao-Peng WANG Xing-Tao CHEN Yong-Zhong HOU Mi 《中国物理C(英文版)》2010,34(1):138-142
RF deflectors can be used for bunch length measurement with high resolution. This paper describes a completed S-band traveling wave RF deflector and the bunch length measurement of the electron beam produced by the photocathode RF gun of the Shanghai DUV-FEL facility. This is the first time that such a transverse RF deflector has been developed and used to measure the bunch length of picosecond order in China. The deflector's VSWR is 1.06, the whole attenuation 0.5 dB, and the bandwidth 4.77 MHz for VSWR less than 1.1. With a laser pulse width of 8.5 ps, beam energy of 4.2 MeV, and bunch charge of 0.64 nC, the bunch lengths for different RF input power into the deflector were measured, and an averaged rms bunch length of 5.25 ps was obtained. A YAG crystal is used as a screen downstream of the deflector, with the calibrated value of 1 pix = 136 μm. 相似文献
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介绍了在合肥光源开展逐束团测量(横向和纵向)和横向束流反馈系统研究和研制的重要性,同时还介绍了设计思想。合肥光源高频频率为204 MHz,因此,系统至少需要100 MHz的带宽。还较详细地介绍了宽带部件和系统参数的选择原则。该系统不仅可用于研究由于高频腔中的高阶模和真空室的阻抗壁效应所引起的耦合束团不稳定性,而且还能抑制耦合束团不稳定性振荡、快速束流离子不稳定性和注入大幅度振荡等,从而将提高机器的运行性能。 相似文献
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In this paper we present a technique to optimize the transport parameters for transverse matching of the space charge dominated beams in the presence of bunching. The increase in the current within the specified bunch width during the transport is obtained from the disc model and is included in the optimization method. A 2D particle in cell (PIC) code is then developed to study the details transverse dynamics of the bunch taking into account the effect of longitudinal compression by reweighting the charge and mass of macroparticles. The evolution of rms beam size obtained using PIC simulation agrees well with the results obtained by solving beam envelope equation. The PIC simulation shows emittance growth during bunching induced by the space charge effect for nonuniform distribution. The growth in the emittance increases with the nonlinearity of distribution and peaks near the time focus. 相似文献
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空间电荷效应是引起发射度增长的主要因素,特别是在高压直流连续波光阴极注入器中。分析了高压直流连续波光阴极注入器中线性空间电荷力的特点及其对电子束横向发射度的影响,并从理论上解析地研究了螺线管发射度补偿的原理及特点。最后利用Parmela程序对中国工程物理研究院高压直流连续波光阴极注入器的发射度补偿作了模拟计算。结果表明,束团电荷量为80 pC的电子束在350 keV高压直流电子枪出口处的横向归一化发射度为5.14 mmmrad,经过螺线管补偿后,其最小横向发射度变为1.27 mmmrad。电子束的发射度得到了很好的补偿。 相似文献
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模拟研究了1.6个腔、高梯度的W-band光阴极微波电子枪系统,该系统能产生和加速300pC的电子束团.设计系统由频率91.392GHz光阴极微波电子枪以及频率91.392GHz行波加速结构组成.基于射频直线加速器标度律与数值模拟结果,设计系统能产生能量1.74MeV,电量300pC,束团长度0.72ps,归一化横向发射度0.55mm·mrad的电子束团.研究了高频、高梯度下的束流动力学.由于高梯度,有质动力效应在束流动力学中起重要作用,且由于横向与纵向之间的耦合,在基次空间谐波的情形下,仍然存在着有质动力聚焦效应. 相似文献
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V. M. Zhabitsky 《Physics of Particles and Nuclei Letters》2013,10(1):74-80
The transient beam response to an external impulse force in synchrotrons with a digital transverse feedback system is studied. The experimental data on damping coherent transverse oscillations of bunch excited by a discrete-time unit impulse in the Large Hadron Collider (LHC) are analyzed. Good agreement between the measured and theoretically predicted decrements has been obtained. A method of feedback fine tuning based on measurements of the bunch response to a harmonic excitation impulse is discussed. 相似文献