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Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366)最新文献

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Multipacting study of the RF window at the Advanced Photon Source 先进光子源下射频窗口的多作用研究
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.795356
J.J. Song
Multipacting current can cause breakdowns in high power RF components such as input couplers, waveguide windows, and higher-order mode (HOM) dampers. To understand and prevent the loss of a ceramic window or an input coupler in the Advanced Photon Source (APS) storage ring RF cavity, the multipacting phenomenon is being investigated experimentally. This paper begins with a description of simple model, presents a hardware design, and concludes with measurement of multipacting. Multipacting is explored in conjunction with conditioning the cavities and interaction with the stored beam.
多击电流可能导致高功率射频元件(如输入耦合器、波导窗口和高阶模式(HOM)阻尼器)击穿。为了了解和防止在先进光子源(APS)存储环射频腔中陶瓷窗口或输入耦合器的损耗,实验研究了多重冲击现象。本文从简单的模型描述开始,给出了硬件设计,最后给出了多处理机的测量。结合腔体的调节和与存储光束的相互作用,探讨了多重效应。
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引用次数: 2
Calculations of the self-amplified spontaneous emission performance of a free-electron laser 自由电子激光器自放大自发发射性能的计算
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.792742
R. Dejus, O. Shevchenko, N. Vinokurov
The linear integral equation based computer code (RON: "Roger Oleg Nikolai"), which was recently developed at Argonne National Laboratory, was used to calculate the self-amplified spontaneous emission (SASE) performance of the free-electron laser (FEL) being built at Argonne. Signal growth calculations under different conditions are used for estimating tolerances of actual design parameters. The radiation characteristics are discussed, and calculations using an ideal undulator magnetic field and a real measured magnetic field will be compared and discussed.
最近由阿贡国家实验室开发的基于线性积分方程的计算机代码(RON:“Roger Oleg Nikolai”)被用于计算阿贡国家实验室正在建造的自由电子激光器(FEL)的自放大自发发射(SASE)性能。利用不同条件下的信号增长计算来估计实际设计参数的公差。讨论了其辐射特性,并对理想波动磁场和实际测量磁场的计算结果进行了比较和讨论。
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引用次数: 3
Simultaneous measurement of electron beam size and divergence with an undulator 用波动器同时测量电子束大小和散度
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.794406
B. Yang, A. Lumpkin
We present the simultaneous measurement of beam divergence and source size based on the APS diagnostic undulator line. A 300-/spl mu/m-thick Si(400) crystal monochromator is used to measure the divergence with a resolution down to 3 /spl mu/rad (1 /spl mu/rad with the third harmonic). X-rays transmitted through the crystal are simultaneously used by a pinhole camera to measure the beam size, at a resolution of about 40 /spl mu/m. We demonstrate that this measurement of emittance is robust against fluctuations of lattice functions due to a partial cancellation of systematic errors present in each of the measurements.
本文提出了基于APS诊断波动线的光束发散度和源尺寸的同时测量方法。使用300-/spl mu/m厚的Si(400)晶体单色仪测量散度,分辨率低至3 /spl mu/rad(三次谐波为1 /spl mu/rad)。通过晶体传输的x射线同时被针孔相机用来测量光束的大小,分辨率约为40 /spl mu/m。我们证明,由于每个测量中存在的系统误差部分抵消,这种发射度测量对晶格函数的波动具有鲁棒性。
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引用次数: 6
Commissioning results of the narrow-band beam position monitor system upgrade in the APS storage ring APS存储环窄带波束位置监测系统升级调试结果
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.794383
O. Singh, C. Doose, J. Carwardine, G. Decker, F. Lenkszus, R. Merl
When using a low emittance storage ring as a high brightness synchrotron radiation source, it is critical to maintain a very high degree of orbit stability, both for the short term and for the duration of an operational fill. A fill-to-fill reproducibility is an additional important requirement. Recent developments in orbit correction algorithms have provided tools that are capable of achieving a high degree of orbit stability. However, the performance of these feedback systems can be severely limited if there are errors in the beam position monitors (BPMs). The present orbit measurement and correction system at the APS storage ring utilizes 360 broadband-type BPMs that provide turn-by-turn diagnostics and an ultra-stable orbit: <1.8 micron rms vertically and 4.5 microns rms horizontally in a frequency band of 0.017 to 30 Hz. The effects of beam intensity and bunch pattern dependency on these BPMs have been significantly reduced by employing "offset compensation" correction. Recently, 40 narrow-band switching-type BPMs have been installed in the APS storage ring, two in each of 20 operational insertion device straight sections, bringing the total number of beam position monitors to 400. The use of narrow-band BPM electronics is expected to reduce sensitivity to beam intensity, bunch pattern dependence, and long-term drift. These beam position monitors are used for orbit correction/feedback and machine protection interlocks for the insertion device beamlines. The commissioning results and overall performance for orbit stability are provided.
当使用低发射度存储环作为高亮度同步辐射源时,无论是在短期还是在操作填充期间,保持非常高的轨道稳定性都是至关重要的。填充到填充的再现性是另一个重要的要求。轨道校正算法的最新发展提供了能够实现高度轨道稳定性的工具。然而,如果波束位置监测器(bpm)存在误差,这些反馈系统的性能将受到严重限制。目前在APS存储环上的轨道测量和校正系统利用360个宽带型bpm,提供轮流诊断和超稳定的轨道:在0.017至30 Hz的频段内垂直<1.8微米rms,水平< 4.5微米rms。通过采用“偏移补偿”校正,可以显著降低光束强度和束束模式依赖对这些bpm的影响。最近,在APS存储环中安装了40个窄带开关型bpm,每20个操作插入设备直段各安装两个,使波束位置监视器的总数达到400个。使用窄带BPM电子器件有望降低对光束强度、束模式依赖和长期漂移的灵敏度。这些波束位置监测器用于轨道校正/反馈和插入装置波束线的机器保护联锁。给出了调试结果和轨道稳定总体性能。
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引用次数: 2
The APS SASE FEL: modeling and code comparison APS SASE FEL:建模和代码比较
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.792740
S.G. Biedrou, Y. Chae, R. Dejus, B. Faatz, H. Freund, S. Milton, H. Nuhn, S. Reiche
A self-amplified spontaneous emission (SASE) free-electron laser (FEL) is under construction at the Advanced Photon Source (APS). Five FEL simulation codes were used in the design phase: GENESIS, GINGER, MEDUSA, RON, and TDA3D. Initial comparisons between each of these independent formulations show good agreement for the parameters of the APS SASE FEL.
先进光子源(APS)正在建设自放大自发发射(SASE)自由电子激光器(FEL)。设计阶段使用了GENESIS、GINGER、MEDUSA、RON和TDA3D五种自由电子激光器仿真代码。这些独立公式之间的初步比较表明,APS SASE FEL的参数具有良好的一致性。
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引用次数: 12
Numerical studies of a second harmonic RF cavity for the IPNS RCS IPNS RCS中二次谐波射频腔的数值研究
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.792657
J. Dooling, F. Brumwell, G. Mcmichael, M. Middendorf, R. Zolecki
The Intense Pulsed Neutron Source (IPNS) Rapid Cycling Synchrotron (RCS) delivers 450-MeV protons in 70 ns pulses at 30 Hz to a heavy-metal target producing spallation neutrons for material science research. The average current extracted from the RCS is 15 /spl mu/A with a peak intensity of 10 amps. The large circulating currents in the RCS generate oscillations in the bunch which are presently controlled by modulating the phase of the two RF cavities. By adding second harmonic (SH) rf, the bunch length can be increased reducing the peak current. Simulations suggest that a 20-40 percent increase in extracted current should be achievable. The simulation program allows for phasing between fundamental and SH RF voltages. Initial studies to optimize phase indicate the need to maximize bucket area early in the acceleration cycle, whereas the bunching factor is more significant later in the cycle.
强脉冲中子源(IPNS)快速循环同步加速器(RCS)以70 ns 30 Hz的脉冲向重金属靶发射450-MeV的质子,产生散裂中子,用于材料科学研究。从RCS提取的平均电流为15 /spl mu/A,峰值强度为10安培。RCS中的大循环电流在束中产生振荡,目前通过调制两个射频腔的相位来控制振荡。通过增加二次谐波(SH)射频,可以增加束长,减小峰值电流。模拟表明,提取电流增加20- 40%是可以实现的。该仿真程序允许在基频和低频电压之间进行分相。优化相位的初步研究表明,需要在加速周期的早期最大化铲斗面积,而在周期的后期,聚束系数更为显著。
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引用次数: 4
Observations of "effective" transverse beam-size instabilities for a high current per bunch fill pattern in the APS storage ring APS存储环中每束高电流填充模式的“有效”横向波束尺寸不稳定性观察
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.794398
A. Lumpkin, L. Emery, B. Yang
The X-ray pinhole camera diagnostics on the Advanced Photon Source (APS) storage ring have recorded an "effective" transverse beam size instability during operations with a sextuplet plus 22 singlets fill pattern. These instabilities were not observed with the sextuplet plus 25 triplets fill pattern that has been the standard fill pattern in FY'98. The instability threshold is at 82-85 mA with positrons. The features include an increased average (few seconds) transverse size both horizontally anti vertically for stored currents above the threshold with a correlated effect on the beam lifetime. The horizontal transverse emittance is 25-30% larger at 100 mA than below the threshold. There is a related horizontal beam centroid motion as well, but this does not explain the vertical size change nor the lifetime effect. Complementary data were also taken with the diagnostic undulator, and a similar threshold effect on divergence was observed. The cross-comparison of the data and possible mechanisms are presented.
在先进光子源(APS)存储环上的x射线针孔相机诊断记录了在六重态加22个单重态填充模式下的“有效”横向光束尺寸不稳定性。这些不稳定性在1998年标准的六联体加25三联体填充模式中没有观察到。带正电子的不稳定阈值为82 ~ 85 mA。其特点包括增加平均(几秒)横向尺寸水平和垂直存储电流高于阈值与光束寿命相关的影响。水平横向发射度在100 mA时比低于阈值时大25-30%。也有一个相关的水平梁质心运动,但这并不能解释垂直尺寸的变化,也不能解释寿命效应。补充数据也与诊断波动器,并观察到类似的阈值效应发散。提出了数据的交叉比较和可能的机制。
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引用次数: 2
Improved temperature regulation and corrosion protection of APS linac RF components 改进了APS直线射频元件的温度调节和腐蚀保护
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.795566
M. White, R. Dortwegt, S. Pasky
Water from individual closed-loop deionized (DI) water systems is used to regulate the temperature of high-power RF components at the Advanced Photon Source (APS) S-Band linac. The RF components are made of oxygen-free high-conductivity copper and respond quickly to temperature, resulting in changes in the beam energy when the temperature is poorly regulated. Temperature regulation better than /spl plusmn/0.1/spl deg/F is required to achieve good energy stability. Improvements in the closed-loop water systems have enabled us to achieve a regulation of /spl plusmn/0.05/spl deg/F over long periods. In the long term, depletion of copper from the water circuits is a very real and serious concern, thus steps are being taken to reduce corrosion. Temperature regulation philosophy and equipment are discussed and numerical results are presented. Steps to decrease copper corrosion are also discussed.
来自单个闭环去离子水系统的水用于调节先进光子源(APS) s波段直线加速器的高功率射频元件的温度。射频组件由无氧高导电性铜制成,对温度的响应很快,当温度调节不良时,会导致光束能量的变化。温度调节优于/spl plusmn/0.1/spl度/F,以获得良好的能量稳定性。闭环水系统的改进使我们能够在长期内实现/spl plusmn/0.05/spl°/F的调节。从长远来看,水回路中铜的损耗是一个非常现实和严重的问题,因此正在采取措施减少腐蚀。讨论了温度调节原理和设备,并给出了数值结果。讨论了降低铜腐蚀的措施。
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引用次数: 3
Reduction of X-BPM systematic errors by modification of lattice in the APS storage ring 通过修改APS存储环中的晶格来减小X-BPM系统误差
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.794369
G. Decker, O. Singh, H. Friedsam, J. Jones, M. Ramanathan, D. Shu
With recent developments, X-ray beam position monitors (BPMs) are capable of making accurate photon position measurements down to the sub-micron level. The true performance of X-ray beam position monitors when installed on insertion device beamlines is, however, severely limited due to the stray radiation traveling along the beamline that contaminates the insertion device photons. The stray radiation emanates from upstream and downstream dipole magnet fringe fields, from steering correctors, and from sextupoles and quadrupoles with offset trajectories. While significant progress has been made at the APS using look-up tables derived from translation stage scans to compensate for this effect, performance of ID X-BPMs to date is at the 10 to 20 micron level. A research effort presently underway to address this issue involves the introduction of a chicane into the accelerator lattice to steer the stray radiation away from the X-ray BPM blades. A horizontal parallel translation of the insertion device allows only ID photons and radiation from two nearby correctors to travel down the beamline, simplifying the radiation pattern considerably. A detailed ray tracing analysis has shown that stray radiation gets displaced by up to 2 cm horizontally at the X-BPM locations so that it can be easily masked. Results from such a modified lattice, implemented for one of the insertion devices, are reported here.
随着最近的发展,x射线束位置监测器(bpm)能够精确测量到亚微米级的光子位置。然而,当安装在插入设备的光束线上时,由于沿光束线行进的杂散辐射会污染插入设备的光子,因此x射线光束位置监测器的真实性能受到严重限制。杂散辐射来自于上游和下游的偶极磁体边缘场、转向校正器以及偏离轨迹的六极和四极。虽然APS已经取得了重大进展,使用从平移阶段扫描派生的查找表来补偿这种影响,但迄今为止,ID x - bpm的性能仅在10到20微米的水平。为了解决这个问题,目前正在进行的一项研究工作包括在加速器晶格中引入一个弯道,以引导x射线BPM叶片的杂散辐射。插入装置的水平平行平移只允许来自两个附近校正器的ID光子和辐射沿光束线传播,大大简化了辐射模式。一项详细的射线追踪分析表明,在X-BPM位置,杂散辐射被水平偏移了2厘米,因此很容易被掩盖。本文报道了在其中一个插入器件上实现的这种改进晶格的结果。
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引用次数: 7
A periodically-switched ODE model for N-bunch beamloading in a storage ring 存储环中n束束加载的周期切换ODE模型
Pub Date : 1999-04-20 DOI: 10.1109/PAC.1999.795452
C. Schwartz, A. Nassiri
A new baseband formulation of the coupled cavity/longitudinal-bunch ODEs is derived. Assuming linearity, a model of the form x/spl dot/(t)=A(t)x(t)+B(t)u(t) arises, where A(t) and B(t) are piecewise constant, and periodic with the revolution period T/sub 0/. Such models, known in the control community as (periodic) switched systems, have known (in)stability criteria and control theoretic properties, which can be useful in the analysis and control of multiple bunch beamloading.
推导了耦合腔/纵束ode的一种新的基带公式。假设线性,一个形式为x/spl点/(t)= a (t)x(t)+B(t)u(t)的模型出现,其中a (t)和B(t)是分段常数,并且周期为t/下标0/。这种模型在控制界被称为(周期)切换系统,具有已知的(in)稳定性准则和控制理论性质,可用于多束波束加载的分析和控制。
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引用次数: 0
期刊
Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366)
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