SR Power Distribution along Wiggler Section of ILC DR
SR Power Distribution along Wiggler Section of ILC DR
复制标题
沿 ILC DR Wiggler 部分的 SR 功率分布
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
K. Zolotarev
中科院分区：
文献类型：
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作者：
O. Malyshev;M. Korostelev;N. Collomb;S. Postlethwaite;John M. Lucas;A. Wolski;K. Zolotarev
为了提供短的辐射阻尼时间，每个ILC阻尼环都需要一个长摆动器。由摆动器中的光束产生的同步辐射（SR）必须被真空容器的不同组件吸收，包括专门设计的吸收器。机械设计、真空系统和电子云缓解的优化需要精确计算SR功率分布。基于最新的点阵设计[1]，计算了单个摆动器的角功率分布（使用内部开发的软件）。然后，将所有摆动器的SR叠加在一起，就可以计算沿摆动器段和下游直线段的所有部件的功率分布。DCO4晶格设计[1]中的ILC正电子阻尼环（DR）包含一个374米长的摆动器部分，由88个连续的摆动器模块组成。本部分的设计是由许多不同的要求驱动的，包括光束动力学、孔径、电子云减缓、真空规格、SR功率吸收和成本[2]。名义上，电子阻尼环使用相同长度的摆动器，尽管这可以减少，因为来自电子源的光束比来自正电子源的光束小，因此需要更少的阻尼。电子云减缓的要求之一是，在摆动器和四极体内部的真空室上的光子通量必须保持在最低限度。每个模块所需的bpm也应与SR隔开，以减少背景噪音。这意味着在每个摆动器模块的出口处需要一个集总SR吸收器。功率吸收系统的设计具有挑战性，因为来自摆动器的SR功率以窄角度发射，并且功率密度达到足以破坏真空室材料的值。为了优化工程解决方案，必须计算真空室不同部位的SR功率密度分布。通常，在设计最终完成之前，机械设计和SR功率密度分布的计算之间需要进行一些迭代。本文报告了ILC DR摆动器截面设计优化的主要步骤和结果。SR功率分布的计算通过对功率密度谱[3]:2 2 21 （),16 T x z dP dP P f f d d d K K K(1)，其中）（）（）（）（）（）（）（633），可以估计SR功率密度的角分布。0) (2 2 A I m L T B GeV E kW P w T为摆振器发射的SR全功率，E为光束能量，Bw为摆振器中的峰值场，L为摆振器长度，I为光束电流。函数fx和fz描述了功率密度的水平和垂直分布，可以写成：
A long wiggler section is required in each ILC damping ring to provide short radiation damping times. Synchrotron radiation (SR) generated by the beam in the wigglers must be absorbed by different components of the vacuum vessel, including specially designed absorbers. The optimisation of the mechanical design, vacuum system and electron cloud mitigation requires accurate calculation of the SR power distribution. The angular power distribution from a single wiggler was calculated (with software developed in-house) based on the latest lattice design [1]. Then the superposition of SR from all wigglers allows calculation of the power distribution for all components along the wiggler section and the downstream straight section. INTRODUCTION The ILC positron damping ring (DR) in the DCO4 lattice design [1] contains a 374 m long wiggler section, consisting of 88 consecutive wiggler modules. The design of this section is driven by a number of different requirements, including beam dynamics, aperture, electron cloud mitigation, vacuum specification, SR power absorption and cost [2]. Nominally, the electron damping ring uses the same length of wiggler, although this could be reduced, because the beam from the electron source is smaller than that from the positron source, and therefore requires less damping. One of the requirements from electron cloud mitigation is that the photon flux on the vacuum chamber inside wigglers and quadrupoles must be kept to a minimum. The BPMs required in each module should also be screened from SR to reduce background noise. This means that a lumped SR absorber is required at the exit of each wiggler module. Design of the system for power absorption is made challenging by the fact that the SR power from the wiggler is emitted in a narrow angle, and the power density reaches values sufficient to destroy the material of the vacuum chamber. To optimise the engineering solution, the SR power density distribution on different parts of the vacuum chamber must be calculated. Generally, some iteration is required between the mechanical design and the calculation of the SR power density distribution, before the design is finalised. In this paper, we report the main steps and results of the design optimization procedure for the ILC DR wiggler section. CALCULATION OF SR POWER DISTRIBUTION The angular distribution of SR power density can be estimated with a formula obtained by integrating the power density spectrum [3]: 2 2 21 ( ), 16 T x z dP d P P f f d d d K K (1) Where ) ( ) ( ) ( ) ( 633 . 0 ) ( 2 2 A I m L T B GeV E kW P w T is the full power of SR emitted by a wiggler, E is the beam energy, Bw is the peak field in the wiggler, L is the wiggler length and I is the beam current. The functions fx and fz describe the horizontal and vertical distribution of the power density and can be written as: