Design and simulation of beam injection scheme for diffraction limited storage ring
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摘要: 衍射极限储存环(DLSR)作为第四代同步辐射光源,正得到世界各国的大力发展和建设。如何在尽量减小对存储束流扰动情况下,高效率地将束流注入到储存环中,是衍射极限储存环设计与运行中的重要课题之一。传统的局部凸轨注入法有着很长的历史,应用广泛且技术成熟,但是传统凸轨注入法会对存储束流造成扰动,且衍射极限储存环的动力学孔径较小,这给传统凸轨注入法的应用带来了困难。为了解决这些问题,改进了一些传统的离轴注入法,提出并发展了一些在轴的注入方法。合肥先进光源(HALF)是规划建设中的衍射极限储存环光源,基于HALF储存环的物理设计方案,设计并应用了几种离轴或在轴的注入方案,通过粒子跟踪和模拟的方法验证了它们的可行性并研究了注入效率等物理问题,并对模拟结果进行了讨论和总结。Abstract: As the fourth synchrotron radiation light source, diffraction-limited storage rings (DLSRs) are being vigorously developed and constructed around the world. How to efficiently inject beam into the storage ring while minimizing the disturbance to the stored beam is one of the important issues in the design and operation of DLSRs. The conventional bump injection which has a long history is widely used and has mature technology. However, it disturbs the stored beam and the small dynamic aperture of DLSRs, which makes it difficult to apply the conventional bump injection on DLSRs. To solve these problems, some conventional off-axis injection method have been improved and several on-axis injection methods have been proposed and developed. Hefei Advanced Light Facility (HALF) is a DLSR under planning and construction. Based on the physical design of the HALF storage ring, a couple of off-axis or on-axis injection schemes have been designed and applied. Their feasibility has been verified through particle tracking and simulation, and physical issues such as injection efficiency have been studied. Discussion of results and conclusion are also presented.
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表 1 HALF储存环主要设计参数
Table 1. Main parameters of the HALF storage ring
circumference/
mbeam
energy/
GeVfocusing
typenatural
emittance/
(pm·rad)transverse
tunes
(H/V)natural
chromaticities
(H/V)momentum
compaction
factorenergy
loss per
turn/keVharmonic
numberRF
frequency/
MHzRF
voltage/
kVdamping
time
(H/V/L)/msnatural
energy
spread479.86 2.2 20×6BA 86.3 48.15/17.15 −77/−57 9.0×10−5 186.7 800 500 1000 27.2/37.7/23.4 0.62×10−3 表 2 脉冲多极铁注入方案主要参数
Table 2. Main parameters of pulsed multipole injection scheme
horizontal position
of the injection beam
at septum/mmincidence angle of
the injection beam
at septum/mradposition
of
septumposition of
nonlinear
kickerlength of
nonlinear
kicker/cmkick angle of
nonlinear
kicker/mrad12 −3.1 midpoint of long
straight sectiondownstream of long
straight section40 3 表 3 纵向注入方案主要参数
Table 3. Main parameters of longitudinal injection scheme
injection beam time offset/ns injection beam energy offset/% RF frequency/MHz RF voltage/kV harmonic number bunch spacing/ns −5 4.34 100 350 160 10 -
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