Dynamic aperture (DA) is one of the key nonlinear properties for a storage ring. Although there have been both analytical and numerical methods to find the aperture, the reverse problem of how to optimize it is still a challenging problem. A general and flexible way of optimizing the DA is highly demanded in accelerator design and operation. In this paper, we discuss the use of multiobjective optimization for DA. First we consider using objective functions based only on numerical tracking results. Data mining of these results demonstrated a correlation between DA and low-order nonlinear driving terms. Next we considered using objective functions which included both numerical tracking results and analytical estimates of low-order nonlinear driving terms. This resulted in faster convergence. The National Synchrotron Light Source II (NSLS-II) lattice was taken as an example to illustrate this method. This multiobjective approach is not limited by particular linear or nonlinear lattice settings, and can also be applied for optimizing other properties of a storage ring.
The particle motion in storage rings is coupled between the longitudinal and the transverse planes in the presence of nonzero dispersion rf cavities. We found that the particle motion can be modeled separately with a redefined closed orbit. The closed orbit can be described by a Green's function, which was confirmed in the simulation and in the experiment. The pathlength is calculated from the redefined closed orbit, and we found that the longitudinal phase slip is related not only to the momentum, but also to the rf phase of the particle. The effect on the longitudinal motion becomes significant if the phase slip caused by the rf cavities is large or if the momentum compaction factor is small, such as in the lower alpha- lattice which is intended to produce shorter bunches.
We show that the quadrupole-mode transfer function (QTF) is a powerful nondestructive tool to measure properties of dynamical systems. In particular, we discuss the feasibility of using the QTF to measure the betatron tunes and the beam emittances with a beam-position monitor system. The QTF can also be used to compensate the optical mismatch during the beam injection process. However, it is less effective than the rf dipole method in overcoming the intrinsic spin resonances for polarized beam acceleration.
We present the conceptual design of the NSLS-I1 injection system [I, 21. The injection system consists of a lowenergy linac, booster and transport lines. We review two different injection system configurations; a booster located in the storage ring tunnel and a booster housed in a separate building. We briefly discuss main parameters and layout of the injection system components.
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