Abstract
In recent years nonuniform dipoles with bending-radius variation have been studied for reducing storage ring emittance. According to a new minimum-emittance theory, the effects of an arbitrary dipole can be characterized with two parameters determined by the dipole. To have a better idea of the potentials of nonuniform dipoles, here we numerically explore the possible values of these two parameters and associated bending profiles for optimal emittance reduction. Such optimization results provide a useful reference for lattice designs involving nonuniform bending. Simple bending-radius profiles (a short segment of constant radius with linear ramps on the sides) were found to be close to the optimal. Basic beam and lattice properties such as emittance, energy spread, and phase advances are presented based on the optimal dipole solutions.
Highlights
Minimizing beam emittance in storage rings is desired due to ever-increasing demands for higher beam quality for both modern synchrotron light sources and damping rings in high-energy linear colliders
Three commonly interested lattice types have been studied: (1) lattices with achromatic arcs, which are useful in providing dispersion-free straight sections for light sources, rf cavities, injection/ejection, and so on; (2) lattices without any constraints except for minimizing the natural betatron emittance, which is the figure of merit for damping rings of linear colliders; and (3) lattices without any constraints but minimizing the effective emittance at the straight sections, which is often the figure of merit for light sources because it takes into account the effects of
Using genetic-algorithm-based multiobjective as well as single-objective optimizations of arbitrary bending profiles without field reversion, we established the optimal profiles for emittance minimization and the corresponding theoretical minimum emittances for AME, TME, and EME lattices
Summary
Minimizing beam emittance in storage rings is desired due to ever-increasing demands for higher beam quality for both modern synchrotron light sources and damping rings in high-energy linear colliders. There have been efforts to reduce the emittance below the well-known theoretical minimum by using dipoles with bending-radius variation [1,2,3,4,5].
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