Abstract
Modern synchrotron light sources are competing intensively to increase x-ray brightness and, eventually, approach the diffraction limit, which sets the final goal of lattice emittance. All recent synchrotron facility upgrades follow the multibend achromat approach by arranging small horizontal beta function and dispersion inside discrete bending dipoles. In this paper we propose a concept of a lattice element that we call ``complex bend,'' which has the potential of becoming a main building block for low emittance lattices. The complex bend is a sequence of dipole poles interleaved with strong alternate focusing so as to maintain the beta function and dispersion oscillating at low values. Comprising the ring lattice with complex bends, instead of regular dipoles, will minimize the $H$-function and reduce horizontal emittance while localizing bending to a small fraction of the storage ring circumference, which should provide more space for insertion devices. In this paper we present the details of the complex bend, considerations regarding the choice of optimal parameters, and thoughts for its practical realization. We focus here on complex bend physics and engineering design, rather than integration of this complex bend into a specific ring lattice.
Highlights
The trend of minimizing the emittance of modern synchrotrons translates into reduction of dispersion and beta functions in their lattice dipoles
In this paper we propose a concept of a lattice element that we call “complex bend,” which has the potential of becoming a main building block for low emittance lattices
The complex bend is a sequence of dipole poles interleaved with strong alternate focusing so as to maintain the beta function and dispersion oscillating at low values
Summary
Due to mechanical constraints on the overall length of a single structure, the period of a complex bend must be short (∼10 cm); this results in high gradients of the pole fields. For this particular example we have chosen K1F 1⁄4 100 m−2 and K1D 1⁄4 −80 m−2. A combination of K1 and pole length values as shown above corresponds to the focusing distance of 20 cm for the quadrupole poles inside the complex bend element. We note that aligning separate poles and making precise magnetic measurements become impractical for a long complex bend structure with many cells
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