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Design of a Novel Stacked Storage Ring for Low Emittance Light Sources
[Thesis]. Manchester, UK: The University of Manchester; 2016.
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Abstract
Storage ring light sources are in use around the world operating as high brightness photon sources from the infrared to the X-ray photon regimes. Whilst modern light source designs achieve horizontal emittances in the few-nm range, they are only diffraction limited in the vertical plane with emittances as low as 10~pm-rad. To achieve fully diffraction limited light sources in the X-ray regime requires a fundamental change in the design of such machines. Many such designs have been proposed based on the multi-bend achromat (MBA) lattice, which have been shown to achieve the required emittance reduction. However MBA lattices typically have a reduced dynamic acceptance, and consequently shorter beam lifetimes. Whilst this can be ameliorated somewhat through the use of top-up injection schemes, many issues still remain. In this thesis we explore one possible alternative to the multi-bend achromat (MBA) paradigm: the stacked storage ring. We propose a storage ring consisting of two synchrotrons joined via a static magnetic vertical transfer line. One of the rings has a reduced emittance through the use of high field damping wigglers, whilst the other is used for standard user experiments. The cumulative emittance of the combined ring structure is a function of the emittances of the two rings. The stacked ring approach allows for a reduction in the beam emittance without a consequent increase in the machine footprint, as in the case of the MBA lattice. Additionally, we may use the more relaxed lattice structures popular in currently operating 3rd generation light sources to maintain a reasonable dynamic acceptance even with the reduced emittance.We apply the stacked storage ring concept to the design of a low emittance 700~MeV compact light source for low energy vacuum ultraviolet photon output. The desirability of such a low energy photon source for UK science has previously been explored in depth. We examine the design of such a light source based around a strong damping stacked storage ring in the presence of Touschek and Intra-Beam scattering whilst analysing the effects on the dynamic properties of the lattice. We also apply the stacked ring concept to two lattices designed to operate in the high energy X-ray region of the photon spectrum and investigate the potential advantages in this regime, including as an adjunct to further improve proposed MBA concepts.