Abstract
The Advanced Light Source Upgrade will implement on axis single-train swap-out injection employing an accumulator between the booster and storage rings. The accumulator ring (AR) design is a twelve period triple-bend achromat that will be installed along the inner circumference of the storage-ring tunnel. A nonconventional injection scheme will be utilized for top-off off axis injection from the booster into the AR meant to accommodate a large $\ensuremath{\sim}300\text{ }\text{ }\mathrm{nm}$ emittance beam into a vacuum-chamber with a limiting horizontal aperture radius as small as 8 mm. The scheme incorporates three dipole kickers distributed over three sectors, with two kickers perturbing the stored beam and the third affecting both the stored and the injected beam trajectories. This paper describes this ``3DK'' injection scheme and how it fits the AR's particular requirements. We describe the design and optimization process, and how we evaluated its fitness as a solution for booster-to-accumulator ring injection.
Highlights
The Advanced Light Source-Upgrade (ALS-U) is the upgrade of the Advanced Light Source to a fourth generation diffraction-limited soft x-ray light source [1]
Achieving ALS-U’s high-brightness goal requires strong focusingmagnet gradients; the strong gradients necessitate strong chromatic sextupoles and these will shrink the dynamic aperture of the storage ring (SR) to about 0.5 mm radius once lattice imperfections are taken into account
Consideration of these demands has guided the choice of injection scheme that recognizes that the accumulator ring (AR) can tolerate a significant injection transient
Summary
The Advanced Light Source-Upgrade (ALS-U) is the upgrade of the Advanced Light Source to a fourth generation diffraction-limited soft x-ray light source [1]. Achieving ALS-U’s high-brightness goal requires strong focusingmagnet gradients; the strong gradients necessitate strong chromatic sextupoles and these will shrink the dynamic aperture of the storage ring (SR) to about 0.5 mm radius once lattice imperfections are taken into account. The AR design has to fulfill two competing demands on the vacuum-chamber aperture: it should be wide enough to accept the large emittance beam from the booster, with a goal of ≳95% injection efficiency, but as narrow as possible to minimize the magnets’ aperture and their weight and volume so that the AR can fit in the same tunnel as the SR Consideration of these demands has guided the choice of injection scheme that recognizes that the AR can tolerate a significant injection transient. Alternatives to the 3DK injection scheme are discussed in the Appendix
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