Harmonic sextupoles for the Advanced Light Source low emittance upgrade

Abstract

The Advanced Light Source is a 3rd generation light source in operation since 1993. This light source is providing state of the art performance to more than 40 beamlines and their users thanks to the upgrades that have been completed over the last few years. Higher photon beam brightness is expected to become available to users in the near future through a new upgrade with the introduction of 48 sextupoles in the ALS lattice. Introducing new combined function magnets in an existing storage ring is a challenge due to the limited space available and a balance had to be found between magnet performance and spatial constraints. Moreover, the existing steering magnets will be replaced by the harmonic sextupoles. Therefore predicting the hysteresis behavior of the harmonic sextupole steering functions became critical for those included in the fast-orbit feedback loop (22 of them). After a brief introduction to the motivation for the upgrade and the scope of the project, we develop in this paper the different constraints driving the three required combined function magnet designs as well as their expected performance.

Optimization of harmonic sextupoles in Indus-2 electron storage ring

“…The familiar scheme to enhance the dynamic aperture is to introduce the extra families of sextupole magnets into the dispersion free straight section of the lattice, i.e. "harmonic sextupoles" [1][2][3][4][5][6][7].…”

Magnetic Design of the Advanced Light Source Harmonic Sextupoles

“…This leads to the replacement of 46 magnets and the addition of 2 sextupole in the injection sextion to make the sextupole lattice symmetric. All these constraints and the design choices we made for these magnets are developed in [5]. The constraint analysis work then resulted in 4 different magnet designs that will allow the ALS to meet its objective of increasing the photon beam brightness.…”