Pulsed sextupole injection for Sweden’s new light source MAX IV

Abstract

The MAX IV facility presently under construction will include two storage rings for the production of synchrotron radiation. Both rings will be operated at a constant 500 mA of stored current with top-up shots supplied by the MAX IV linac acting as a full-energy injector. Until recently, injection into both storage rings was designed using a conventional approach: a closed four-kicker injection bump brings the stored beam to the septum blade where the injected bunches are captured in a single turn. This method, although commonly found in third generation light sources, has significant disadvantages. Therefore, an alternative injection into the storage rings using pulsed multipoles has been investigated. This type of injection does not require an injection bump and has the potential to make top-up injection fully transparent to users. Design studies have been successfully completed and as a consequence it has been decided to replace the originally foreseen conventional injection scheme with pulsed multipole injection in both MAX IV storage rings. This paper reports on these studies, presents pulsed sextupole injection schemes, and summarizes requirements for the pulsers, sextupole magnets, and vacuum chambers.

Longitudinal injection scheme using short pulse kicker for small aperture electron storage rings

“…These values are taken from Ref. [13]. The bunch described above is injected with a time offset of −5 ns with respect to a circulating bunch, which corresponds to exactly the point equidistant to two successive circulating bunches, and a relative energy offset of þ4.3%.…”

The MAX IV storage ring project

“…At BESSY II this kicker delivers roughly 1 mrad of kick at 12 mm distance from the stored beam. The separation of the injected bunch from the stored beam in MAX IV is, however, only about 5 mm (Leemann, 2012b). In order to apply the BESSY kicker design to MAX IV the vertical separation of the inner rods would have to be reduced to levels that are no longer compatible with the vertical acceptance requirements.…”

“…Top: trajectory of the injected bunches in the MAX IV 3 GeV storage ring starting at the septum (Leemann, 2012b). The PSM is installed in the second long straight and kicks the injected bunch into the ring acceptance.…”

“…The strong non-linearity of betatron motion in the 3 GeV storage ring, however, required optimization of the pulsed multipole injection (PMI) scheme with tracking studies in order to determine the best location and kick amplitude for the pulsed multipole (Leemann, 2012b). A scheme was developed for a pulsed sextupole magnet (PSM) using both single-turn and two-turn injection as well as different kick strengths (cf.…”

“…The 1.5 GeV ring (MAX IV, 2010;Leemann, 2012c) will replace the existing MAX II (Andersson et al, 1994) and MAX III (Sjö strö m et al, 2009) rings in delivering UV, soft X-ray and infrared radiation. With about the same circumference (96 m) as MAX II, the 1.5 GeV ring will deliver a smaller emittance (6 nm rad) than its predecessor by applying the same compact multipurpose magnet design concept (Johansson, 2011) as in the 3 GeV ring to a 12-fold DBA lattice.…”