MAX IV 3 GeV storage ring vacuum system: from development to operation

概要

Max IV laboratory is a synchrotron light facility situated in Lund, Sweden. It houses two electron storage rings of 1.5 GeV and 3 GeV, a full-energy linear accelerator serving as an injector to the rings and to a short pulse facility.
The 3 GeV accelerator is an ultra-low emittance ring (0.33 nm rad horizontal bare lattice emittance) of 528 m in circumference. It features a seven-bend achromat lattice with 25 mm magnet aperture. Due to compact magnet design the vacuum system has very limited conductance without space for many lumped absorbers and pumps. To provide necessary pumping and to reduce PSD (Photon Stimulated Desorption) yield all the vacuum chambers were NEG (Non-Evaporable Getter) coated along the electron beam path. Furthermore, the copper vacuum pipes act as distributed absorbers to cope with heat from bending magnet radiation and some insertion devices.
The commissioning of the 3 GeV ring started in August 2015, since that time two in-vacuum undulators, one in-vacuum wiggler and one EPU (Elliptically Polarized Undulator) were installed and more will follow. Until August 2016 the accumulated beam dose in the machine was 112 Ah. The dynamic pressure rise per machine current (P/I) decreased by more than 2 orders of magnitude since the start of the operation. The product of total beam lifetime and current in multibunch mode was reaching maximum of 6 Ah.
This presentation will cover a few aspects of the design, development and installation of the 3 GeV ring vacuum system as well as most recent commissioning results.