The Vacuum System of the Low Energy Ion Ring at CERN: Requirements, Design, and Challenges

For the heavy ion program at CERN’s Large Hadron Collider, lead-lead collisions with a design luminosity of 10**27 cm**-2s**-1 are foreseen. This will be achieved after an upgrade of the ion injector chain where the Low Energy Antiproton Ring (LEAR) is currently converted into a Low Energy Ion Ring (LEIR). Avalanche-like heavy-ion induced molecular desorption, first observed at LEAR and systematically studied at CERN’s Heavy Ion Accelerator (LINAC 3), is the major challenge to achieve the required average dynamic pressure of about 4 x 10**-12 mbar in LEIR. The LEIR vacuum requirements, the technical design, the implementation of non-evaporable getter coatings and low-outgassing collimators, and the concept of ion-beam scrubbing are reviewed in this paper.