The Sirius Heating System for the In-situ NEG Activation

Abstract

Sirius is a 3 GeV fourth-generation synchrotron light source under commissioning in Brazil, with 518 m circumference and a bare lattice emittance of 0.25 nm.rad. This ultra-low emittance machine is based on approximately 700 magnets with 28 mm typical gap. The standard vacuum chamber, that makes up around 80% of the circumference, is a 26 mm external diameter copper tube. Due to the small conductance of the chambers and the limited space between the magnets, the vacuum pumping will be based on distributed concept and then non­-evaporable getter (NEG) coating will be extensively used. To activate the NEG coating, the chambers must be heated at 200°C for about 24 hours. The solution for Sirius was the development of an ultra-thin heating tape, 0.4 mm thick, which allows an in-situ bake-out. The developed tapes are able to operate continuously at 220°C and have in their design a thermal shield that reduces the radiation heat loss to the magnets. This paper describes the development of the heating tape, its power supply, the control software and the operation of the system during the NEG activation at Sirius.