Vacuum System

The vacuum system defines the environment in which the electron beam travels under the influence of electromagnetic fields. This environment should be substantially free of gas molecules, since collisions between the electron beam and gas molecules can lead to loss of stored electrons and a rapid decrease in the beam current.

The average pressure over more than 500 meters long vacuum environment of the Sirius storage ring must be a trillion times lower than the atmospheric pressure. This corresponds to what is called ultra-high vacuum and requires several special techniques for its production.

The vacuum environment is physically delimited by a vacuum chamber. In the Sirius storage ring, the vacuum chamber in the region of the quadrupoles and sextupoles will be cylindrical, with a radius of 12 mm for the free region for the electrons, considerably lower than the values normally used in the current synchrotron light sources. As a comparison, the radius of the vacuum chamber of the UVX storage ring is 30 mm.

The small size of the vacuum chamber brings several consequences, among which is the need for distributed pumping with the use of the NEG (Non-Evaporable Getters) technology. The NEG is a thin film deposited on the inner surface of the vacuum chamber capable of trapping gases, providing a vacuum pumping effect. The technology for deposition of these films was established and tested at LNLS, after agreement with CERN (European Organisation for Nuclear Research).