Front Ends, Vacuum

Overview

Vacuum system:

Beam stability and beam lifetime are the major requirements for good operation of the synchrotron light sources. Pressures in the range of low 10-9 mbar are typical values to be achieved during operation in order to have a good beam lifetime; the pressure inside the vacuum chamber is produced by the thermal desorption and the photon stimulated desorption processes, the interaction between the electron beam with the residual gases leads to an elastic and inelastic scattering causing electron losses and reducing the lifetime of the beam.
The main role of the vacuum system is to maintain vacuum chamber, in which the beam circulates, under very low gas pressure (called Ultra-High Vacuum (UHV)) to ensure beam stability and long lifetime. The vacuum system includes the vacuum chamber, vacuum pumps (that maintain the vacuum chamber under low gas pressure), vacuum gauges that monitor the pressure value in the vacuum chamber, in addition to the auxiliary tools and equipment. Hence to achieve the required values of the gas pressure, the following are needed:

  • A well designed vacuum chambers
  • Efficient pumping system,
  • Monitoring the pressure along the ring, 
  • Good choice of vacuum chamber materials 
  • Efficient cleaning and conditioning for the vacuum chamber. 

Front ends

A Front End (FE) is connected to the storage ring and passes through the shield wall where synchrotron light is delivered to the beamline.

The main functions of a front end are:

  1. To define the size of synchrotron light beam or photon beam (that is generated in the storage ring) delivered to the beamline.
  2. To monitor the position of the photon beam.
  3. To protect the storage ring if there is a vacuum leak in the beamline.
  4. To mitigate as much as possible, the heat load delivered by the synchrotron light to the optical components in the beamline.
  5. To allow safe access into the optical hutch when required while the machine in in operation.