In 2009 the CERN Management adopted a new organizational structure.

The scientific and engineering activities already existing in the accelerator and technical departments were regrouped to form the Accelerators and Technology Sector (ATS).

The AT Sector comprised three departments

• Beams department (BE),
• Engineering department (EN),
• Technology department (TE).

This sector was responsible for the operation and exploitation of the whole accelerator complex, with particular emphasis on the LHC, and for the development of new projects and technologies.

This structure was retained by the new CERN Management in 2016.

In 2021 the Accelerator System Department (SY) was created in the AT Sector.