12 GeV Upgrade Technical Scope - Accelerator

The accelerator portion of the upgrade will be constructed on the framework of the existing CEBAF accelerator. A 12 GeV beam to Hall D and up to an 11 GeV beam is needed for Halls A, B, and C. To achieve this, the accelerator will be upgraded to 2.2 GeV/pass (1.1 GeV/linac) and the beam transport system upgraded and expanded. These upgrades will be made:

  • Ten new higher-voltage cryomodules, i.e., superconducting radio-frequency (SRF) accelerating elements (five per Linac).
  • Ten new RF stations to power the 10 new cryomodules.
  • Approximately double the refrigeration capacity.
  • Modifications to the magnets in the recirculation arcs and their power supplies to keep the higher energy beam confined to the existing beam path.
  • Modifications to the extraction system to support the higher energy beams.
  • A tenth arc-beamline to provide an extra pass through the North Linac. This additional acceleration pass will bring the beam up to the 12 GeV required to accommodate the experimental program in the new hall (Hall D).
  • A new beamline connecting Hall D to the baseline accelerator.

The beam transport system will carry 12 GeV beam to Hall D as well as beam at energies up to 11 GeV to Halls A, B, and C. The choreography required to accomplish these tasks is complicated and will require increasing the strength of the bending and focusing magnets. Modifications to the system of magnets, which separates the beams into their proper paths through the recirculation arcs and them recombines them for the pass through the acceleration sections, also will be completed.