History and Context of JLab SRF

When the Continuous Electron Beam Accelerator Facility (CEBAF) project began in the mid-1980s at what came to be called the Thomas Jefferson National Accelerator Facility (Jefferson Lab), there was an immediate need to gear up to meet challenges for implementing the then-novel SRF technology on which CEBAF was to be based. CEBAF’s 7/8-mile, racetrack-shaped underground accelerator tunnel was to contain in each “straightaway” a microwave superconducting linac operating at 2 K. This represented an order-of-magnitude increase in the scale of SRF accelerators.

SRF is a complex multidisciplinary field that is still advancing. Not all of its limits or applications are yet known, and it has not reached a technological plateau. SRF includes solid-state physics, surface science, low-temperature physics, electromagnetism, materials science, rf and microwave technologies, feedback and control systems, interactions between radio waves and the beams they accelerate, vacuum science, mechanical engineering, and cryogenics. In the mid-1980s, when the CEBAF project began applying SRF at an industrial scale for the first time anywhere in the world, the challenges were technological, industrial, and in some cases scientific. SRF was a newly developed technology, and reliable SRF components needed to be manufactured, processed, assembled, tested, and installed on a production basis. In some cases, subcomponents had to be researched and developed.

As a result, Jefferson Lab’s SRF R&D capabilities were born, together with limited, purpose-built production capabilities targeted on the task of building CEBAF. These SRF capabilities were based in large part on the importation of a contingent of people from the successful SRF R&D program at Cornell University and Stanford. A pre-existing high-bay facility on CEBAF’s site, which had been inherited from NASA, was converted largely to SRF purposes. The CEBAF project went forward, and a s of 2004, CEBAF has been reliably serving nuclear and particle physics experimental users with SRF-accelerated beams of electrons having outstanding characteristics for nearly a decade. Because CEBAF’s scientific successes have led directly to a new generation of questions about the quark structure of nuclei, and because CEBAF itself has performed so well, an upgrade that will double CEBAF’s energy is a near-term component of the Office of Science’s road map, Facilities for the Future of Science: A Twenty Year Outlook

However, it is not only CEBAF that underlies the growing international recognition of Jefferson Lab’s strengths in SRF science and technology. Working in partnership with other national labs, Jefferson Lab has also contributed design and engineering of the SRF linac and the associated cryogenics system at the heart of the Spallation Neutron Source (SNS), currently the largest SC project. Moreover, Jefferson Lab’s IR Demo Free-Electron Laser (FEL)—the world’s highest-average-power source of tunable coherent IR light—was based on CEBAF’s SRF technology, as is the FEL upgrade now being commissioned. Jefferson Lab’s SRF expertise, experience, and facilities combine to position the laboratory to contribute usefully to a host of future accelerator and accelerator-based projects.