The most powerful particle accelerators on Earth are research machines built on superconducting radiofrequency (SRF) technology. This technology uses superconductors to improve the precision of radio frequency devices. These unique research machines are expensive and difficult to operate. They also require huge support systems and teams to run. Scientists have now built an accelerator prototype that uses off-the-shelf support systems. The prototype shows it is possible to build and run powerful non-research accelerators at a fraction of the cost of research
Powerful particle accelerators have a wide range of uses in medicine and industry. For example, particle beams could be used for wastewater treatment or to produce isotopes for nuclear medicine. However, widespread use of accelerators is limited by their cost, size, and dependence on complex support systems. Scientists are overcoming these limitations with new advances in accelerator technology. These advances include new approaches to SRF design. Scientists have used these advances to build an accelerator prototype that is less expensive, small, and runs with off-the-shelf support systems. This would enable more industrial and medical use of particle accelerators.
To develop the prototype accelerator system, the researchers applied advances in accelerator component technology, materials science, and self-contained refrigeration. First, they replaced the SRF accelerator cavities—the components at the heart of an accelerator. SRF cavities are typically made of pure niobium and function well when cooled to within a few degrees of absolute zero. The new design uses niobium cavities that are coated on the inside with a compound metal of niobium and tin, enabling the cavities to accelerate particles at higher temperatures. On the outside, the cavities are coated with pure copper, which makes them easier to cool. The changes to the SRF cavities allow then be cooled for operation with an off-the-shelf cryocooler system that is commonly used for superconducting magnets in medical magnetic resonance imaging machines. This provided compact, reliable, and easy-to-use refrigeration and eliminated the need for the large-scale refrigeration plant necessary for research accelerators.
In tests, the system achieved results similar to those of a standard niobium SRF cavity, with a peak surface magnetic field of 29 millitesla, corresponding to an accelerating gradient of 6.5 megavolts/meter. The system was operated at 5 watts of dissipated power without any thermal instability.
Funding for this research was provided primarily by the Department of Energy Office of Science, including funding for the contract under which Jefferson Science Associates, LLC, operates Thomas Jefferson National Accelerator Facility. Funding was also provided by the DOE Office of Science Early Career Research Program and the Accelerator Stewardship Program within the DOE Office of Science. Assistance was also provided by General Atomics.
Ciovati, G., Cheng, G., Pudasaini, U., and Rimmer, R.A., Multi-metallic conduction cooled superconducting radiofrequency cavity with high thermal stability. Superconductor Science and Technology 33, 7 (2020). [DOI: 10.1088/1361-6668/ab8d98]
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