Fermi National Accelerator Laboratory has been known for innovations in the design and construction of particle accelerators. For more than twenty years now, the Tevatron at Fermilab, the world's most powerful particle accelerator, has opened a doorway to exploring the deepest mysteries of the universe. The Chicago-area lab is now learning the ropes of a new accelerator technology considered crucial to the future of particle physics: the superconducting radio-frequency cavities. The laboratory is stepping up efforts to develop and test superconducting radio-frequency cavities, a key technology for the next generation of particle accelerators and the future of particle physics.
SRF cavities enable accelerators to increase particle beam energy levels while minimizing the use of electrical power by all but eliminating electrical resistance. Future experiments into the origins of the universe and nature of matter, including the proposed ILC and Project X, both of which Fermilab would like to host, will require advanced SRF technology.
SRF technology is a highly efficient way to accelerate beams of particles. It starts with shiny, curvy, virtually perfect cells made of niobium, a superconducting metal, and strung together like hollow pearls. The cells are polished in all possible ways with not a speck of dust or the slightest difference in shape. Several strings, or cavities are nestle in a vessel called a cryomodule, which bathes them in liquid helium and keeps them at the ultracold temperature that is key to their operation and efficiency.
Running through the string of pearls, or cells, is an electric field that oscillates between positive and negative at a rate of 1.3 billion cycles per second. Each cycle, or wave, swells to its peak and sinks to its valley within the space of a single cell; it is as if each cell rapidly switches between a positive and negative charge. The cycles are timed to kick charged particles riding the wave from cell to cell. Each time a positively charged proton enters a cell, that cell’s charge changes to negative, which attracts the proton. As the proton leaves the cell, the cell’s charge changes to positive and pushes the proton forward. Traversing the next cell, the proton is propelled in the same fashion. This process continues until the particle has shot all the way through the accelerator. To ensure that the gradient is as high as possible so that the particles get the high energy needed for the planned collisions, the cavities are welded, polished, high-pressurerinsed and tested to the best performance.
Scientists plan to use the SRF technology for parts of the Project X accelerator. The design of the SRF cavities for Project X would be similar to the SRF design used in a test accelerator at Fermilab and the one proposed for the International Linear Collider, a proposed electron-positron collider.