More Big Bang for the buck: Argonne physicists demonstrate wakefield accelerator technology

Supplying more Big Bang for the buck may be possible with an Argonne-demonstrated particle accelerator technology. This "wakefield" technology could mean particle colliders with higher efficiencies, lower operation costs and greater collision energies to allow physicists to explore the forces and particles inside the components of the atomic nucleus by reproducing the very fires of creation in the laboratory.

Economic and technical barriers hinder scaling up current technology for next-generation linear accelerators.

Physicists borrowed the wakefield concept from nature. Just as an ocean wave accelerates a surfboard, wakefields rely on the wake created by a high-current electron beam to accelerate trailing electron bunches.

The Argonne Wakefield Accelerator (AWA) uses the electromagnetic field generated by a beam of low-energy, high-current electrons to accelerate another beam of electrons to high energy. This allows scientists to increase the energy boost per unit length to minimize costs. The AWA technology may increase energy per unit length by 200 to 300 percent.

Argonne researchers developed the mechanism for transferring energy from the high-current electron source that generates the wakefield — known as the "drive beam" — to the so-called "witness beam," which is accelerated. It is a transformer, similar in principle to the way an electric transformer steps up high-current, low-voltage electricity to low-current, high voltage.

The low-energy, high-current electron bunches generate radio frequency energy as they pass through an electrically insulating tube. As the energy is fed into another dielectric tube, the fields are increased in magnitude and the energy accelerates the second beam to higher energies.

Argonne researchers measured the energy gain of the second beam, demonstrating the wakefield theory. "The acceleration was a modest 10 million electron volts (MeV) per meter, but a new laser is expected to boost that to a sustained 100 MeV per meter and up to 500 MeV over small distances," explained Wei Gai, AWA group leader.

The 100 MeV-per-meter goal will be about 20 percent more than the Stanford Linear Accelerator’s proposed state-of-the-art accelerating structures. Researchers want to design a machine to accelerate particles to 1 billion electron volts over 10 meters — aboutthe length of an average living room.

OF TUBES AND TECHNOLOGY
The Argonne-developed advanced-ceramic dielectric tubes were crucial to the demonstration because they do not emit electrons that could break down the beam as current accelerating structures could.

Physicists also developed instrumentation for measuring witness beam acceleration and pioneered the adaptation of laser technology for use in high-current electron sources. They continue to develop design improvements to increase performance and to improve their under-standing of the physics of wakefields.

The U.S. Department of Energy’s High Energy Physics Office of Advanced Technologies is funding this research.

For more information please contact Evelyn Brown