Advanced accelerator research promises to improve the power and efficiency of today's particle accelerators, enhancing applications in medicine and high-energy physics, and providing potential benefits for research in materials, biological and energy science. FACET—Facilities for Accelerator science and Experimental Test beams at SLAC—will study plasma acceleration, using short, intense pulses of electrons and positrons to create an acceleration source called a plasma wakefield accelerator.
Plasma wakefield acceleration is one of the most promising approaches to advancing accelerator technology. This approach offers a potential 1,000-fold or more increase in acceleration over a given distance, compared to existing accelerators. SLAC is the only place in the world with the high peak current, high-energy electron and positron beams required to continue the development of beam-driven plasma wakefield acceleration.
FACET will re-use components from previous SLAC experiments to develop the new accelerator technology. With FACET, the SLAC linac will support a unique program concentrating on second-generation research in plasma wakefield acceleration. FACET will meet the Department of Energy Mission Need Statement for an Advanced Plasma Acceleration Facility. Its program will achieve several key steps on the roadmap to a plasma wakefield linear collider and will sustain US leadership in accelerator physics.
FACET's unique high-power beams will provide other important science opportunities, both for high-energy physics and basic energy sciences. In addition to plasma wakefield acceleration research, FACET will support a user facility as part of its science program. User opportunities will include accelerator development for the proposed International Linear Collider, dielectric wakefield accelerators, as well as terahertz radiation and materials science research.
As high-energy physics strives to unveil the fundamental nature of universe, experimental machines require ever higher energies to "see" how matter behaved in the extreme conditions that must have existed just after the Big Bang. Providing such machines within feasible costs is a major challenge that calls for new, perhaps even radical, approaches to particle acceleration. In the past seven years, plasma wakefield accelerators have emerged as a leading approach, thanks to progress on a number of fronts. The Final Focus Test Beam facility at SLAC showed that plasmas can accelerate and focus both electron and positron high-energy beams. In addition, they have demonstrated a variety of new effects, most notably the acceleration of electrons from the plasma itself with extremely high "gradients" or acceleration per length of accelerator. Accelerating wakefields in excess of 50 GeV/m have been sustained in an 85 cm-long plasma—roughly 3,000 times the gradient in the SLAC linac. The wakefield in an approximately 1-meter-long plasma accelerated some of the 42 GeV electrons to energies approaching 100 GeV.
The new FACET project will take this work forward, extending high-gradient plasma acceleration from particles to discrete bunches and working to create beams suitable for an electron-positron collider of unprecedented energies.