Jefferson Lab Upgrade OK'd

Less than a week after the largest particle accelerator in the world launched its first beams near Geneva, Switzerland, the US Department of Energy has approved construction of a $310 million project at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Newport News that it said will provide physicists with an unprecedented ability to study the basic building blocks of the visible universe.

The project will see Jefferson Lab double the energy of its accelerated electron beam from 6 billion electron volts (GeV) to 12 GeV; construct a new experimental hall; and upgrade the equipment in its three existing experimental halls. Construction funds are requested in the president's fiscal year 2009 budget request, and project completion is planned for 2015. Upgrading the 12 GeV Continuous Electron Beam Accelerator Facility (CEBAF) has been a high priority for its Office of Science, the DoE said, since it published a long-range facilities plan in 2003.

An aerial view of the Jefferson Lab's accelerator in Newport News, Va. (Photo: Shannan Kyte)

To explore protons and neutrons, the CEBAF accelerator propels a beam of electrons at nearly the speed of light around an oval-shaped "racetrack" almost a mile long and buried 25 feet underground. When the beam smashes into the experimental targets, huge detectors collect the fragments. By studying the speed, direction and energy of the scattered fragments, scientists can unveil the inner secrets of protons and neutrons.

"The 12 GeV CEBAF upgrade will enable scientists to seek answers to some of nature's most perplexing questions, expand our knowledge of the universe and benefit people around the world. The project also clearly demonstrates our nation's commitment to remaining in the forefront of scientific exploration and discovery," said Dr. Jehanne Simon-Gillo, acting associate director of DoE’s Office of Science for Nuclear Physics.

Jefferson Lab is a nuclear physics research lab devoted to the study of the building blocks of matter -- quarks and gluons -- that make up 99 percent of the mass of our everyday world. Scientists from across the US and around the world use the lab’s facilities to probe the nucleus of the atom.

Last week a new theoretical model proposed by Jefferson Lab Chief Scientist Tony Thomas and University of South Carolina professor Fred Myhrer that more than half of the spin of a proton is the result of the movement of quarks was published in Physical Review Letters.

“Rather than the way the quarks are spinning, it's the way they're moving in orbital motion. In fact, more than half of the spin of the proton is orbital motion of the quarks. That's a really fascinating thing,” Thomas said.

The CEBAF upgrade will employ new methods for studying the basic properties of the building blocks of the universe, how they are formed, how they interact and the forces that regulate these interactions.

"This is a very exciting day for all of us at Jefferson Lab; the upgrade will provide a qualitative change with an enormous enhancement to our experimental program enabling higher precision and better resolution," said Jefferson Lab Director Hugh Montgomery. "Many people have worked very hard to get us to this point, the veritable springboard. We look forward to building this wonderful machine and using its world-leading capabilities to learn more about our world."

Through experiments, physicists will use the upgraded accelerator to expand the knowledge of nuclear and particle physics. The upgrade will affect four main areas of study:

Quark Confinement — With the upgrade, physicists plan to address one of the great mysteries of modern physics -- why quarks only exist together, and never alone.
The Fundamental Structure of Protons and Neutrons — The changes will enable scientists to map in detail the distributions of quarks in space and momentum, culminating in tomography measurements that will constitute a 3-D picture of the internal structures of protons and neutrons.
The Physics of Nuclei — The improvements will allow researchers to illuminate the role of quarks in the structure and properties of atomic nuclei, and how these quarks interact with a dense nuclear medium.
Tests of the Standard Model — An upgraded facility will allow physicists to study the limits of the Standard Model, a theory that describes the fundamental particles and their interactions.

For more information, visit: www.jlab.org