- Number 304 |
- February 1, 2010
Berkeley Lab’s Wim Leemans and his incredible shrinking accelerators
Wim Leemans of DOE’s Lawrence Berkeley National Laboratory’s is among the pioneers of laser wakefield acceleration, with its promise of accelerating gradients up to 10,000 times greater than today’s conventional accelerators. Leemans and his group not only achieved one of the technology’s earliest practical demonstrations but used a technique that has since led to still-diminutive but dramatically more powerful accelerators.
Last December DOE recognized Leemans’ contributions with one of six Ernest Orlando Lawrence Awards, the Department’s highest honor. Lawrence’s cyclotron was the ancestor of the modern particle accelerator, and Leemans is particularly suited to carry on his tradition.
A native of Belgium, Leemans earned bachelor’s degrees from the Free University of Brussels and advanced degrees, including his 1991 Ph.D. in electrical engineering, from the University of California at Los Angeles. At UCLA he was inspired by the vision of John Dawson and Toshiki Tajima, who had first proposed plasma acceleration in 1979.
Leemans joined Berkeley Lab in 1991 and soon formed the Laser Optical Systems Integrated Studies (LOASIS) group. At the time, lasers powerful enough to actually accelerate electrons in a plasma had a tendency to blow themselves up. By applying Mourou and Strickland’s new chirped-pulse method for safely amplifying laser power, the LOASIS team, along with two other groups, achieved high-quality electron beams with laser wakefield accelerators in 2004. Instead of brute force, however, the LOASIS group applied their original concept of plasma-channel guides, analogous to optical fibers, to reach beam energies of 80 million electron volts (80 MeV), a feat that was prominently displayed on the cover of Nature.
Plasma channels proved the key to higher energies. In 2006 LOASIS researchers garnered worldwide attention by using a plasma channel in a block of sapphire to accelerate high-quality electron beams to a billion electron volts (1 GeV) in a distance of just 3.3 centimeters.
With DOE support, Leemans and LOASIS, now a full-fledged program in the Accelerator and Fusion Research Division, recently initiated the petawatt Berkeley Lab Laser Accelerator, BELLA, whose aim is 10 GeV in less than a meter. Primarily a research facility for investigating advanced accelerator concepts, the BELLA laser accelerator may also form the core of a user facility unlike any in the world for research in physics, chemistry, biology, and materials.
By colliding a 10-GeV electron beam with a separate petawatt laser pulse, for example, extraordinarily high electric fields may be created in which accelerated electrons could gain enough energy to create electron-positron pairs out of the vacuum. Known as “snapping” or “boiling” the vacuum, it’s a regime more familiar to astrophysicists who study the interiors of supernovae than laser scientists.And all on a tabletop! Well, maybe just a little bit bigger, including the lasers....
Submitted by DOE's Lawrence Berkeley National Laboratory