Researchers have developed a new technique for accelerating electrons on plasma waves that could lead to a new generation of particle accelerators.
The news findings could not only make accelerators more economical, but expand their use in areas such as medicine, national security, and high-energy physics research, the DEO/SLAC National Accelerator Laboratory reported.
The findings demonstrate the efficiency of plasma wakefield acceleration, in which electrons gain energy by "surfing" on a wave of electrons within ionized gas. The researchers used SLAC's Facility for Advanced Accelerator Experimental Tests (FACET) to boost groups of electrons to energies up to 500 times higher that can be reached with a traditional accelerator; a feat that has never been reached before.
"Many of the practical aspects of an accelerator are determined by how quickly the particles can be accelerated," said SLAC accelerator physicist Mike Litos, lead author of the paper. "To put these results in context, we have now shown that we could use this technique to accelerate an electron beam to the same energies achieved in the 2-mile-long SLAC linear accelerator in less than 20 feet."
Researchers have been looking at plasma wakefields as a way to create smaller, cheaper accelerators for three decades. In 2007 the UCLA and SLAC groups announced they had successfully accelerated lectrons at the end of an electron bunch from 42 billion electronvolts to 85 billion electronvolts.
In this recent experiment researchers sent pairs of electron bunches containing between five and six billion electrons each into a laser-generated column of plasma. The leading bunch in each pair worked to blast free electrons away from the lithium atoms, leaving behind the positively charged lithium nuclei in what are referred to as the "blowout regime." The second bunch of electrons, known as the "trailing bunch," fell back behind the second bunch , creating a "plasma wake" that propelled the trailing bunch to higher energy.
"These results have an additional significance beyond a successful experiment," said Mark Hogan, SLAC accelerator physicist and one of the principal investigators of the experiment. "Reaching the blowout regime with a two-bunch configuration has enabled us to increase the acceleration efficiency to a maximum of 50 percent -- high enough to really show that plasma wakefield acceleration is a viable technology for future accelerators."
In order for wakefield acceleration to actually be put to use the trailing bunches must first be perfectly shaped and spaced so the electrons each receive the exact same energy boost.
"We have our work cut out for us," Hogan said. "But you don't get many chances to conduct research that you know in advance has the potential to be immensely rewarding, both scientifically and practically."
The findings were published in a recent edition of the journal Nature.