Researchers from Lawrence Berkeley Lab (Berkeley Lab) were able to tweak a compact laser-plasma accelerator to get the particles move to a 1000 times greater energy gradient than any other traditional particle accelerator. The US scientists hope that they will soon be able to replace miles-long accelerators with compact accelerators that can fit on top of a table.
The results of the experiment were published this week in Physical Review Letters.
To reach such speeds, researchers used a petawatt laser (a petawatt equals a quadrillion watts of power) and a 9-centimeter-long tube of super-charged plasma particles. The electrons in the plasma tube reached a speed equivalent to 4.25 giga-electron volts.
“This result requires exquisite control over the laser and the plasma,”
Dr. Wim Leemans, lead author of the Berkeley Lab experiment, said.
Traditional particle accelerators such as CERN’s 17 mile-long colliders, use electric fields to speed up particles, instead of lasers, and have a speed limit of about 100 mega-electron volts before they break down.
Compact laser-plasma accelerators use a laser beam that goes through a very thin tube loaded with plasma. The laser beam creates a micro-tunnel in the tube and a wave field that attracts electrons and makes them accelerate to high energies. Scientists say that what happens in the plasma tube is very similar to what happens to a surfer when accelerating down the face of a wave.
The 4.25 giga-electron volts were achieved by one of the most powerful lasers on Earth. Its name is BELLA (Berkeley Lab Laser Accelerator) and can easily produce a petawatt of power.
Dr. James Symons, associate researcher at Berkeley Lab, said this was an extraordinary achievement for Dr Wim Leemans and his colleagues to have such record breaking results in their first BELLA operation.
Dr Leemans has also said that BELLA wasn’t just powerful, but it also was very precise:
“We’re forcing this laser beam into a 500 micron hole about 14 meters away. The BELLA laser beam has sufficiently high pointing stability to allow us to use it.”
BELLA has a laser pulse that fires once in a second with a precision of a fraction of a percent. With many others this couldn’t have been achieved, Dr Leemans explained.
However, before switching on BELLA, researchers used a computer simulation to see the probable outcome of the experiment. For this purpose, they used an high performing computer at the National Energy Research Scientific Computing Center (NERSC) in Oakland, California. Scientists said that they had to use this simulation because working at such a small scale any small change could stir great perturbations.
In the near future, Dr Leemans and his team said they planed to obtain 10 giga-electron volts from BELLA.