The Lawrence Berkeley National Laboratory’s BELLA laser system set a world record on July 20 for reaching a petawatt of power — a quadrillion watts — in a pulse only 40 quadrillionths of a second long.
This achievement is being hailed as a landmark in the field of particle acceleration due to the ability of BELLA — the Berkeley Lab Laser Accelerator — to pack such a large amount of power into each pulse while maintaining a pulse rate of one hertz, or one pulse per second — far more frequent than a traditional high-power laser system.
“Particle accelerators are these amazing things, kind of like the ultimate microscopes,” said Mark Hogan, head of the Advanced Accelerator Research Department at the Stanford Linear Accelerator Center. “In one sense, we use them to study the smallest particles and forces in the universe and figure out how the universe was made and why it behaves the way it does.”
Accelerators capable of making high-power electron beams tend to be the most useful in research of this type, but they also the largest and most expensive. Unlike the technology used in BELLA, glass is used to magnify electron beams in these conventional accelerators, according to Wim Leemans, head of the Lasers and Optical Accelerator Systems Integrated Studies (LOASIS) Program at Berkeley Lab, which is working on the BELLA project.
“The name of the game is to control the amount of heating,” Leemans said. “All of the glass-based systems around the world — and there are a few that have reached a petawatt — fire maybe once every hour because the glass has to cool down after every shot, whereas (the materials we use) have no issue with that.”
LOASIS plans to further develop BELLA into an accelerator roughly one foot in length that is capable of producing a 10 billion-electron volt beam, something of such high power that it would require an accelerator five to six football fields in length using conventional technology. According to Leemans, BELLA will be the accelerator’s “drive source.”
“We are using the light pulse (from the laser) to excite very large electric fields in a plasma medium. Those large electric fields allow electrons to be accelerated just like surfers would be accelerated by the wave behind a motorboat,” Leemans said.
The lasers, built by French scientific manufacturer Thales Group, are capable of being fired frequently enough to allow scientists to collect data at a much quicker rate, therefore speeding up development of the system in turning it into a useful tool.
“The compact accelerators we are now leading the way in developing could open exciting new possibilities for doctors, universities and industry to use these tools for advanced treatment and research techniques,” said Paul Alivisatos, director of Berkeley Lab. “Compact accelerators could also pave the way to the next generation of particle colliders for high-energy physics.”
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