Physicists at the SLAC National Accelerator Laboratory just created a petawatt laser beam with the highest peak power and current ever.
This beam was formed from a bunch of electrons that were compressed and modified to create the ultimate energetic pulse.
In the future, laser beams like this could be used as a light source or to study the nature of empty space by ripping particles out of it.
Try to fathom the power of 1 million nuclear power plants. Now, imagine there is a way to pack the equivalent of that into the pulse of a laser beam—even if it’s only for one quadrillionth of a second.
Well, as of recently, there’s no longer a need to simply imagine—scientists have given us the newest glimpse of what a petawatt laser (a petawatt equals one quadrillion watts) is capable of. When you have one quadrillion watts at your disposal, you can create the extreme conditions found deep inside planets or split atoms to produce gamma rays. A team of researchers at SLAC National Accelerator Laboratory just leveled that up to an electron laser beam that could possibly shred matter and tear particles and antiparticles out of empty space.
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Led by SLAC accelerator physicist Claudio Emma, the research team was able to take a lot of electrons (a collection measuring about a millimeter long) and accelerate them into beams that generated the highest current and peak power ever.
“Femtosecond-level control of ultra-high current beams is a powerful tool for optimizing next generation beam interactions relevant across scientific disciplines,” the team wrote in a study recently published in Physical Review Letters.
How did they do it? Think of the particle accelerator as a pinball machine in multiball phase, except the balls are electrons moving at nearly the speed of light. Instead of ramps and curves, electrons are accelerated by radio waves through a vacuum chamber. Just like a pinball will swerve when it hits a curve, so electrons will change direction when they run into a magnetic field. If one ball is traveling slower, it will follow the curve, but the faster a ball is moving, the more of that curve it will just sort of hop over. Electrons in a magnetic field do the same thing.
Say the pinballs have to climb a ramp before ending up on a curve, except the ramp is made of radio waves. The electrons in front are going to be traveling along a less steep part of the wave than those in the back, which means they are going to arrive at the top of the ramp with less energy than the ones behind them. This results in a chirp—a signal whose frequency increases (up-chirp) or decreases (down-chirp) over time. In this case, it increased. And laser pulses can create especially fast chirps.
When the chirp occurred, Emma’s team compressed the bunch of electrons by firing them through a structure similar to a lane in a pinball machine that makes the ball swerve to the left and right. This is known as a chicane. The chicane in this experiment used magnets to force the beam to swerve, and since lower-energy electrons are deflected by the magnets more than higher-energy electrons, those with lower energy have to round the curves more. This makes them travel longer and further than those that have higher energy, but are still behind.
What the chicane ultimately does is give the high-energy electrons a chance to catch up and compress the entire bunch. But here, the experiment takes a turn. Shortening a bunch of electrons needs further manipulation, so the team moved on to an undulator magnet, which uses rows of dipole magnets that have closed magnetic fields which loop through both ends. These magnets keep alternating the direction the overall magnetic field is going in, wiggling the electrons back and forth.
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The researchers then used a low-energy laser light to sculpt the electron bunch. As the electrons wiggled, they exchanged energy with that light, which led to an extra chirp being created in the middle. The bunch continued through three more chicanes in this sophisticated pinball machine, alternating between acceleration and compression over and over. The extra chirp became much more intense and produced a pulse with a mind-melting amount of energy.
And Emma doesn’t want to stop there. “We generated 100-kiloamp beams, now the next step is getting to mega-amp beams,” he said in a press release. He sees these types of beams as being a potential light source, along with potentially ripping particles out of thin air to examine the nature of empty space.
Whatever an electron beam this powerful can used for in the future, it sure plays a mean pinball.
Headshot of Jackie Appel
Jackie is a writer and editor from Pennsylvania. She's especially fond of writing about space and physics, and loves sharing the weird wonders of the universe with anyone who wants to listen. She is supervised in her home office by her two cats.