Physicists at SLAC National Accelerator Laboratory in the US have shattered the record for most powerful beam of electrons, cramming an ultra-high current of around 100,000 amps into an instant.
At around five times the field strength of what could be achieved previously, the mind-blowing amount of energy in the beam’s electric field at SLAC’s FACET-II linear accelerator could push the boundaries on experimentation, leading to new discoveries in everything from astrophysics to materials science.
The team’s new technique for steering millimeter-long chains of electrons along a magnetic track allows them to squeeze the race down into a photo finish that delivers more than a petawatt of power in one million-billionth of a second.
Particle accelerators have been a vital tool for physicists for nearly a century, using oscillating electromagnetic fields to nudge charged particles up to velocities that come within a whisker of the speed of light.
As the particles change direction their own field shines with high-energy X-ray photons that can illuminate materials for high-resolution imagery.
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Place another wall of electromagnetism in front of this beam, the energy from the colliding fields could shake a variety of shiny new particles from the quantum foam itself.
To create more intense flashes or light, or bigger collisions, more energy is needed; either by pushing the particles ever faster, or by ensuring all their energy is delivered in a shorter period of time.
Since the electrons are already traveling at near top velocities as they surf on waves of electromagnetism, more speed isn’t possible. By the same reasoning, forcing electrons at the back of the pack to press down on their accelerator and catch up to those in front isn’t a solution.
But there is another trick. Though they’re all racing at the same speed, the accelerator’s electrons are distributed along the slope of an electromagnetic wave as they surf down the tunnel, with some at the ‘bottom’ and some at the ‘top’.
Those at the top have more energy whenever they swerve. To force those at the bottom to slow, the researchers needed a way for them to pump the brakes a touch.
One way commonly used to manage such a situation is the use of a magnetic obstacle that causes lower energy particles to take a slightly longer path, much as a chicane on an actual race track would force a less powerful car to carefully weave left and right while a car with more grunt could push straight through.
By deflecting particles according to their energy level, the chain of electrons could bunch up and – in theory – pack a greater punch.
There’s just one problem. Every swerve on the track forces the electrons to shed precious energy in the form of a high-frequency X-ray photon.
To help replace the lost energy, the team inserted into the middle of the chicanes a second magnetic device called an undulator, which pushed the electrons back and forth quickly in another direction. At the same time, a flash of light from a sapphire laser was introduced to control the spread of electrons.
The timely mix of undulations and light shaped the distribution of the chain as it was repeatedly sped up and compressed, replacing a portion of the lost energy while forcing a number of the electrons to overlap within a space barely a third of a micrometer long.
The end result was a powerful lightning in a bottle created with a technique that could be improved upon in future, potentially confining more high-speed electrons to an even smaller space.
This research was published in Physical Review Letters.
