This Foot-Long Box Is the Most Advanced Particle Collider in the World
‘Plasma surfing’ accelerates particles 500 times faster than traditional methods.
That metal box is the accelerator. Image: SLAC National Accelerator Laboratory
The CERN particle collider is 17 miles long. China just announced a supercollider that is supposed to be roughly 49 miles long. The United States' new particle collider is just under 12 inches long.
What it lacks in size, it makes up for in having a bunch of plasma inside of it, allowing researchers at the SLAC National Accelerator Laboratory in Menlo Park, Calif., to accelerate particles more than 500 times faster than traditional methods. In a recent test published in Nature, Michael Litos and his team were able to accelerate bunches of electrons to near the speed of light within this tiny chamber.
"If you want to build a next generation high energy physics particle collider, there are two ways of thinking," Litos told me.
First, he said, you could build them even bigger than the Large Hadron Collider or the proposed followup, Compact Linear Collider, which is supposed to be 31 miles long. "Or, you can build a comparable machine that reduces the physical footprint by an order of magnitude by taking information we know about plasma wakefield acceleration and using it," he told me. "All of a sudden, a 50 kilometer accelerator becomes something like 5 kilometers."
To be clear, the foot-long collider in Menlo Park isn't looking for the Higgs Boson or performing any of the important work that CERN has been doing. The Large Hadron Collider is still certainly the most useful particle collider, but this one is probably going to be the technology that fuels the next generation of supercolliders. It's a proof-of-concept that shows that to build next generation particle colliders, we don't necessarily need gigantic underground tunnels.
In a traditional particle collider, beams of electrons are launched down a large vacuum tube using electromagnetic fields. In doing so, lots of energy is needed to constantly accelerate the electrons, which is why the tubes themselves are often so massive.
But by filling the tube with plasma (in this case, using a specialized oven created by researchers at UCLA), energy can be passed from one electron bunch (the drive bunch) back to ones behind it (the trailing bunch). Each time you do this, the trailing electrons get faster.
"We send them in right after another. The first gives up its energy to the second bunch, and we can accelerate these much faster in a shorter distance," Litos said. "If you repeat this many, many times, you can scale this up to make an application-driven collider."
And that's the plan, at the moment. Litos is trying to make it easier to actually create the plasma within the tube by filling it with hydrogen, then using a simple laser to zap it, ionizing it. From there, the tech can be put into larger colliders, and then real particle hunting can begin.
"Right now this is basic research, but we're checking things off the checklist," Litos said. "We can provide a beam with a large energy boost in a short distance. We can accelerate an entire bunch of billions of electrons, and we can do it with a small energy spread."
Though there's certainly a long road ahead, the technology appears sound. In an accompanying news and views article, Mike Downer and Rafal Zgadzaj of the University of Texas at Austin write that the team has "overcome one of the most difficult challenges so far in the long quest for small, affordable accelerators, and have given the plasma-surfing community every reason to surge ahead."