A particle accelerator that can fit on top of a table has been designed and built by physicists from the University of Texas at Austin. The energy and velocities generated in this new tiny device are comparable to those produced by much larger machines, some of which are up to 600 feet long.
The new accelerator is based on a process known as laser-plasma acceleration, an idea first conceived in the 1970's. It works by having a powerful, short blast from a laser excite a sample of gas in order to separate and excite electrons. Physicists have been working on practical versions of the idea since the 1990's, but practical lasers have never been powerful enough to initiate the process.
The team took advantage of the Texas Petawatt Laser, one of the most powerful such devices in the world.
"We have accelerated about half a billion electrons to 2 gigaelectronvolts over a distance of about 1 inch. Until now, that degree of energy and focus has required a conventional accelerator that stretches more than the length of two football fields. It's a downsizing of a factor of approximately 10,000," Mike Downer, professor of physics in the College of Natural Sciences, said.
Particle accelrators, just a few inches long, could produce energies in the range of 10 GeV in the next few years, according to Downer. Current designs of these X-ray free electron lasers, the most powerful X-ray macines in the world, are hundreds of times larger. This 10 GeV mark would an important milestone, as these are the energy levels which produce X-rays suitable for a wide variety of scientific applications. In an additional boost to the technology, petawatt lasers, which produce energies equal to billions of megawatts, are now available for commercial purchase. Simulation suggest that similar devices with energies in the 10 GeV range could be designed using the same technology and current lasers.
"To a layman it looks like low technology. All you do is make a little puff of gas with the right density and profile. The laser pulse comes in. It ionizes that gas and makes the plasma, but it also imprints structure in it. It separates electrons from the ion background and creates these enormous internal space-charge fields. Then the charged particles emerge right out of the plasma, get trapped in those fields, which are racing along at nearly the speed of light with that laser pulse, and accelerate in them," Downer said.
Development of the small accelerators could herald a day when even small academic and research facilities will be able to afford and house particle accelerators, and be able to harness the powerful X-rays that these machines can produce. By using these high-energy wavelengths, biologists can easily study life at an atomic scale.
Construction of the miniature accelerator is profiled in the journal Nature Communications.
