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A plasma-based device is set to challenge particle accelerators that generate high-quality light pulses, with evidence that the cheaper plasma platform can run at competitive repetition rates.
Particle accelerators are usually associated with the discovery of fundamental particles, but they also have a long history of powering light sources. One such source is the free-electron laser, in which a high-energy beam of electrons from a linear accelerator generates ultrashort X-ray laser pulses by travelling through a series of magnets. However, conventional accelerators are expensive and unwieldy, needing up to one kilometre of space under Earth’s surface, and a smaller, cheaper accelerator based on plasma (ionized gas) might be capable of doing the job. The plasma in such a device needs to settle before each new interaction with the electron beam, but the interactions must be repeated at a high rate to power a free-electron laser that has sufficient average brilliance. Writing in Nature, D’Arcy et al.1 report that the maximum repetition rate of a plasma-based accelerator could be as high as one million times per second — or even higher, putting it comfortably in the realm of nearly all potential applications.