Scientists at the University of Osaka have achieved a major advance toward building much smaller particle accelerators. Using high-intensity lasers, they demonstrated free-electron laser amplification in the extreme ultraviolet range, between 27 and 50 nanometers. The entire acceleration process took place over just a few millimeters instead of the hundreds of meters required by conventional machines.
The researchers used a method called laser wakefield acceleration. In this technique, an intense laser pulse travels through a gas and creates waves in the resulting plasma, similar to the wake behind a speedboat. These plasma waves generate extremely strong electric fields - more than 1000 times stronger than those in ordinary accelerators. The strong fields rapidly push electrons to high energies. By shaping the laser pulse carefully and using specially designed supersonic gas nozzles, the scientists created more stable plasma waves and produced high-quality electron beams in which all electrons have nearly the same energy.
Miniaturizing powerful light sources for everyday labs
This stable, monoenergetic electron beam allowed the system to amplify light as a free-electron laser at extreme ultraviolet wavelengths. Free-electron lasers produce very bright, coherent light with extremely short pulses. Reaching these wavelengths is an important milestone on the path to even shorter x-ray wavelengths. Compact x-ray free-electron lasers could eventually generate light 10 billion times brighter than the sun in pulses lasting only femtoseconds, or quadrillionths of a second.
Conventional accelerators and free-electron lasers are huge facilities that few laboratories can access. The new results show that laser wakefield acceleration can deliver performance close to what practical high-quality accelerators need, while dramatically reducing size. Greater stability of the plasma removes a long-standing barrier that had made the technology seem impractical.
Such desktop-sized instruments would make advanced research possible in ordinary laboratories. Fields such as life sciences, materials science, semiconductor development, and quantum science could benefit greatly. The work brings compact, high-performance x-ray sources closer to reality and opens the door for widespread use of powerful light tools that today require massive national facilities.
This study is published in Physical Review Research.