Researchers at Osaka University have achieved an important milestone in the development of a tabletop X-ray laser, with the goal of building an ultra-compact high-energy electron accelerator.
Researchers have taken an important step toward miniaturizing particle accelerators by demonstrating free-electron laser amplification at extreme ultraviolet wavelengths using high-intensity lasers.
By producing a high-quality monoenergetic electron beam (i.e., a beam in which all electrons have approximately the same energy), we achieved an important milestone toward compact accelerator technology.
“Our work provides several significant improvements over previous techniques, making it possible to achieve free-electron laser amplification at extreme ultraviolet wavelengths,” said first author Zhan Jin.
Generate stronger waves using wakefield acceleration
A research team led by the Osaka University Institute of Scientific and Industrial Research (SANKEN) used a technique called laser wakefield acceleration to generate plasma waves that generate extremely strong accelerating electric fields thanks to waves within the plasma that travel at nearly the speed of light.
These electric fields are more than 1000 times more powerful than those of conventional particle accelerators.
Jin explained, “We used laser pulse shaping to improve focusing accuracy. When combined with a specially developed supersonic gas nozzle, we can create a more stable wavefront, allowing precise control of the plasma source.”
More practical and high quality particle accelerator
Using free electron laser amplification in this way is essential to reducing the distance required to accelerate electrons.
Traditional systems require distances of hundreds of meters, but the powerful fields generated by laser wakefield acceleration have the potential to reduce this to just millimeters.
These results demonstrate that laser wakefield acceleration approaches the performance required for practical high-quality electron particle accelerators. Demonstrating this at extreme ultraviolet wavelengths is an important milestone, but the research team intends to take this further.
Aiming for a small electronic free laser
Demonstrating free-electron laser operation in the extreme ultraviolet region is an important first step toward extending the technology to shorter wavelengths and ultimately enabling compact X-ray free-electron lasers.
These extremely powerful light sources produce coherent X-rays that are 10 billion times brighter than the sun, producing ultrashort femtosecond pulses.
Currently, their use is limited to large facilities, but miniaturization of these lasers will allow them to be used in traditional laboratories.
Currently, laser wakefield acceleration is one of the most promising ways to achieve this.
The future of small particle accelerators
Desktop-sized instruments are essential for everyday research, and the development of compact accelerators and X-ray free electron lasers enables advances in fields such as life sciences, materials science, semiconductor development, and quantum science.
Building a desktop-sized accelerator would allow small labs to conduct research that currently requires large-scale accelerator facilities.
“Laser wakefield acceleration has long been considered impractical due to the difficulty of stabilizing the dependent plasma,” explains lead author Tomonao Hosogai.
“We have greatly improved the stability and quality of the electron beam, which will allow future accelerators to be significantly smaller, opening the possibility of creating compact X-ray free electron lasers.”
Overall, this study shows that laser wakefield acceleration may be comparable to practical high-quality, high-energy electron accelerators.
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