Laser-plasma accelerator could generate bright X-rays for biological imaging, simulations show

Bright X-rays in the 2.3 to 4.4 nanometer range, known as the "water window," are ideal for examining biological samples in their natural aqueous environment. Traditionally, generating this type of radiation at the necessary quality and intensity has been technically challenging, as only free-electron lasers in large-scale accelerator systems can produce it.

A research team from Heinrich Heine University Düsseldorf (HHU), ELI Beamlines in the Czech Republic, and the University of Strathclyde have demonstrated through simulations that laser-plasma-based particle accelerators can provide easy access to this radiation range. Biological systems largely consist of water, while biological molecules contain elements like carbon and nitrogen, which absorb electromagnetic radiation strongly, making water-window X-rays particularly useful.

Dr. Bernhard Hidding, leader of the strong-field laser plasma physics group at HHU, explains that free-electron laser systems, which have been used to obtain bright X-ray radiation for biological examinations, require kilometer-long setups. To overcome this limitation, the research team proposes using a compact electron accelerator based on laser-plasma technology, developed in Düsseldorf.

In a laser-plasma accelerator, a high-intensity laser pulse creates a plasma wave in a gas, generating extremely high-field intensity that can accelerate electrons to near-light speed in just a few centimeters. The simulations show that the ultrabright electron pulses in magnetic undulators can produce X-ray flashes, converting nearly all of the electron's energy into X-ray energy, within just a few meters.

The process is expected to be robust and adjustable. Dr. Fahim Habib, principal investigator at the ELI research facility, notes that the quality of the electron beams primarily determines whether such a radiation source can function as a free-electron laser. The study indicates that a novel hybrid laser-plasma accelerator could create the necessary conditions.

Given the compact size and significantly lower cost compared to conventional particle accelerators, the system could be deployed at universities, research facilities, or for commercial applications. As such a system is compact and cost-effective, it could be situated at universities and research facilities or used for commercial purposes, expanding water-window X-ray imaging and spectroscopy from a few major national laboratories to a broader research landscape.