Europe’s X-ray laser set a world record with flashes just 300 attoseconds long

The European X-ray free-electron laser near Hamburg has produced hard X-ray pulses estimated at 300 attoseconds long, and the researchers behind the work say the beam sets a world record for intensity and fluence among attosecond pulses of that kind. During a flash that brief, light covers only about 90 nanometers. Peak intensity exceeded 10²⁰ watts per square centimeter once the beam was focused to a spot 180 by 330 nanometers. Intensity measures power per unit area and fluence measures energy per unit area, so a pulse that leads on both delivers an unusual amount of X-ray light into a very small, very short window.

Tech news in one quick read: Get the most interesting stories in startups, tech and programming, each with a short TLDR, in one daily email from TLDR.

Subscribe to TLDR →

We may earn a commission if you sign up.

The experiment ran in April 2026 and was reported in the journal Optica; one attosecond is a billionth of a billionth of a second. The result gives scientists a sharper tool for watching electrons move inside atoms and molecules.

Focusing to 180 by 330 nanometers with four mirror reflections

European XFEL’s own press release describes the setup at the facility’s MID instrument. An advanced Kirkpatrick-Baez mirror system, with coatings of iridium, squeezed the beam by reflecting each pulse four times, focusing it vertically and horizontally. The resulting spot is about 100,000 times smaller than the cross-section of a human hair. The mirrors came from Japan, where such optics were developed for the LCLS laser in the United States, and the run also used the self-chirping operating mode to raise pulse energy; European XFEL expects its own system in early 2027, funded through a collaboration with the University of Hamburg and Germany’s Federal Ministry of Research, Technology and Space.

First author Ichiro Inoue of the University of Tokyo called the result a world record in intensity and fluence for a hard-X-ray attosecond pulse. Corresponding author Jiawei Yan of DESY noted that generating powerful pulses is only the first step, and that what matters for experiments is what can be delivered to the sample. The author list also includes Jumpei Yamada of the University of Osaka, Ulrike Boesenberg and Makina Yabashi.

Proof from a copper foil

An intensity that high cannot be read off a gauge, so the team used a sample as the check. According to Optica’s news summary, the pulses struck a copper foil 20 micrometers thick, ejecting inner-shell electrons and producing amplified spontaneous emission. That emission appears only when the X-ray intensity is high enough to drive stimulated emission from the vacated inner shells, so its onset and its saturation serve as an independent intensity check. In the process, a cascade in which emitted X-rays stimulate more emission. The signal rose quickly with pulse energy and then saturated at higher energies, which matched the intensity estimated from pulse energy, duration and spot size. Anders Madsen, who leads the MID instrument group, said it was almost magical to see this happen, and described how, once the amplification threshold is crossed, the emitted light condenses into the forward direction.

The 300-attosecond figure is an estimate rather than a direct measurement, as the ScienceDaily report words it, and the record is specific to the intensity and fluence of hard-X-ray attosecond pulses. Records of this kind compare like with like: the claim covers hard X-rays, attosecond duration and the combination of intensity and fluence, and says nothing about softer X-rays or longer flashes. Optica’s news summary appeared on Oct. 21, 2026, and ScienceDaily carried the story on Nov. 4.

From 2024 terawatt pulses to the new mark

The record builds on earlier work. In November 2024 the same facility reported in Nature Photonics, in a paper on a terawatt-attosecond hard X-ray free-electron laser at high repetition rate, a method called self-chirping that delivered terawatt-scale attosecond hard X-ray pulses above 100 microjoules at megahertz repetition rates. That earlier release quoted Gianluca Geloni, who leads the facility’s FEL physics group, saying the approach lets researchers collect data much faster and observe processes that were previously hidden. Yan, also the lead author of the 2024 paper, noted in the new announcement that the earlier demonstration was the starting point.

The facility itself runs 3.4 kilometers underground, with electron energies up to 17.5 GeV, 27,000 pulses per second and X-ray wavelengths from 0.05 to 4.7 nanometers. The new work was published as a peer-reviewed paper in Optica on generating high-fluence, high-intensity hard X-ray attosecond pulses.

The payoff the team describes is concrete: studying how electrons behave in atoms and molecules, exploring nonlinear interactions between intense X-rays and matter, and, over the longer term, learning to control electron motion during chemical reactions. A short pulse can also capture electron information before the X-rays significantly alter the sample. Older approaches to short pulses needed the electron bunch charge cut to tens of picocoulombs, which capped pulse energy; the self-chirping approach keeps the charge unchanged.

The open question is access. The record beam relied on mirrors borrowed from Japan, and European XFEL expects its own mirror system only in early 2027, so routine use by outside research teams depends on that hardware arriving.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

Tech news in one quick read: Subscribe to TLDR →

We may earn a commission if you sign up.