How Synchrotrons Work—the World's Brightest Light

What Is a Synchrotron?

A synchrotron light source is a massive, ring-shaped machine that accelerates electrons to nearly the speed of light and harvests the intense radiation they emit when forced to change direction. The result is an extraordinarily bright beam of X-rays—billions of times brighter than the sun—that scientists aim at everything from ancient fossils to experimental drugs.

More than 50 synchrotron facilities operate or are under construction worldwide, from the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, to the Diamond Light Source in Oxfordshire, England, and the Australian Synchrotron near Melbourne. They serve tens of thousands of researchers every year.

How the Machine Works

The process begins with an electron gun, which fires a stream of electrons into a linear accelerator. Here, the particles are boosted to near-light speed—typically 99.9997 percent of c. A smaller booster ring ramps their energy further, often from around 100 MeV to 3,000 MeV in under a second.

The electrons then enter the storage ring, a polygon-shaped vacuum tube that can stretch hundreds of meters in circumference. Powerful bending magnets steer the electrons around the ring's curves. Each time the particles change direction, they shed energy in the form of electromagnetic radiation—synchrotron light.

To intensify the beam, many facilities insert devices called undulators or wigglers into straight sections of the ring. These arrays of alternating magnets force electrons to oscillate rapidly, producing even brighter, more focused X-rays. The light is channeled down dozens of beamlines—individual experimental stations radiating outward from the ring like spokes from a wheel.

Why Synchrotron Light Is Special

Ordinary X-ray machines produce a broad, relatively dim beam. A synchrotron, by contrast, delivers light that is:

• Extremely bright — up to 10 billion times more intense than conventional sources
• Highly focused — beams can be narrowed to less than a micrometer across
• Tunable — scientists can select precise wavelengths, from infrared through ultraviolet to hard X-rays
• Pulsed — the beam arrives in ultrashort bursts, enabling time-resolved experiments that capture chemical reactions in real time

These properties let researchers see structures and processes that are invisible to any other instrument.

What Synchrotrons Have Revealed

Medicine and Drug Design

Synchrotron X-ray crystallography was essential for mapping the structure of the SARS-CoV-2 virus spike protein, accelerating COVID-19 vaccine and antiviral development. The technique routinely helps pharmaceutical companies visualize how drug molecules dock with disease targets at the atomic level.

Paleontology

Phase-contrast microtomography at synchrotron facilities has revealed soft tissues inside 300-million-year-old fossils, uncovered embryo bones inside 125-million-year-old lizard eggs, and read invisible ink on ancient parchments. A recent study used synchrotron imaging to reclassify the world's "oldest octopus" fossil as a nautilus relative, solving a decades-old evolutionary puzzle.

Materials Science

Engineers use synchrotron beams to watch stress fractures propagate through jet-engine turbine blades, study battery electrodes as they charge and discharge, and map the chemical composition of next-generation solar cells—all without destroying the sample.

The Next Generation

Fourth-generation synchrotrons, such as the upgraded ESRF-EBS in Grenoble and Brazil's Sirius facility, use a multi-bend achromat lattice design that squeezes the electron beam into an even thinner ribbon. The result is light up to 100 times brighter than previous machines, opening the door to imaging single molecules and tracking chemical reactions on the femtosecond timescale.

As long as scientists need to see the invisible—whether inside a living cell, a meteorite, or an ancient manuscript—synchrotrons will remain one of the most powerful tools in the research arsenal.