Nov 22, 2023 · By Erik Olsen

SLAC, the Two-Mile Machine Behind Stanford That Changed Physics

SLAC National Accelerator Laboratory, near Stanford, helped discover quarks, hosted the first U.S. website and built the world’s largest digital camera. Today its X-ray lasers film chemistry in action.

Updated Oct 12, 2026

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(Peter Ginter/SLAC National Accelerator Laboratory)

In the hills behind Stanford, next to Interstate 280, there’s a building two miles long. Most of the people who drive past it every day have no idea what it is. It’s the SLAC National Accelerator Laboratory, and some of the most important physics of the last 60 years happened inside it.

SLAC opened in 1962 as the Stanford Linear Accelerator Center. Work done there has earned six scientists four Nobel Prizes, for discovering two fundamental particles, showing that protons are made of quarks, and figuring out how cells read DNA to make proteins.

Stanford’s Roger Kornberg received the 2006 chemistry Nobel for showing how DNA is transcribed into RNA, shown on screens.
(Peter Ginter/SLAC National Accelerator Laboratory)

Stanford runs the lab for the U.S. Department of Energy, and these days it does a lot more than particle physics: chemistry, biology, materials science, medicine and astronomy. Its main tools are extremely bright X-rays, made with synchrotron radiation and a free-electron laser.

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The heart of the place is the 2-mile (3.2-kilometer) linear accelerator, finished in 1966. It was the longest in the world, and it fires electrons in a straight line at nearly the speed of light. Experiments there found the charm quark in 1974 and the tau lepton in 1975, and showed that protons and neutrons have quarks inside them. All three led to Nobel Prizes in Physics, in 1976, 1990 and 1995.

SLAC has a place in computer history too. The Homebrew Computer Club, where a lot of the personal computer revolution got started, met there, and it’s where Steve Wozniak showed off the prototype Apple-1 in 1976.

Steve Jobs and Steve Wozniak Apple 1

In December 1991, SLAC also put up the first website server outside Europe. Through the 1990s, its Stanford Linear Collider studied the Z boson, one of the particles that carries the weak nuclear force.

The work keeps going. In November 2023, SLAC and Toyota announced progress on cheaper, more efficient fuel cells.

The star of the lab now is the Linac Coherent Light Source, or LCLS, an X-ray laser that has been running since 2009. In September 2023, SLAC switched on its upgrade, LCLS-II, the most powerful X-ray laser in the world, for research on everything from quantum materials to cleaner batteries to medicine.

“This achievement marks the culmination of over a decade of work,” said LCLS-II Project Director Greg Hays. “It shows that all the different elements of LCLS-II are working in harmony to produce X-ray laser light in an entirely new mode of operation.”

SLAC built the first hard X-ray free-electron lasers. Think of them as X-ray strobe lights. They fire flashes so bright and so short that scientists can freeze atoms and molecules in the middle of a chemical reaction. That’s let researchers make the first “molecular movie” of a reaction, catch the exact moment plants split water to release oxygen, and recreate the crushing conditions inside planets, where carbon can rain down as diamonds.

As of 2021, about 1,600 people from 55 countries worked at SLAC, along with 470 postdocs and graduate students, and more than 3,000 visiting scientists come through every year. Besides the X-ray laser, they use the Stanford Synchrotron Radiation Lightsource for materials and biology research, and SLAC helps run the main instrument on NASA’s Fermi Gamma-ray Space Telescope.

After decades of effort and help from SLAC’s X-ray laser, scientists have finally seen the process by which nature creates the oxygen we breathe. (SLAC)

SLAC also built the biggest digital camera in the world. It’s the 3.2-gigapixel camera for the Vera C. Rubin Observatory on a mountaintop in Chile, which saw first light in 2025. Each shot covers a patch of sky about 40 times the size of the full moon, and over 10 years it will photograph the entire southern sky again and again, building an enormous movie of the universe to help astronomers study dark matter, dark energy and how galaxies form.

SLAC has developed the world’s largest digital camera for the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST)

In 2008, the lab changed its name to SLAC National Accelerator Laboratory to reflect how much more it does now. It got $68.3 million in Recovery Act money in 2009, and it teamed up with Stanford on Bits and Watts, a project to build a cleaner, smarter power grid.

Particle physics hasn’t gone anywhere, either. At FACET, scientists are working on plasma accelerators, which could someday do the job of SLAC’s two-mile machine in a fraction of the space. The lab’s original accelerator was powered by klystrons, high-power microwave tubes first developed at Stanford. And SLAC’s X-rays have even helped read history: in the 2000s, scientists at its synchrotron used them to reveal hidden text in the Archimedes Palimpsest, a medieval prayer book written over a copy of lost works by Archimedes.

Archimedes Palimpsest (Wikipedia)

Other recent work includes a new way of turning seawater into hydrogen fuel, research on nitroxide, a molecule with possible medical uses, and running superconducting X-ray lasers at temperatures colder than outer space.

So next time you’re on 280 near Menlo Park and pass that long, low building in the hills, now you know. That’s where quarks were found, where the web first came to America and where scientists now watch chemistry happen one atom at a time.