In 1962, in the rolling hills west of Stanford University, construction began on the longest and straightest structure in the world. The linear particle accelerator – first dubbed Project M and affectionately known as "the Monster" to the scientists who conjured it – would accelerate electrons to nearly the speed of light for groundbreaking experiments in creating, identifying and studying subatomic particles.

SLAC would go on to become a multi-program lab and a world leader in X-ray and ultrafast science, diversifying its scientific mission to include cosmology and astrophysics, materials and environmental sciences, biology, sustainable chemistry and energy research, scientific computing and more.

Historical timeline

Stanford University leased land to the federal government for construction of the new Stanford Linear Accelerator Center and provided the brainpower for the project. This set the stage for a productive and unique scientific partnership that continues today, made possible by the sustained support and oversight of the U.S. Department of Energy.

Four Nobel prizes have been awarded to six scientists for research at SLAC that discovered two fundamental particles, proved protons are made of quarks and showed how DNA directs protein manufacturing in cells.

The hunting of the quarks

Scientists have known since the 1930s that an atom’s nucleus contains protons and neutrons. But were these made of even smaller particles? Some theorists thought so; but by the late 1960s no trace of these theoretical building blocks, whimsically named quarks, had been found.

In 1967, a team of SLAC and MIT scientists began using electron beams with record high energies from the 2-mile-long SLAC linear accelerator to probe the nuclei of hydrogen and deuterium atoms. At first they saw nothing unusual. But when they switched to a technique called “inelastic scattering,” they were surprised to see electrons scattering off “hard grains” in the centers of protons and neutrons. Those hard grains were the up and down quarks that theorists had predicted years before.

In 1990 the Nobel Prize in physics was awarded to the leaders of the experiments – Richard E. Taylor of SLAC and Stanford and Jerome I. Friedman and Henry W. Kendall of MIT.

The electron’s heavy cousin

When SLAC’s 2-mile-long linear accelerator turned on in 1962, scientists had identified two families of fundamental particles that each contained two leptons, including the familiar electron that orbits the nucleus of atoms. 

There was no reason to think a third family of particles existed. But SLAC’s Martin Perl wondered: Why not? 

He immediately started searching for a third family at the new accelerator. When the powerful SPEAR collider became available in 1973, he began looking there, too, in the debris from electron-positron collisions. 

In 1975, after years of persistent trying in the face of widespread skepticism, Perl discovered the first member of the third particle family – the tau lepton, which is 3,500 times more massive than its cousin, the electron. In 1995 he shared the Nobel Prize in physics.

The discovery inspired other scientists to go looking for two quarks and a neutrino to round out the third particle family. By 2000 they discovered all three.

The fourth quark is a charm

On November 11, 1974, two rival scientific teams announced that they had independently discovered the same particle at two of the world’s most powerful accelerators. 
SLAC’s Burton Richter and his colleagues found it by colliding electrons and their antimatter opposites, positrons, in the lab’s SPEAR ring. They named the new particle “psi.” Samuel C.C. Ting’s MIT team found it by smashing protons into a beryllium target at Brookhaven National Laboratory. They named the new particle “J.” Scientists eventually agreed to call it J/psi. 

Why was J/psi such a big deal? Because it’s made up of a charm quark and its antimatter opposite, anti-charm – and its discovery was the first demonstration that the charm quark actually existed. Charm was the fourth of the six known quarks to be discovered. 

For their photo-finish discoveries, Richter and Ting shared the 1976 Nobel Prize in physics.

Translating life’s code into action 

The instructions contained in our DNA would be useless without a way to carry them out. The first step in doing that is transcription. It copies the genetic instructions in DNA onto messenger RNA, which ferries them to the cellular factories where proteins are made.

Many illnesses are linked to hitches in transcription, and an interruption in this process can be fatal.
Roger Kornberg began studying the cell’s transcription apparatus in the 1970s. By 2001 his team at Stanford University School of Medicine had crystallized all the complicated molecules involved and probed their structures with X-rays at SLAC’s Stanford Synchrotron Radiation Lightsource and similar facilities. 

They created the first complete picture of transcription in action for cells that have nuclei, like those found in mammals and yeast. It’s so detailed that you can distinguish individual atoms, making it possible to understand how transcription works and how it is regulated. For this work, Kornberg received the 2006 Nobel Prize in chemistry.

In SLAC’s initial experiments, accelerated electrons were fired into stationary targets. Colliders allowed scientists to smash electrons and positrons into each other head-on at the much higher energies needed to reshape our understanding of matter.

The Stanford Positron Electron Asymmetric Ring (SPEAR), completed in 1972, was the lab’s first collider - a ring 80 meters in diameter where accelerated electrons and positrons could be brought into collision at unprecedented energies. This allowed scientists to discover three fundamental particles that were the basis of Nobel prizes.

The Positron-Electron Project (PEP), a collider ring with a diameter almost 10 times larger than SPEAR, ran from 1980-90. The Stanford Linear Collider (SLC), completed in 1987, allowed scientists to focus electron and positron beams from the original linear accelerator into micron-sized spots for collisions. The SLC hosted a decade of seminal experiments.

PEP-II, the follow-on to PEP, included a set of two storage rings and operated from 1998-2008.

Synchrotron research and an X-ray laser

The Stanford Synchrotron Radiation Project, which opened to visiting researchers in 1974, used electromagnetic radiation generated by particles circling in SPEAR to explore samples at a molecular scale. Its modernized descendant, the Stanford Synchrotron Radiation Lightsource (SSRL), now supports 30 experimental stations and about 2,000 visiting researchers a year. SPEAR, now known as SPEAR3 following a series of upgrades, became dedicated to SSRL operations in 1992.

Roger D. Kornberg, professor of structural biology at Stanford, received the Nobel Prize in chemistry in 2006 for work detailing how the genetic code in DNA is read and converted into a message that directs protein synthesis. Key aspects of that research were carried out at SSRL.

Meanwhile, sections of the linear accelerator that defined the lab and its mission in its formative years are still driving electron beams today as the high-energy backbone of two cutting-edge facilities: the world's first hard X-ray free-electron laser, the Linac Coherent Light Source (LCLS), which began operating in 2009, and FACET-II, a test bed for next-generation accelerator technologies.

SLAC's scientific mission has diversified from an original focus on particle physics and accelerator science to include cosmology, materials and environmental sciences, biology, sustainable chemistry and energy research, scientific computing and more. The lab is also a world leader in X-ray and ultrafast science.

Scientists still come by the thousands to use lab facilities for an even broader spectrum of experiments, from archaeology to drug development, industrial applications and even the analysis of dinosaur fossils and art objects. Much of this diversity in world-class experiments is based on continuing modernizations at SSRL and the unique capabilities of LCLS.

Our global reach

Today our research truly has a global reach. 

Our experimental footprint stretches from Latin America to Europe to the South Pole, from a Canadian nickel mine 6,800 feet below ground to a space telescope orbiting 300 miles overhead. We’re building the world’s biggest camera for ground-based astronomy; looking for patterns left by cosmic inflation in the first trillionth of a trillionth of a trillionth of a second after the Big Bang; and playing a leading role in searches for dark matter, dark energy and fundamental particles, whose discovery could poke holes in the Standard Model that describes all the known particles and forces. 

By advancing the understanding of how nature and technology work at the largest, smallest and most fundamental levels and learning how to manipulate and control matter at the scale of atoms and electrons, we’re laying the foundation for both scientific impact and practical innovations.