See SLAC, a two-mile particle accelerator next to Stanford

SLAC, a two-mile particle accelerator jutting west from Stanford University, pushes electrons near the speed of light. Back when it was still called the Stanford Linear Accelerator, SLAC was used for seminal particle physics discoveries decades ago. 

It's now called the SLAC National Accelerator Laboratory, and its newer mission turns electrons into powerful X-ray lasers at a facility called LCLS (Linac Coherent Light Source). This tunnel links the two LCLS experimental chambers, with X-rays coasting along through the pipes after being generated upstream at a structure called the undulator.

This view from above shows SLAC's linear course underneath Interstate 280, the gently curving roadway. SLAC experimental areas are on the right side of the photo, to the east.

Scientists prepare an experiment at the Soft X-ray Material Science instrument at SLAC's X-ray laser at the LCLS site, which has extended the useful life of the particle accelerator. These researchers are working on an experiment that uses X-ray scattering to study a copper oxide high-temperature superconductor.

SLAC's X-ray Pump Probe (XPP) experiment station uses optical laser light to excite materials that are then studied with X-ray laser pulses. The X-ray laser reveals behavior on ultrashort time scales. Most of the complex equipment in the center here is for the X-ray beam line; the unadorned pipe in the foreground carries another laser beam.

Michael Minitti, head of SLAC's LCLS Soft X-ray Department, shows where laser light emerges to blast targets being studied.

Purple tracks let researchers steer a camera at the X-ray Correlation Spectroscopy (XCS) experiment station through a wide range of angles and distances to measure light scattered off subjects blasted with X-ray lasers.

This section of SLAC shows the basic structure of a linear accelerator: modules built side by side, each giving electrons a bit more of a speed boost. SLAC uses two miles of copper cavities filled with radio waves to push electrons and their antiparticles, positrons, to high speed and high energy.

This above-ground building, called the Klystron Gallery, contains nearly 200 klystrons that generate microwave energy that's piped underground into the accelerator chamber to speed up electrons.

SLAC accelerates electrons and positrons with bursts of high-power microwave energy originating from dozens of devices called klystrons. Each one produces about 60,000 times the power of a kitchen microwave oven. Devices called waveguides, such as the one shown here, direct microwaves from the klystrons to the accelerating cavities.

A quadrupole magnet uses magnetic "lenses" to focus the high-energy electron beams to a width about one-tenth the diameter of a human hair.

SLAC's electron beam must travel through a vacuum, or else acceleration would be limited by short-circuit problems. SLAC operators test each junction carefully for leaks, and those that pass muster are marked with a foil wrapper, as on this vacuum piping. The vacuum has a pressure on the order of one hundred billionth of Earth's atmosphere.

One SLAC research area focuses on reconstructing the formation of the universe. We're familiar with galaxies, but this simulation shows strands of dark matter that lace the cosmos. Galaxies form at the brighter nodes where the density is highest.

This SLAC simulation, run inside a massive supercomputer, shows a phase of the universe's formation when the blasting output from the ionized interstellar hydrogen gas of new stars.

A whiteboard records the illustrated discussions of scientists and engineers at SLAC's X-ray laser experimental facilities.

In a project called FACET, SLAC is experimenting with the use of plasma to accelerate electrons. The plasma -- a high-energy gas made of atoms and their stripped-off electrons -- can be used to accelerate electrons 1,000 times more powerfully than conventional accelerators. This metal box itself is a powerful linear accelerator. SLAC just shut down FACET and is upgrading to FACET-II.

Mark Hogan, scientific leader of the FACET-II project, describes his work in the dimly lit bowels of the SLAC accelerator.

The complicated equipment of the FACET-II project is festooned with data-communication cables.

The original access ladders down to the linear accelerator chambers look like like they belong in a submarine. Nowadays, it's easier to get in, with stairways built in larger access routes that originally were used to lower hardware into the accelerator chamber.

SLAC's linear accelerator stretches in a straight line across the hills of Palo Alto, California. This view looks west toward the front end of the accelerator.

SLAC predates Interstate 280. But knowing the highway was on the way, SLAC built an overpass that lay idle for a few years.

This view shows SLAC's two-mile linear accelerator, looking east from the point where electrons begin their quick trip to near light speed. This end of the accelerator is being upgraded as part of a $1 billion project to boost SLAC's X-ray laser research abilities. In the distance are Stanford University's Hoover Tower and the southern tip of the San Francisco Bay.

This chamber, a vacuum that seals out air, holds samples probed by SLAC's Coherent X-ray Imaging (CXI) experiment station. It's mostly used to study protein crystals. Yes, somebody turned two of the observation ports into eyes for a face, with a grinning mouth below.

Aaron Roodman, an experimental cosmologist, explains SLAC's work on a multi-institution collaboration to build a massive telescope in Chile called the Large Synoptic Survey Telescope (LSST). The camera in the telescope is the size of a small car, and SLAC is building its image sensor. He stands in front of a clean room sealed to keep contaminants away from delicate electronics.

A single 16-megapixel image sensor, one of 189 that SLAC will use to build the LSST, rests under glass in a clean room to avoid contamination.

Here is an illustration of the wide swath of night sky the LSST will be able to photograph in a single image. It's big enough to photograph the entire sky every three or four nights, so astronomers and astrophysicists can track changes in the appearance and position of stars, galaxies and solar system objects. SLAC is assembling the camera's image sensor, made of 189 square, 16-megapixel sensors, each 42mm on edge.

This equipment is used to test the design of sensors in the LUX-ZEPLIN experiment, a multiorganization collaboration to try to detect dark matter.

Hogan describes how SLAC's accelerator components work. The biggest pipe behind him houses laser beams that ensure the accelerator components stay aligned correctly.

When X-ray laser experiments are under way at the LCLS, scientists leave the experimental rooms, close the doors, and oversee the activity from control rooms.

A movable camera is mounted at the far end of a tube at SLAC's X-ray Correlation Spectroscopy (XCS) experiment station, decked with a whimsical "Hello Kitty" label.

Minitti stands by a Rayonix mx170 camera that detects X-rays emitted by a powerful laser at the X-ray Pump Probe (XPP) experiment.

Minitti shows a billion-dollar upgrade under way called LCLS-II, a brighter version of today's LCLS facility.

Visitors to SLAC are greeted with a large aerial photo showing the accelerator stretching in a straight line west of Stanford University and underneath Interstate 280.

A ceramic and stainless steel sculpture called "Star HB113" by Michael Deleon stands in front of the Kavli Institute for Particle Astrophysics and Cosmology at SLAC.