Physics for the rest of us | March 18, 2011 | Palo Alto Weekly | Palo Alto Online |

Palo Alto Weekly

Cover Story - March 18, 2011

Physics for the rest of us

A glossary explaining the work at SLAC


Klystrons are devices that generate microwaves. In a particle accelerator, particles are pushed along by these waves, gaining more and more and more energy until they reach nearly the speed of light. More than 240 klystrons power SLAC's 2-mile-long linear accelerator.

Particle colliders

A collider brings two beams of particles, each accelerated to nearly the speed of light, into head-on collisions. Scientists sift through the debris from these collisions to find interesting new phenomena.

Large Hadron Collider

The Large Hadron Collider at CERN, the European particle-physics center in Geneva, is by far the world's most powerful particle accelerator. By smashing protons into each other at extremely high energies, scientists expect to create particles never seen before and unlock many secrets, such as the nature of dark matter and why particles (and people) have mass.

Particle physics

Particle physics is the branch of science that studies fundamental particles — the smallest units of matter, such as quarks and electrons — and the forces that govern how they interact. The goal is to understand the ultimate laws of nature, the structure of space and time and the origins of the universe.

Nobel Prizes

Research at SLAC was the basis for three Nobel Prizes in physics that involved fundamental particles. (1) The first proof that protons and neutrons are made of even smaller particles (SLAC's Richard Taylor, with MIT's Jerome Friedman and Henry Kendall, 1990). These turned out to be quarks, which are bound together by other particles called gluons. (2) The discovery of a particle called J/psi, which proved the existence of the charm quark (SLAC's Burton Richter and, independently, MIT's Samuel Ting, 1976). (3) The discovery of the tau lepton, which is a heavier cousin of the electron (SLAC's Martin Perl, 1995).


SLAC's Stanford Synchrotron Radiation Lightsource, or SSRL, produces extremely bright X-rays used to study the world at the atomic and molecular level. These X-rays aid in nearly 30 experimental areas for studies that improve the designs of fuel cells and pharmaceuticals, map the structures of proteins and other molecules, develop new materials and improve the environment.


The Linac Coherent Light Source, or LCLS, at SLAC is the world's most powerful hard X-ray laser. Its brilliant beam — a billion times brighter than previous X-ray sources — arrives in staccato bursts just one-tenth of a trillionth of a second long. With it, scientists can probe materials, molecules, viruses and living cells, freeze the motions of atoms and show chemical bonds breaking and forming.

Free-electron lasers

The term "free-electron laser" refers to the process that generates the laser beam, which gets its power from the fact that the light waves are lined up crest to crest and trough to trough. The LCLS uses part of SLAC's historic 2-mile-long linear accelerator to boost electrons to nearly light speed, then forces them to wiggle through a series of magnets. The electrons give off X-rays, which interact with the electrons to form laser pulses that are incredibly short and intense.