Homegrown Particle Accelerators

More is more – nowhere is that truer than at the world’s most powerful atom smasher, the Large Hadron Collider in Switzerland, where scientists last week concluded a six-month series of experiments where they forced infinitesimally tiny particles to smash against each other at double the energy level ever recorded.

The higher energy level – 13 trillion electronvolts – will increase physicists’ chances of answering some of the most daunting questions in science. Through their work, researchers hope to find out if there are extra dimensions in the universe other than the three we’re familiar with. They also hope to elucidate what dark matter might be – that’s the “stuff” that makes up about a quarter of the universe.

And there might even be surprises along the way, said physicist Michael Barnett, of the Lawrence Berkeley National Laboratory.

“We don’t know what we don’t know,” said Barnett, who recently spent a week at the Large Hadron Collider, in Geneva. “All we do is collide protons.”

The collider smashes tiny constituents of matter called protons against other protons inside a 17-mile ring so long that it straddles the border of Switzerland and France.

The giant accelerator’s first run started in 2010 and culminated two years later with the discovery of the Higgs boson, also known as the “God particle” because it has the god-like ability to confer mass to other particles. Scientists like Barnett hope that it will take two more years to find clues about extra dimensions and dark matter.

The process involves looking for phenomena that can only be created inside a particle accelerator, such as microscopic black holes that disappear in less than a millionth of a second, leaving only traces to be pored over by scientists.

“It’s like fireworks,” said Barnett, “with tails that become more and more elaborate.”

Many of the technologies that made the Large Hadron Collider possible were pioneered in the Bay Area.

Physicists on the University of California, Berkeley, campus in the 1930s and at the Stanford Linear Accelerator Center, in Menlo Park, in the 1970s, created precursors to the Large Hadron Collider that led to key discoveries about the tiny constituents of the atom – from the nucleus all the way down to quarks.

In its first iteration, the cyclotron created by UC Berkeley physicist Ernest Lawrence in 1930 fit in the palm of his hand. It was a breakthrough because, without requiring much energy, it could produce very energetic particles in a small space. This allowed physicists to readily investigate the atom’s nucleus by creating elements with large nuclei.

The resulting new field of nuclear science has a complicated legacy, said Lawrence Berkeley Lab nuclear physicist Larry Phair. Nuclear physics were used to build the atomic bomb, as well as to create the medical accelerators that are now commonly used to fight cancer.

Subsequent versions of the cyclotron were so big that they were housed in their own buildings. The Lawrence Berkeley Lab started out as the facility that Ernest Lawrence built above the UC Berkeley campus to house his ever-bigger cyclotrons.

When it opened in Menlo Park in 1966, the Stanford Linear Accelerator Center, now the SLAC National Accelerator Laboratory, was the longest particle accelerator in the world. The linear accelerator sent electron beams traveling down a two-mile row of microwave-oven-like devices and smashed them against a stationary target. Physicists used these accelerated electrons to investigate what was inside the protons and neutrons, and in 1968 they found that they were made up of minuscule constituents they called quarks.

A few years later, SLAC physicist Burton Richter built a collider – a type of particle accelerator in which particle beams are smashed against each other to reach high energy levels.

“All the energy of those two beams could get transformed into new kinds of particles,” said Richter.

The so-called SPEAR collider that Richter built led him and his team to discover a more massive quark called the charm quark, and won him the Nobel Prize in physics.

“It was a revolutionary idea, to collide two beams against each other,” said Barnett. The SPEAR collider became a precursor to the Large Hadron Collider.

Today, dozens of physicists and graduate students at the Lawrence Berkeley Lab and SLAC are working at the Large Hadron Collider, making regular trips to Geneva and crunching data back home in their labs.

The particle accelerators at both facilities have been given new uses.

The cyclotron at the Lawrence Berkeley Lab is used to test computer chips that go into satellites, by exposing them to high-radiation conditions similar to those they’ll encounter in space.

And the X-rays emitted by accelerated particles at SLAC are being used to study the impact of climate change on coral reefs.

For Richter, the Large Hadron Collider offers the tantalizing possibility of answering fundamental questions about the universe, one by one.

“The blackboard is covered with Post-it notes now,” said Richter.

He looks forward to “going down the line and removing them all.”