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Posts Tagged ‘particle accelerators’

This article appeared in Fermilab Today on March 30, 2015.

Last week the first SRF cavities of Fermilab's superconducting test accelerator propelled their first electrons. Photo: Reidar Hahn

Last week the first SRF cavities of Fermilab’s superconducting test accelerator propelled their first electrons. Photo: Reidar Hahn

The newest particle accelerators and those of the future will be built with superconducting radio-frequency (SRF) cavities, and institutions around the world are working hard to develop this technology. Fermilab’s advanced superconducting test accelerator was built to take advantage of SRF technology accelerator research and development.

On Friday, after more than seven years of planning and building by scientists and engineers, the accelerator has delivered its first beam.

The Fermilab superconducting test accelerator is a linear accelerator (linac) with three main components: a photoinjector that includes an RF gun coupled to an ultraviolet-laser system, several cryomodules and a beamline. Electron bunches are produced when an ultraviolet pulse generated by the laser hits a cathode located on the back plate of the gun. Acceleration continues through two SRF cavities inside the cryomodules. After exiting the cryomodules, the bunches travel down a beamline, where researchers can assess them.

Each meter-long cavity consists of nine cells made from high-purity niobium. In order to become superconductive, the cavities sit in a vessel filled with superfluid liquid helium at temperatures close to absolute zero.

As RF power pulses through these cavities, it creates an oscillating electric field that runs through the cells. If the charged particles meet the oscillating waves at the right phase, they are pushed forward and propelled down the accelerator.

The major advantage of using superconductors is that the lack of electrical resistance allows virtually all the energy passing through to be used for accelerating particle beams, ultimately creating more efficient accelerators.

The superconducting test accelerator team celebrates first beam in the operations center at NML. Vladimir Shiltsev, left, is pointing to an image of the beam. Photo: Pavel Juarez, AD

The superconducting test accelerator team celebrates first beam in the operations center at NML. Vladimir Shiltsev, left, is pointing to an image of the beam. Photo: Pavel Juarez, AD

“It’s more bang for the buck,” said Elvin Harms, one of the leaders of the commissioning effort.

The superconducting test accelerator’s photoinjector gun first produced electrons in June 2013. In the current run, electrons are being shot through one single-cavity cryomodule, with a second, upgraded model to be installed in the next few months. Future plans call for accelerating the electron beam through an eight-cavity cryomodule, CM2, which was the first to reach the specifications of the proposed International Linear Collider (ILC).

Fermilab is one of the few facilities that provides space for advanced accelerator research and development. These experiments will help set the stage for future superconducting accelerators such as SLAC’s Linac Coherent Light Source II, of which Fermilab is one of several partner laboratories.

“The linac is similar to other accelerators that exist, but the ability to use this type of setup to carry out accelerator science experiments and train students is unique,” said Philippe Piot, a physicist at Fermilab and professor at Northern Illinois University leading one of the first experiments at the test accelerator. A Fermilab team has designed and is beginning to construct the Integrable Optics Test Accelerator ring, a storage ring that will be attached to the superconducting test accelerator in the years to come.

“This cements the fact that Fermilab has been building up the infrastructure for mastering SRF technology,” Harms said. “This is the crown jewel of that: saying that we can build the components, put them together, and now we can accelerate a beam.”

Diana Kwon

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A version of this article appeared in symmetry on April 14, 2014.

From accelerators unexpectedly beneath your feet to a ferret that once cleaned accelerator components, symmetry shares some lesser-known facts about particle accelerators. Image: Sandbox Studio, Chicago

From accelerators unexpectedly beneath your feet to a ferret that once cleaned accelerator components, symmetry shares some lesser-known facts about particle accelerators. Image: Sandbox Studio, Chicago

The Large Hadron Collider at CERN laboratory has made its way into popular culture: Comedian John Stewart jokes about it on The Daily Show, character Sheldon Cooper dreams about it on The Big Bang Theory and fictional villains steal fictional antimatter from it in Angels & Demons.

Despite their uptick in popularity, particle accelerators still have secrets to share. With input from scientists at laboratories and institutions worldwide, symmetry has compiled a list of 10 things you might not know about particle accelerators.

There are more than 30,000 accelerators in operation around the world.

Accelerators are all over the place, doing a variety of jobs. They may be best known for their role in particle physics research, but their other talents include: creating tumor-destroying beams to fight cancer; killing bacteria to prevent food-borne illnesses; developing better materials to produce more effective diapers and shrink wrap; and helping scientists improve fuel injection to make more efficient vehicles.

One of the longest modern buildings in the world was built for a particle accelerator.

Linear accelerators, or linacs for short, are designed to hurl a beam of particles in a straight line. In general, the longer the linac, the more powerful the particle punch. The linear accelerator at SLAC National Accelerator Laboratory, near San Francisco, is the largest on the planet.

SLAC’s klystron gallery, a building that houses components that power the accelerator, sits atop the accelerator. It’s one of the world’s longest modern buildings. Overall, it’s a little less than 2 miles long, a feature that prompts laboratory employees to hold an annual footrace around its perimeter.

Particle accelerators are the closest things we have to time machines, according to Stephen Hawking.

In 2010, physicist Stephen Hawking wrote an article for the UK paper the Daily Mail explaining how it might be possible to travel through time. We would just need a particle accelerator large enough to accelerate humans the way we accelerate particles, he said.

A person-accelerator with the capabilities of the Large Hadron Collider would move its passengers at close to the speed of light. Because of the effects of special relativity, a period of time that would appear to someone outside the machine to last several years would seem to the accelerating passengers to last only a few days. By the time they stepped off the LHC ride, they would be younger than the rest of us.

Hawking wasn’t actually proposing we try to build such a machine. But he was pointing out a way that time travel already happens today. For example, particles called pi mesons are normally short-lived; they disintegrate after mere millionths of a second. But when they are accelerated to nearly the speed of light, their lifetimes expand dramatically. It seems that these particles are traveling in time, or at least experiencing time more slowly relative to other particles.

The highest temperature recorded by a manmade device was achieved in a particle accelerator.

In 2012, Brookhaven National Laboratory’s Relativistic Heavy Ion Collider achieved a Guinness World Record for producing the world’s hottest manmade temperature, a blazing 7.2 trillion degrees Fahrenheit. But the Long Island-based lab did more than heat things up. It created a small amount of quark-gluon plasma, a state of matter thought to have dominated the universe’s earliest moments. This plasma is so hot that it causes elementary particles called quarks, which generally exist in nature only bound to other quarks, to break apart from one another.

Scientists at CERN have since also created quark-gluon plasma, at an even higher temperature, in the Large Hadron Collider.

The inside of the Large Hadron Collider is colder than outer space.

In order to conduct electricity without resistance, the Large Hadron Collider’s electromagnets are cooled down to cryogenic temperatures. The LHC is the largest cryogenic system in the world, and it operates at a frosty minus 456.3 degrees Fahrenheit. It is one of the coldest places on Earth, and it’s even a few degrees colder than outer space, which tends to rest at about minus 454.9 degrees Fahrenheit.

Nature produces particle accelerators much more powerful than anything made on Earth.

We can build some pretty impressive particle accelerators on Earth, but when it comes to achieving high energies, we’ve got nothing on particle accelerators that exist naturally in space.

The most energetic cosmic ray ever observed was a proton accelerated to an energy of 300 million trillion electronvolts. No known source within our galaxy is powerful enough to have caused such an acceleration. Even the shockwave from the explosion of a star, which can send particles flying much more forcefully than a manmade accelerator, doesn’t quite have enough oomph. Scientists are still investigating the source of such ultra-high-energy cosmic rays.

Particle accelerators don’t just accelerate particles; they also make them more massive.

As Einstein predicted in his theory of relativity, no particle that has mass can travel as fast as the speed of light—about 186,000 miles per second. No matter how much energy one adds to an object with mass, its speed cannot reach that limit.

In modern accelerators, particles are sped up to very nearly the speed of light. For example, the main injector at Fermi National Accelerator Laboratory accelerates protons to 0.99997 times the speed of light. As the speed of a particle gets closer and closer to the speed of light, an accelerator gives more and more of its boost to the particle’s kinetic energy.

Since, as Einstein told us, an object’s energy is equal to its mass times the speed of light squared (E=mc2), adding energy is, in effect, also increasing the particles’ mass. Said another way: Where there is more “E,” there must be more “m.” As an object with mass approaches, but never reaches, the speed of light, its effective mass gets larger and larger.

The diameter of the first circular accelerator was shorter than 5 inches; the diameter of the Large Hadron Collider is more than 5 miles.

In 1930, inspired by the ideas of Norwegian engineer Rolf Widerøe, 27-year-old physicist Ernest Lawrence created the first circular particle accelerator at the University of California, Berkeley, with graduate student M. Stanley Livingston. It accelerated hydrogen ions up to energies of 80,000 electronvolts within a chamber less than 5 inches across.

In 1931, Lawrence and Livingston set to work on an 11-inch accelerator. The machine managed to accelerate protons to just over 1 million electronvolts, a fact that Livingston reported to Lawrence by telegram with the added comment, “Whoopee!” Lawrence went on to build even larger accelerators—and to found Lawrence Berkeley and Lawrence Livermore laboratories.

Particle accelerators have come a long way since then, creating brighter beams of particles with greater energies than previously imagined possible. The Large Hadron Collider at CERN is more than 5 miles in diameter (17 miles in circumference). After this year’s upgrades, the LHC will be able to accelerate protons to 6.5 trillion electronvolts.

In the 1970s, scientists at Fermi National Accelerator Laboratory employed a ferret named Felicia to clean accelerator parts.

From 1971 until 1999, Fermilab’s Meson Laboratory was a key part of high-energy physics experiments at the laboratory. To learn more about the forces that hold our universe together, scientists there studied subatomic particles called mesons and protons. Operators would send beams of particles from an accelerator to the Meson Lab via a miles-long underground beam line.

To ensure hundreds of feet of vacuum piping were clear of debris before connecting them and turning on the particle beam, the laboratory enlisted the help of one Felicia the ferret.

Ferrets have an affinity for burrowing and clambering through holes, making them the perfect species for this job. Felicia’s task was to pull a rag dipped in cleaning solution on a string through long sections of pipe.

Although Felicia’s work was eventually taken over by a specially designed robot, she played a unique and vital role in the construction process—and in return asked only for a steady diet of chicken livers, fish heads and hamburger meat.

Particle accelerators show up in unlikely places.

Scientists tend to construct large particle accelerators underground. This protects them from being bumped and destabilized, but can also make them a little harder to find.

For example, motorists driving down Interstate 280 in northern California may not notice it, but the main accelerator at SLAC National Accelerator Laboratory runs underground just beneath their wheels.

Residents in villages in the Swiss-French countryside live atop the highest-energy particle collider in the world, the Large Hadron Collider.

And for decades, teams at Cornell University have played soccer, football and lacrosse on Robison Alumni Fields 40 feet above the Cornell Electron Storage Ring, or CESR. Scientists use the circular particle accelerator to study compact particle beams and to produce X-ray light for experiments in biology, materials science and physics.

Sarah Witman

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