A Flight Simulator for the World's Smallest Beam

Mar 31, 2009
The Accelerator Test Facility 2 in Japan uses a 50-meter series of magnets to focus its electron beam. (Photo by N. Toge, KEK.)

(PhysOrg.com) -- Commissioning has begun at the Japan-based Accelerator Test Facility 2, a major technology test bed for future accelerators, including the proposed International Linear Collider, or ILC. During the two-year commissioning process, SLAC National Accelerator Laboratory physicists are shuttling back and forth to KEK, the high-energy accelerator lab in Tsukuba, to join an international team of scientists working around the clock to get the accelerator's final focus system up and running. When fully commissioned, this system will squeeze the facility's electron beam down to a slender ribbon just 35 nanometers thick—the narrowest beam of particles ever achieved.

"We're making the world's smallest beam," said SLAC physicist Mark Woodley, who returned from a visit to Japan in early March. The tiny beam will be essential for the ILC, the next large scale high-energy particle collider planned by the international community, after the . "If you can pack more electrons and into a smaller space, they're more likely to collide, so you'll get more events."

At the test facility in Japan, a racetrack 139 meters in circumference delivers a beam of electrons to the final focus system, a 50-meter series of magnets. Since construction of the ATF2 began in 2007, SLAC has built and delivered several key parts, including power supplies, magnet movers, a new type of beam position monitor, and the final two quadrupole magnets. Now it's a matter of getting every component of the final focus system to work in concert to focus the beam to less than a thousandth of the width of a human hair—and keep it there.

"It's like a system of lenses," Woodley said. "There are aberrations, interplay between effects."

"Even natural movements of the ground affect it," said accelerator physicist Glen White, who returned from his most recent round in Japan in mid-March. "The beam drifts in seconds to minutes."

An essential part of the ATF2 is its system of diagnostics—ingenious devices that measure the beam's size and position. The first challenge in commissioning is calibrating these devices so that they take accurate measurements. A software program White developed is helping enormously in this process.

Dubbed the "flight simulator," the program is a virtual version of the test facility. It takes into account everything that affects the beam—magnetic field strength, temperature, even distant tremors in the Pacific plate—and generates a picture of what the beam should look like. White created it so that collaborators could improve their understanding of the ATF2 beam by playing with the parameters of a virtual beam.

On his last trip to KEK, White, with the help of Woodley and a team of collaborators, worked on adapting the program to read data from all of the ATF2's magnets and diagnostic electronics. This lets ATF physicists tweak the magnets, compare the diagnostic readouts to the software's calculated beam, and calibrate accordingly.

Achieving such a narrow beam is like balancing something on the head of a pin; tiny changes in magnet position or magnetic field strength can wreak havoc. So physicists are using the software to develop tuning algorithms, a sequence of adjustments—in magnet position, for instance, or in magnetic field strength—that produce a thinner beam.

"It's like a television, except you have maybe 20 knobs you can turn—brightness, contrast, color, etc.," White explained. "You're trying to tweak all of these things just right to get a clear picture, but at the same time there's somebody underneath, working against you."

These tuning algorithms will help transform the "flight simulator" into a sort of "autopilot" that would constantly read information about the beam and retune accordingly.

"When you're running the beam, you want something to take care of all this for you, so you can just sit and watch the beam," White said.

Although inspired by the needs of the ILC, the technical achievements of the ATF2 facility will be applicable to other designs, such as CERN's proposed Compact Linear Collider. Of even broader importance are the next generation of physicists who will leave the training ground of the ATF2 with the skills and knowledge to build the accelerators of the future, said SLAC physicist Andrei Seryi, deputy to the ATF spokesperson, responsible for the ATF2 project.

"This is a place where young people can learn accelerator physics and continue in other projects," he said.

Provided by SLAC

Explore further: New filter could advance terahertz data transmission

add to favorites email to friend print save as pdf

Related Stories

LCLS Beam Already in Action

Aug 06, 2007

The Near and Far Experimental halls are still under construction, but already scientists are putting the Linac Coherent Light Source (LCLS) beam to use. The LCLS electron beam, first generated in April, is ...

A Positive Spin

Feb 22, 2006

Beams with polarized particles greatly boost the physics output of high energy physics colliders. While it has been straightforward to make polarized electron beams, polarizing positrons is more difficult, ...

Clearing Electron Clouds

Aug 02, 2007

Clouds might be welcome during a drought, but you definitely don't want them in your beam pipes. Researchers around the world are working out how to keep a section of the proposed International Linear Collider—the ...

Groovy Project Solving Cloudy Problem

Sep 07, 2007

Experiments in the PEP-II accelerator have shown that beam pipes with grooves can snare unwelcome electrons, greatly reducing the formation of electron clouds that can disturb the beam.

Recommended for you

Breakthrough in OLED technology

11 hours ago

Organic light emitting diodes (OLEDs), which are made from carbon-containing materials, have the potential to revolutionize future display technologies, making low-power displays so thin they'll wrap or fold ...

Throwing light on a mysterious human 'superpower'

14 hours ago

Most people, at some point in their lives, have dreamt of being able to fly like Superman or develop superhuman strength like the Hulk. But very few know that we human beings have a "superpower" of our own, ...

New filter could advance terahertz data transmission

Feb 27, 2015

University of Utah engineers have discovered a new approach for designing filters capable of separating different frequencies in the terahertz spectrum, the next generation of communications bandwidth that ...

The super-resolution revolution

Feb 27, 2015

Cambridge scientists are part of a resolution revolution. Building powerful instruments that shatter the physical limits of optical microscopy, they are beginning to watch molecular processes as they happen, ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.