Accelerator physicists show future collider compatibility

As fractions of the beam are extracted in short bursts, or pings, the amount of current in the Main Injector extraction magnet, represented by the green line, spikes while the amount of beam in the Main Injector, represented by the red line, drops.

By temporarily altering the way the Main Injector releases beam, the Accelerator Division has shown that physicists can use it to test machinery built for future accelerators.

The recently demonstrated mode of transferring beam out of the Main Injector imitates the way future colliders, such as the International Linear Collider, would function.

"We can provide users with beam that has the characteristics they want," said Fermilab engineer Peter Prieto, who helped reconfigure the Main Injector slow extraction regulator.

Rather than releasing beam in one of the usual methods - all at once or draining in a slow spill over a period of one to four seconds - AD released beam in short spurts, or pings, that took a matter of milliseconds to fire.

"We have very good control," said Fermilab physicist Erik Ramberg. "We can make the beam bursts five milliseconds or three milliseconds or one millisecond."

When a power outage shut down the Tevatron on Nov. 5, they took the opportunity to test the ping method without the risk of interfering with the Tevatron's operation. They announced the results at the Linear Collider Workshop last month.

To release the beam in pings, Fermilab operators needed to adjust the tune of the machine. When proton beams circulate around the Main Injector, they oscillate in waves. The height of those waves is determined by the magnets in the Main Injector.

When operators want just a portion of the protons to exit the Main Injector, they change the tune of the injector so that some of the protons will waver enough to be directed out of the ring. To kick out beam in bursts, engineers added carefully measured jolts of energy to the magnets at specific intervals.

Operators hope to continue perfecting the technique before attempting to use it while the Tevatron is running.

"This was proof of a principle," Prieto said. "We proved we could ping the beam out."

-- Kathryn Grim

Physicists hot for ultracold

From Science News
December 2008

A laser's light tickle tricks molecules into sitting still

Molecules are hot. They zip, spin and vibrate with frenetic motion. They jiggle and twist on the inside and bounce on the outside, imparting structure and physical properties to nearly everything that exists. But by achieving temperatures colder than any in the natural world, physicists can almost stop these speed demons cold.

Like surgeons who slow a beating heart by packing ice around a patient's chest, physicists have recently coaxed molecules into ultracold states in which motion is nearly gone. Researchers are left with intriguing, exquisitely controllable new specimens to poke and prod, enabling experiments that would be impossible with everyday hot molecules that rotate and vibrate at their usual frenzied pace.

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