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 Fermilab 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,” says 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--division scientists released beam in short spurts, or pings, that took a matter of milliseconds to fire.
“We have very good control,” says Fermilab physicist Erik Ramberg. “We can make the beam bursts five milliseconds or three milliseconds or one millisecond.”
Fermilab has used the technique before on beam extracted from the Tevatron. Members of the Accelerator Division began adapting the technique to the Main Injector about a year ago.
When a power outage shut down the Tevatron on Nov. 5, 2008, 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 says. “We proved we could ping the beam out.”
This story first appeared in Fermilab Today.
