• Assistant Operations Group Leader Larry O'Brien (right) and Chief Operator Larry Longcoy tune the electron linear accelerator from the Bates central control room. Recent upgrades to the accelerator radio frequency system have made it possible to produce a beam of electrons at an energy of one billion electron volts.

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Accelerator achieves 1 billion electron volts

The Bates Linear Accelerator delivered a beam at an energy of one billion electron volts on February 14. The achievement, which marks a milestone for the laboratory that will have important consequences for the scientific program, is the result of a sustained and systematic upgrade program of the radio frequency systems for the accelerator.

"It's worth noting that other beam parameters were not compromised in achieving the one billion electron volts of beam energy," said Dr. Kenneth D. Jacobs, accelerator systems division head at Bates. "The electron beam current and pulse repetition rate were maintained at values needed to run future physics experiments. We have been working towards this goal for a number of years."

The Bates accelerator is used for basic research in medium-energy nuclear physics. The facility consists of a linear accelerator 160 meters long, which delivers an electron beam to the 190-meter circumference South Hall Ring. The South Hall Ring can be used to deliver a high duty factor extracted beam to an external target, or operated in storage mode where the linear accelerator beam is repeatedly stacked to obtain a high circulating current.

The performance demonstrated indicates that Bates can deliver an extracted beam to experiments up to 1 billion electron volts and store the beam in the SHR up to about 1.1 billion electron volts. The stored beam will be used with the Bates Large Acceptance Spectrometer Toroid (BLAST) to carry out experiments with polarized internal gas targets. BLAST is scheduled to begin commissioning next year and had been counting on 0.9 billion electron volts.

"The energy increase means an increase in count rate for the BLAST experiments and hence higher quality experimental data. This opens up the possibility of new physics," said Professor of Physics Richard Milner, Bates director.

The MIT Bates Linear Accelerator is operated by MIT for the Department of Energy as a national user facility. More than 200 physicists from 52 institutions are currently involved in active experiments at Bates.

A version of this article appeared in MIT Tech Talk on March 1, 2000.

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