In a ceremony on Monday morning, September 15, officials at the Department of Energy’s Fermi National Accelerator Laboratory will mark the end of one era in frontier particle physics research at the laboratory and the beginning of another. At the event, to be held at 9:15 a.m. in Fermilab’s accelerator control room, officials plan to flip the switch that turns off forever the beam of protons in Fermilab’s historic Main Ring, the Laboratory’s original particle accelerator.
For 25 years, physicists have used the accelerator for experiments that helped to create our current picture of the ultimate structure of matter, the Standard Model of particle interactions.
Later on the same day, Fermilab staff will begin the process of dismantling the Main Ring and transplanting its quadrupole, or focusing, magnets to serve as components of the Laboratory’s newest accelerator, the Main Injector. When the Main Injector begins operating in 1999, scientists expect it will result in a tenfold increase in the number of high-energy proton-antiproton collisions at Fermilab’s Tevatron, the world’s highest-energy particle accelerator.
Physicists will use the new, high-luminosity Tevatron beams to explore the frontiers of particle physics, probing for evidence of phenomena beyond the familiar framework of the Standard Model.
Physicist Robert Wilson, Fermilab’s founding director, broke ground for the Main Ring on October 3, 1969. The first beam of 200-billion-electron-volt protons circled its four-mile circumference in 1972, and the Main Ring reached its operating energy of 400 billion electron volts later that year. In 1977, physicist Leon Lederman used the accelerator’s particle beams in experiments that revealed the bottom quark, the first quark of the third generation of elementary particles that are nature’s ultimate building blocks.
Since 1983, the Main Ring has served as an injector to the Tevatron, where in 1995, physicists discovered the bottom quark’s partner, the top quark, in collisions between protons and antiprotons, their antimatter counterparts. As an injector, however, the Main Ring constituted a kind of bottleneck for antiproton beams, limiting the rate of high-energy particle collisions. Because the particular collisions that are of interest to physicists are extremely rare — only a handful of the trillions created — increasing the total number of collisions leads to a corresponding increase in physics productivity.
Consequently, accelerator physicists designed the $229 million Main Injector as a replacement for the Main Ring.
“For twenty-five years, the Main Ring has been an essential part of our scientific program,” said Fermilab Director John Peoples. “For the first eleven years, it was the forefront machine in particle physics, the tool with which we discovered the first quark of the third generation. For the past fourteen years, it has been an excellent injector and source of protons for making antiprotons.
“We now have a better way to carry out the Main Ring’s functions,” Peoples said. “The succession of accelerators, one replacing another, is a tradition in the Cornell-Fermilab genealogy of particle accelerators begun nearly fifty years ago by Bob Wilson. Now it is time to say farewell to the Main Ring. It is a moment to celebrate the Main Ring’s past, and to prepare for the future.”
Many Fermilab employees who took part in building, commissioning and operating the Main Ring will be on hand to bid it farewell. Among them is Accelerator Operations Chief Bob Mau.
“I sure hope it will be easier to turn it off than it was to turn it on,” Mau said.
Fermilab is operated by Universities Research Association, Inc. under contract with the Department of Energy.