Historical Content Note: The following material is reprinted from publications from throughout Fermilab's history. It should be read in its original historical context.

High Hopes, Tight Quarters

Unique Recycler, world’s largest array of permanent magnets, taking shape in crowded Main Injector tunnel.

The magnets are numbered in the hundreds; their weight is measured in tons. The available space in the tunnel is usually about four and a half feet, but it can be as little as two or three inches, and the forklifts doing the moving have been custom designed for these tight quarters.

The obstacles include water systems, cable trays, workers performing other installations, and the precisely aligned components of the signature Main Injector accelerator.

The consequences of a possible slip-up: Don’t even ask.

Installation crews can put eight to 10 magnets in place in a day, if the magnets are located close together. Installing a magnet means lifting it from the floor level with the forklift, raising it to a level above the Main Injector magnets, fitting it between pipes for the low conductivity water system and cable trays suspended from the ceiling, moving the magnet horizontally to fit it onto the magnet stands, then moving out the forklift—being careful to avoid even slightly bumping the Main Injector magnet.

"This is a delicate operation and it requires some finesse," said Cons Gattuso of the Main Injector Department. "Even given the range of technical challenges we face in installation, safety is always our highest priority."

Gattuso, one of the careful overseers of the installation of the Recycler, is also the Operations Specialist for the machine that’s the only one of its kind, anywhere.

When Run II of the Tevatron gets underway, the 1.99-mile circumference Recycler will act as a storage ring for antiprotons. But it will also do something no other accelerator has done before: it will salvage leftover antiprotons, literally "recycling" them for future use, thus saving time and energy in the production of the rare particles that occur only 15 times in a million proton collisions at the antiproton production target.

The Recycler is taking shape, with about 85 percent of its permanent gradient magnets installed (291 of 344); the beam tube that will house the streams of antiprotons currently extends approximately halfway around the ring. Gradient magnets combine the duties of quadrupole magnets, which focus the particle beam, and dipole magnets, which steer the beam around the circuit.

The Recycler's dependence on permanent magnets, instead of the electromagnets that are the usual equipment for particle accelerators, is an extension of the technology employed so successfully on the new 8-GeV line, which transfers protons between the Booster and the Main Injector. But the permanent magnets used in the Recycler represent the next generation of development, with different standards of performance that translate into a need for greater precision.

"The 8-GeV line told us that our design for the gradient magnets works in the real world," Gattuso said. "But our concerns with the Recycler, where particles will be making multiple passes through the magnetic fields, are different from the 8-GeV line, where particles make a single pass through a transfer line."

When fully operating, the Recycler might be storing a particle beam for up to a week. Since the beam will complete about 100,000 revolutions per second, that means a staggering number of repeated trips past each magnet—and a staggering number of opportunities for error, requiring painstaking precision.

"Any error created because of a misaligned magnet gets multiplied every time the beam comes past that magnet," Gattuso said. "We would wind up losing beam over time. The design of these permanent magnets is similar (to the 8-GeV line), but the tolerances must be much tighter."

Gattuso said those responsible for the installation of the Recycler, coordinated through Main Injector Department Head Phil Martin, sometimes arrive before dawn and leave well into the night.

"It’s a real hive of activity down there, with a lot of things going on at once,” Gattuso said. “We installed our first magnet stand in the first week of February, and I feel as if we’ve done a lot of good work since then."