A Key Contribution from Brookhaven Laboratory

The heart of the Muon g-2 experiment is the 50-foot-diameter muon storage ring, originally used in an earlier experiment at Brookhaven National Laboratory.

The ring

Physicists plan to measure the muon g-2 very precisely at Fermilab, surpassing the precision of a g-2 measurement previously made at Brookhaven National Laboratory. A major planned improvement over the previous experiment is to use a more intense and pure beam of muons made possible at Fermilab. At the heart of the device that stores these beams is a set of three 50-foot-diameter superconducting coils that energize the 700-ton storage ring magnet. Similar to those in a medical MRI machine, the coils are made of titanium-niobium filaments in a copper matrix surrounded by ultra-pure aluminum. Together, they produce a field of 1.45 Tesla, approximately 30,000 times the Earth's magnetic field. The magnet was shimmed to produce a uniform field that was constant to a few parts per million and was measured to better than 1 part in 10 million, the best ever for its size. For this reason, the experiment plans to reuse Brookhaven's superconducting electromagnet.

Transporting the storage ring to Fermilab

The experiment's finely crafted storage ring is sometimes referred to as a "700-ton Swiss watch" because of its high precision and enormous weight. The experiment at Fermilab will reuse this magnet to store a more intense muon beam than the one used at Brookhaven, producing 20 times more data and improving the precision of the g-2 measurement by a factor of four.

Transporting the g-2 ring 900 miles from Brookhaven to Fermilab will be a feat of a different sort. While the iron that makes up the magnet yoke comes apart, the three 50-foot-diameter superconducting coils that energize the magnet do not, and must therefore travel as a single unit.

In order to maintain the superb accuracy of the electromagnet, the 50-foot-diameter circular coil shape must be maintained to within a quarter-inch, and flatness to within a tenth of an inch, during transportation. The land route would use four-lane highways and local roads (two lanes each way) to minimize obstructions from traffic signs and vegetation, with minimal disruption to public utilities such as electrical or telephone. Land transportation will occur around midnight on a weekend to minimize disruption to regular traffic. The truck will move about 5 miles per hour with escort from police and other technical experts to ensure safety to the public and mechanical integrity of the coils.

Once the truck arrives at Fermilab, the ring will be moved into the laboratory's MC1 Building through a special slot in the wall of the building.