Giant magnet ring makes epic journey

19 July 2013

Muon g-2 is a new experiment to measure the anomalous magnetic moment of the muon – in other words, the difference of the value of its magnetic moment g from the simplest expectation of 2. However, before the experiment begins, its centrepiece – a complex electromagnet spanning more than 15 m in diameter – had to embark on a long, careful journey from Brookhaven National Laboratory (BNL) in New York to Fermilab in Illinois.

The magnet ring was built at Brookhaven in the 1990s for the E821 experiment, which ran there from 1997 until 2001. Its measurement of g-2 is still one of the few hints for new physics beyond the Standard Model. Constructed of aluminium and steel with superconducting coils inside, the magnet cannot be taken apart or twisted more than a few millimetres without irreparably damaging the coils. As a result, the Muon g-2 team devised a plan for a five-week journey of 5150 km over land and sea.

The journey began when the ring left Brookhaven on 22 June. It was loaded onto a specially prepared barge to be taken down the East Coast of the US, around the tip of Florida and up a series of rivers to Illinois. The ring was then attached to a truck built specially for the move and driven to Fermilab to arrive there in late July.

• For more information about Muon g-2, see

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