File:Alpha 1 racetrack, Uranium 235 electromagnetic separation plant, Manhattan Project, Y-12 Oak Ridge.jpg

English: Large electromagnet called "Alpha 1 racetrack" used to separate the isotope uranium-235 from uranium-238 in natural uranium at the Y-12 plant in Oak Ridge, Tennessee, around 1945, part of the secret US World War 2 Manhattan Project to make an atomic bomb. It is divided into sections called alpha calutrons which operate on the principle of the mass spectrometer. In a large vacuum tank the magnetic field bends the path of lighter ²³⁵U ions in a beam of uranium ions more than the heavier ²³⁸U ions, so the two isotopes separate into separate beams and are collected by separate cups. The calutron tanks are spaced around the ring, located between the coils that generate the magnetic field. Since copper was desperately scarce during World War 2, the magnet's coils were made of thousands of tons of silver, borrowed from the U.S. Treasury. Eventually 14,700 tons were used for coil windings, returned to the Treasury after the war. The rectangular duct around the top of the machine contains the silver bussbar that supplies the current. This technique is no longer used for uranium enrichment.

Caption: "View inside an Alpha 1 building, looking over one track toward the second. The view shows inside and outside tank fronts with enclosed bus running along the top of the tracks. Spare "tank units" may be seen on the floor between the tracks"