Completion 10: Fermilab Neutrinos from the Main Injector Experiment
Cost: $171 Million

An experiment that will involve hundreds of physicists from 32 universities and research institutes resulted in a project at the Fermi National Accelerator Laboratory in Batavia, Ill.

The experiment seeks to determine whether the neutrino, a shadowy subatomic particle, has mass. Though the existence of the neutrino was postulated in the 1930s and first confirmed in the 1950s, the particle is so light that no measurement has yet been made of its mass.

Previous experiments have revealed three different types of the particle - electron, muon and tau neutrino - and observations from nature suggest that a neutrino of one type sometimes changes into a neutrino of another and back again, a process known as neutrino oscillation. The experiment seeks to confirm the oscillation takes placed to answer whether neutrinos have mass.

The Neutrinos from the Main Injector, or NuMI, experiment might result in developing spin-off knowledge, such as shedding light on fundamental issues about the nature of matter and energy, like the sun and nuclear fusion.

A proton beam will be extracted from the facility's underground main injector and shot into a target of carbon blocks. The collision between the quarks that make up the protons and those that make up the carbon will rain out a variety of particles, such as two-quark states of matter called pi mesons.

These will be focused with cylindrical magnets and dart through a 2,200-ft.-long, 6-ft.-diameter steel pipe lined with concrete. During flight, the anti-down quarks that make up the particles change into anti-up quarks and W particles. W particles, in turn, decay into muons and muon neutrinos.

These particles will shoot through blocks of metal surrounded by concrete to absorb the muons, and the muon neutrinos will zip through a detector made of 200 planes of steel equipped with scintillators to verify the muon-type neutrinos have been produced.
The beam will finally project through 450 mi. of solid earth to Soudan, Minn., where another detector of 484 planes is located and already installed in an abandoned iron mine a half-mile underground.

Underground work

In Illinois two shafts were opened with explosives, including one to service the target area and another the detector area.

A 4,150-ft.-long tunnel was mined and includes space for the two halls, in addition to a chamber between them for the absorber blocks.

Above each shaft, structures were built, the Target building and the Minos - Main Injector Neutrino Oscillation Search - building above the detector area. They will house equipment for the experiment.

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