Graphite Metallizing Corp. (USA) said its Graphalloy bearings have been put to use by Fermilab, solving an ongoing problem with the focusing system for subatomic particles.

Fermilab is the U.S. Department of Energy's Fermi National Accelerator Laboratory, near Chicago in Batavia, Illinois. The lab focuses its research efforts on the physics of subatomic particles -- in this case, neutrinos [about neutrinos] [and more].

Fermilab's Main Injector Neutrino Oscillation Search (MINOS) project [website] is a, "long baseline neutrino experiment designed to observe the phenomena of neutrino oscillations, an effect which is related to neutrino mass."

MINOS and a number of other neutrino oscillation detection experiments are being done to determine if neutrinos have mass -- and if so, what it is. Currently, physicists believe that detecting neutrino oscillation is a promising way to answer that question beyond calculations suggesting 0-15eV. Physicists and cosmologists also believe that understanding neutrinos is the key to understanding a universe of dark matter, supernovas, and even the sun's mechanisms.

The MINOS project involves generating and detecting neutrinos at Fermilab, while focusing them into a beam. That focused beam of neutrinos is aimed a half-mile down and 450 miles away at detectors in the Soudan Underground Mine State Park in northern Minnesota.

Neutrinos populating the beam are created by the NuMI (Neutrinos at the Main Injector) Beamline facility at Fermilab. NuMI focuses a 120 GeV/c proton beam on a graphite target. The collisions create charged mesons ( pions[π] and kaons[K]). The π (and perhaps some K) decay into muons and muon neutrinos. 8,000 tons of steel and earth structures surround the decay pipe to absorb the undecayed hadrons and muons.

After traveling 450 miles (neutrinos interact very little with their surroundings, so the stream arrives intact), the neutrino stream is examined for oscillations into electron neutrinos.

The beam focusing is done by two "horns" or "lenses" which are 3-meter-long decay tubes with a parabolic interior cross-section. The focusing horns are pulsed at 17kW/200kA to produce intense torroidal magnetic fields, topping out at 3 Tesla at 200kA and 9000 psi.

Because the detectors are desensitized to reject low-energy atmospheric "natural background" neutrinos, the neutrinos created by Fermilab must have energy in the range of order 1 to 16 GeV for the detectors to "see" them.

In addition, these horns must not only be located with extreme precision to focus the particle stream on a point 450 miles away, but also be able to change position for different conditions, experiments, and servicing.

These focusing horns ride in high-precision bearings with unique specifications for the environment. The bearings cannot be any plastic or polymer, organic, or metal bushing, or lubricant. The highly radioactive atmosphere, extreme heat, and corrosive atmosphere (a high-humidity atmosphere with pH of only 2.6) causes rapid failure and hydrogen embrittlement. And NuMI Beamline bearing failures are "not acceptable." Ignoring the potential dangers and collateral damage from severe misalignment, replacing a focusing horn bearing requires up to 14 days of dangerous, highly automated and technically difficult service.

After other materials, Fermilab has now settled on Graphalloy bearings for the focusing horn application.

In a release, Graphite Metallizing said: "This is an excellent example of how Graphalloy problems under harsh operating conditions."

Graphalloy bearings are self-lubricating graphite/metal alloy, with wide operating parameters including a temperature range of -400°F to +1000°F.

a recent Fermilab NuMI presentation