Preventing corrosion in subatomic environments

Citation

(2001), "Preventing corrosion in subatomic environments", Anti-Corrosion Methods and Materials, Vol. 48 No. 6. https://doi.org/10.1108/acmm.2001.12848fab.013

Preventing corrosion in subatomic environments

Preventing corrosion in subatomic environments

Keywords: Universal Metal Finishing, Corrosion prevention

A 650lb prototype horn is being used for focusing neutrinos that prevents corrosion which would otherwise cause loss of subatomic particles called pions.

The anodising process is called Metalast. Used by Universal Metal Finishing (UMF) Co., of Chicago, USA, it acts as a dielectric insulator and also resists degradation from radiation. This is important because the horns will eventually become radioactive during the course of the experiment in which they serve.

UMF selected a 1.8 to 2.3-milthick sulphuric acid hardcoat followed by a mid temperature nickel seal as the coating of choice. UMF says thinner coatings did not perform well and were prone to pitting. Porosity made thicker oxide coatings poor performers as well.

The Metalast process uses a special pulsing technique during anodising. A computer controls ramp-up, voltage, and electrical current to help avoid the tendency of anodised parts to burn. If the oxide-build and electrical pulse are not in sync the parts will be attacked by the acid in the bath.

Metalast is said to give a consistent coating with a tighter, denser pore structure that is more elastic. The elasticity helps the surface resist cracking and crazing. Metalast is also said to be less prone to "edge effects" – the oxide does not fracture at the corner of the part.

The anodised focusing horns will help resolve a conundrum: if 90 per cent of matter is not composed of the smallest particles already identified to date (quarks and leptons) then what is it? Researchers hope to prove that the unidentified matter consists of elementary particles called neutrinos. Neutrinos have no charge, travel at the speed of light, and can pass through anything.

They also seem to have no mass. According to Dr David Ayres, Fermilab, Chicago, the answer may come if the Main Injector Neutrino Oscillation Search (Minos) experiment can observe neutrino oscillation. Basic physics stipulates that if something oscillates then it must have mass. Theoretically, neutrinos could have mass.

Key to the experiment are two anodised focusing horns. Researchers at Fermilab will first extract and bend protons from their accelerator's main injector onto a graphite target. At point of impact, elementary particles called pions will be produced, spraying in all directions from the graphite target. Here the first focusing horn will collect and direct the pions into a column or beam. Some distance away, the pions go through a second horn for further refinement.

Once focused, they enter a 650-m long pipe where they form into neutrinos. To observe if these neutrinos do in fact oscillate scientists will send them on a 735 kilometer journey through an aquifer. Detectors at each end of the route will characterise the neutrinos and look for any sign of oscillation.

The success of the project relies on the alignment accuracy of the beam. Once the pions decay, the neutrinos can no longer be steered, it is imperative for the pion beam to be precisely on target. The focusing horns target the direction of the beam via a magnetic field. They are made from fairly conductive 6061 aluminium. Any corrosion of the horns will cause pion loss and ultimately may result in failure of the experiment.

Combating corrosion on the horns is a major challenge. The Hornes inner conductors are subjected to 200-kA pulses every 5 msec to generate the magnetic field.