Last weekend, at the Aachen RWTH I. Physikalisches Institute in Germany, the permanent magnet has been mounted inside the “flight spare” vacuum chamber. This Neodymium-Iron-Boron alloy cylinder, one meter high per one meter of diameter, has a magnetic field 3,000 times more intense than the magnetic field of Earth and is a veteran of space, since it has been flown in 1998 on the STS91 mission.
Weighting 1.9 tons that become 2.9 tons once the vacuum chamber and the interface structures are added, the permanent magnet is actually a bit lighter than the superconducting one. But, since they have both been designed to host the same silicon tracker, the two magnets have exactly the same internal diameter: this arrangement ensures identical interfaces between the magnet and the other spectrometer subsystems. Inside their vacuum chambers they look like twins.

The two identical vacuum cases built by the NASA JSC team during the integration activities at the beginning of 2009. One is hosting the superconducting magnet and is currently mounted in the AMS experiment, the other now hosts the permanent magnet. When it arrives at CERN, it will undergo the preparation for the swap with its twin, planned during the first half of June.

In few days the permanent magnet will travel to CERN where, in the meanwhile, the AMS team has deintegrated the various detector subsystems. The next month of work will be dedicated to switching the two identical vacuum cases, then the final detector integration will restart to be completed by mid August. By September 1st the experiment will fly from Geneva to Florida, US, destination Kennedy Space Center.