Technological support for AMS (Alpha Magnetic Spectrometer)
The largest scientific payload expected for the ISS employs an important technological support: more than 200,000 readout channels, microprocessors 650, 450 for a total of 30 crates electronic cards for a consumption of 2.5 kW / p. Its dimensions are remarkable, more than three meters on each side for a total weight of 7.5 tons.
The realization of AMS has required the development and space qualification of numerous technologies, many of which were developed in Italy by Italian industries and laboratories of INFN.
The more sophisticated component is certainly the cylindrical superconducting magnet, operated at 1.4 ° K and cooled by dry contact with a flow of superfluid helium. This is the first superconducting magnet designed to operate in space. It ‘made with thin wire of niobium and copper coextruded with pure aluminum, to stabilize the thermal behavior and avoid the phenomenon of the “quench” – the rapid transition from superconducting to normal conductor which occurs in the presence of thermal fluctuations.
The weight of the magnet is 2.2 tons, to which must be added to 2600 liters of helium, necessary for maintaining the cryostat at low temperature for a period of at least three years. The magnet comprises coils 14, arranged so as to create an intense magnetic field of 0.8 T within the cylinder. In this way it is possible to reset the component of magnetic dipole magnet and the resulting moments of forces induced by the interaction with the Earth’s magnetic field.
Superconductivity is a technology that can be very useful in space, ensuring strong magnetic fields, light structures and zero consumption. For this reason the technology magnet AMS is interesting for other applications: shielding astronauts from cosmic radiation during long periods in deep space, on the moon or Mars, energy storage and components of propulsion systems plasma. In particular, the first application is of great interest in the context of human planetary exploration projects. There are in fact, at the time, reliable solutions to the problem of ionizing radiation absorbed by an astronaut on a mission to Mars. There are placed around the magnet particle detectors. They allow, in times of a few hundred microseconds, the identification of each individual cosmic ray that passes through AMS. The trigger system is able to measure the time of flight of cosmic rays with a precision of about 130 picoseconds. The detector tracer is composed from 2300 silicon chips and measures the position of the particles within the magnetic field with a precision better than 10 microns. With its 7 m2, it is the largest precision tracker ever designed for a space experiment. Finally, the detector rings of light Cerenkov (RICH), characterized by a focal plane consisting of more than 11000 pixels, each capable of measuring a single photon, is a solid state detector capable of measuring the speed of the particles with a precision of one part per thousand.
In the lower part of AMS is an electromagnetic calorimeter weight of over 600 kg, formed by scintillating fibers glued together with thin layers of lead. It ‘a technology derived from the experiment Kloe in Frascati and allows the measurement of’ energy of electromagnetic component of high energy with about 3% accuracy.
Completing the experiment a radiation detector of transition, able to separate electrons and positrons from the hadronic component up to several hundreds of GeV and a pair of star tracker to provide a precise pointing, necessary for the measurement of high-energy gamma with AMS.