Alpha Magnetic Spectrometer
Alpha Magnetic Spectrometer (AMS ) refers to two magnetic spectrometer ( particle ) to study the cosmic radiation. AMS -01 was on a mission by the space shuttle in space, AMS -02 is long-term to the International Space Station in use.
AMS -01
The prototype AMS -01 has been successfully tested in 1998 during a ten-day flight aboard the space shuttle Discovery (STS -91). The AMS -01 experiment was permanently installed in the cargo bay of the Space Shuttle in this flight.
Even in this short flight, the traces of over 100 million charged particles of cosmic radiation could be measured. Notes on complex antimatter (ie atomic nuclei or atoms of several anti-particles ) were not found, the previous experimental limits were significantly improved. A total of about 3 million helium nuclei ( alpha rays ) were detected. Among them was not a single anti - helium nucleus.
AMS -02
The AMS -02 experiment is a modern particle detector, which was measured from the year 2010 for a period of three years initially on the ISS, the composition of cosmic rays. The decision to operate the ISS by 2020, the spectrometer in 2010 was revised again shortly. Here, the liquid helium -cooled superconducting magnet with the spectrometer was replaced by a normal neodymium permanent magnet to allow an operation of the AMS -2 for up to 18 years. The superconducting magnet would have survived only about three years. It is true that the waiver of the cooled magnets also a loss of measurement precision, since the magnet must guide the charged cosmic particles through five different detectors. This loss can, however, by more sensitive detectors and the longer measurement time is more than compensated. The crash of the space shuttle Columbia in 2003, the original start date of 2003 to 2011 has shifted. AMS -02 was launched on 16 May 2011 aboard mission STS -134 to the International Space Station and was placed on 19 May 2011 at its position on the far side of the truss element S3.
Scientific tasks
The responsibilities of AMS- 02, the search for antimatter is one as it is expected by some cosmological models as a relic from the Big Bang in the frame. The detection of a single anti- carbon core would prove the existence of stars of antimatter in the universe, because carbon could not be formed in the Big Bang. In addition, AMS -02 is able to measure the energy spectra of heavy nuclei, to iron. These data will allow to better understand the propagation mechanisms of charged particles in the Milky Way and thus provide the key to look with great accuracy by the Annihilationsprodukten of dark matter. In the context of supersymmetric models or from Kaluza-Klein theories anomalies are predicted in the energy spectra of positrons, antiprotons and photons, which could possibly be detected by AMS -02.
Detector Description
AMS -02 has a mass of 8.5 tonnes, the dimensions are 3.1 m × 3.4 m × 4.5 m and the geometrical acceptance is 0.5 m² sr. For the central component of the detector was originally a superconducting magnet with a maximum field strength of 0.86 Tesla, which had been cooled to 1.8 Kelvin with superfluid helium, planned. This was replaced at run- time extension of the AMS -02 by the 1200 kg heavy neodymium permanent magnet of AMS- 01 with 0.15 Tesla. In the interior of the magnet is a double-sided silicon strip detector is structured with an active area of 6.5 m². So that the passage of charged particles on eight levels is measured with a single point resolution of 10 microns. The trajectories of charged particles are curved in the magnetic field of this magnetic spectrometer. Based on the curvature of the momentum of the charged particles and the sign of charge can be determined up to particle energies of 1000 GeV. The stability of the tracking detector is monitored using a laser alignment system with a precision of 5 microns. The side of the track detector from the Anti- Coincidence Counter ( ACC) is surrounded, which is to detect the lateral passage of charged particles. By means of a star sensor, and a GPS receiver, the exact orientation of the experiment is monitored on the basis of fixed stars.
To determine the mass of the charged particles, the experiment above by a transition radiation detector ( TRD) and down through a ring - image Cherenkov counter ( RICH ) and an electromagnetic calorimeter ( ECAL ) is completed. To measure the flight times and the velocities of the particles and trigger the readout electronics of the other detector components are located above and below the silicon tracking detector, a time-of- flight (ToF ) which has a time resolution of 150 ps. The experiment generated by the thermal power of about 2000 watts radiated by means of radiators into space.
The experiment produces a data rate of about 7 Gbit / s ( gigabits per second). By processing the data rate is reduced to 2 Mbit / s, and then transmitted to the ground.
Organization
AMS was built by an international collaboration that includes 500 physicists from 56 research institutes from 16 countries, in close cooperation with NASA. The project was initiated by Nobel Laureate Samuel Chao Chung Ting of the Massachusetts Institute of Technology, who still manages it today. In Germany, the I. Physical Institute of the RWTH Aachen University and the Institute of Experimental Nuclear Physics, Karlsruhe Institute of Technology in the experiment involved. The research will be promoted in Germany by DLR.
Results
In April 2013, the AMS collaboration published the first results of the experiment. These 30 billion particles were analyzed, including more than 400,000 positrons. With the observed by the Fermi telescope and Pamela excess of high energy positrons could be confirmed.