Alpha Magnetic Spectrometer

• A particle physics experiment module that is to be mounted on the International Space Station.

• It is designed to search for various types of unusual matter by measuring cosmic rays.

• Its experiments will help researchers study the formation of the Universe and search for evidence of dark matter and antimatter.

• The principal investigator is Nobel laureate particle physicist Samuel Ting.

• After the flight of the prototype, Ting began the development of full research system designated AMS-02. This development effort involved the work of 500 scientists from 56 institutions and 16 countries organized under United States Department of Energy (DOE) sponsorship.

• The power requirements for AMS-02 were thought to be too great for a practical independent spacecraft. So AMS-02 was designed to be installed as an external module on the International Space Station and use power from the ISS. The post Columbia plan was to deliver AMS-02 to the ISS by space shuttle in 2005 on station assembly mission UF4.1, but technical difficulties and shuttle scheduling issues have added more delays.[8]

• A cryogenic, superconducting magnet system was developed for the AMS-02. This was a critical technology, enabling a high sensitivity needed to achieve mission objectives.

• Late in its development, poorly understood anomalous heating in the cryogenic magnet system was discovered. The anomalous heating would place additional demand on the cryogenic cooling.

• This characteristic significantly reduced the original system design lifetime and contributed to a decision to abandon the cryogenic system in favor of a previously developed but less capable permanent magnet system. The impact on the original mission objectives have not been described.

• With Obama administration plans to extend International Space Station operations beyond 2015, the decision has been made by AMS management to exchange the original AMS-02 superconducting magnet with the non-superconducting magnet previously flown on AMS-01.

• Although the non-superconducting magnet has a weaker field strength, its on-orbit operational time at ISS is expected to be 10 to 18 years versus only 3 years for the superconducting version. This additional data gathering time has been deemed more important than higher experiment sensitivity although the abandoned cryogenic system was originally described as critical technology to mission success.

• Mass: 14,809 lb (6,717 kg) or 6731 kg (14,839 lb)• Power: 2000–2500 watts• Internal data rate: 10 Gbit/s• Data rate to ground: 2 Mbit/s• Primary mission duration: 10 to 18 years• Magnetic field intensity: 0.125 teslas produced by a 1,200 kg

Nd2Fe14B permanent magnet[17]

• Original superconducting magnet: 2 coils of niobium-titanium at 1.8 K producing a central field of 0.87 teslas[18]

• AMS-02 flight magnet changed to non-superconducting AMS-01 version to extend experiment life

Cost• In 1999, after the successful flight of AMS-01, the total cost of the

AMS program was estimated to be $33 million, with AMS-02 planned for flight to the ISS in 2003.[19] After the Space Shuttle Columbia disaster in 2003, and after a number of technical difficulties with the construction of AMS-02, the cost of the program ballooned to an estimated $1.5 billion.[20]

• The cost of the program was criticized heavily during the period when it appeared that it would not be flown.[6]

• The detector module consists of a series of detectors that are used to determine various characteristics of the radiation and particles as they pass through. Characteristics are determined only for particles that pass through from top to bottom. Particles that enter the detector at any other angles are rejected. From top to bottom the subsystems are identified as:

• Transition radiation detector measures the velocities of the highest energy particles;

• Upper time of flight counter, along with the lower time of flight counter, measures the velocities of lower energy particles;

• Star tracker determines the orientation of the module in space;• Silicon tracker measures the coordinates of charged particles in the

magnetic field;• Superconducting magnet bends the path of charged particles so

they can be identified;• Anti-coincidence counter rejects stray particles that enter through

the sides;• Ring imaging Cherenkov detector measures velocity of fast particles

with extreme accuracy;• Electromagnetic calorimeter measures the total energy of the

particles.