The Alpha Magnetic Spectrometer 02 (AMS-02), a particle physics module mounted on the International Space Station (ISS), will be deployed to search for antimatter in space. This second version of the AMS, is expected to be ready for launch late 2010. The National Aerospace Laboratory (NLR) developed an advanced, space-worthy cooling system for the AMS-02.
NLR developed the Tracker Thermal Control System (TTCS), which maintains the AMS-02 Tracker’s sensitive electronics at the correct temperature. Owing to its expertise in complex, space-worthy cooling systems, NLR was asked to lead this project.
To account for the lack of room inside the AMS-02 Tracker detector and for the distance over which the heat must be transported, the decision was taken to opt for a two-phase system, which is a system that uses a mixture of liquid and vapour to transport heat.
Because the cooling system has narrow tubes, CO² was chosen as the coolant. The density of CO² vapour closely approximates the density of CO² liquid and therefore accounts for only a small increase in the volume of evaporation. A pair of radiators ensures that the waste heat can be radiated to deep space, owing to the fact that these radiators are situated on the side of the AMS-02 that looks out on the stars (that is, the cold side).
Despite the fact that temperatures in the area where the experiments are conducted can vary greatly, due to changes from sun to shadow, the TTCS system maintains the AMS-02 Tracker’s electronics at a constant temperature.. This constant temperature can be raised or lowered for extremely hot or cold conditions. NLR has developed models to predict when the temperature must be reset and at what temperatures this should be. This process occurs for example when space vehicles dock at the ISS, as at such times the ISS changes its position in space.
In 1988, AMS-01 , a first and simplified version of this antimatter detector – was operational in space for a three-week period, during which time it was proven that the system was capable of locating antimatter particles. AMS-02 is equipped with a six-times more powerful cryogenic-cooled magnet. Compared to AMS-01, AMS-02 is not only capable of detecting positrons, but also the heavier (antimatter) particles floating in space, such as anti-helium. AMS-02 is cylindrical shaped and just fits inside a Boeing 747. The present plans call for AMS-02 to operate in space for a three-year period.
