A measurement of the cosmic ray positron fraction e ^ { + } / ( e ^ { + } + e ^ { - } ) in the energy range of 1–30 GeV is presented .
The measurement is based on data taken by the AMS-01 experiment during its 10 day Space Shuttle flight in June 1998 .
A proton background suppression on the order of 10 ^ { 6 } is reached by identifying converted bremsstrahlung photons emitted from positrons .