Gas Electron Multiplier Tracking Telescopes for OLYMPUS

The OLYMPUS collaboration is conducting an experiment to measure two-photon contributions to elastic electron scattering. The experiment is taking place at the DORIS storage ring at DESY, Hamburg, Germany using the upgraded BLAST detector from the MIT-Bates Linear Accelerator Center. Gas Electron Multiplier (GEM) telescopes are used to detect scattered leptons at a forward angle to monitor the luminosity. The GEM detectors have been commissioned at the test facility at DESY and were installed along with the main detector in the DORIS storage ring. With the testbeam the performance characteristics such as gain, efficiency, multiplicity, and resolution of the GEMs were studied.