Beam Performance of Tracking Detectors with Industrially Produced GEM   Foils
  Three Gas-Electron-Multiplier tracking detectors with an active area of 10 cm x 10 cm and a two-dimensional, laser-etched orthogonal strip readout have been tested extensively in particle beams at the Meson Test Beam Facility at Fermilab. These detectors used GEM foils produced by Tech-Etch, Inc. They showed an efficiency in excess of 95% and spatial resolution better than 70 um. The influence of the angle of incidence of particles on efficiency and spatial resolution was studied in detail. 
Frank Simon, James Kelsey, Michael Kohl, Richard Majka, Miro Plesko,   Tai Sakuma, Nikolai Smirnov, Harold Spinka, Bernd Sur...