Light multi-GEM detector for high-resolution tracking systems
  Controlled etching of copper electrodes in Gas Electron Multiplier foils allows a reduction of the material budget by more than a factor of two for a triple-GEM detector. Detectors making use of thinned foils provide performances similar to those obtained with standard devices: a gain above 10^4 for a double-GEM, with energy resolution of 27 % fwhm for 5.9 keV X-rays. 
A.Bondar, A.Buzulutskov, R.de Oliveira, L.Ropelewski, F.Sauli and   L.Shekhtman