GEM detector at work

We describe systematic beam and laboratory measurements, carried out with s ingle and double GEM detectors with printed circuit read-out. The maximum s afe operating gain has been measured at increasing radiation flux, and unde r exposure to heavily ionizing tracks. Detection efficiency, localization a ccuracy, time resolution and avalanche size have been measured in a minimum ionizing particle beam. Two-dimensional localization of radiation is demon strated, with a readout electrode realized by the same GEM technology.