GEM detector at work

We describe systematic beam and laboratory measurements, carried out with single and double GEM detectors with printed circuit read-out. The maximum safe operating gain has been measured at increasing radiation flux, and under exposure to heavily ionizing tracks. Detection efficiency, localization accuracy, time resolution and avalanche size have been measured in a minimum ionizing particle beam. Two-dimensional localization of radiation is demonstrated, with a readout electrode realized by the same GEM technology. (17 refs).