Time analysis of the light pulses on gaseous active scintillators using GEMs with He/CF4

The time structure of light pulses from GEM detectors operated in scintillation mode with He/CF4 mixtures, previously used with integrating readout devices for neutron detection, has been investigated. A system using photomultipliers (PMs) and charge preamplifiers coupled to a fast digitizer has been used to measure simultaneously both the charge and light signals of the avalanches and the dependence of these signals on the operating conditions of the GEM, such as gain, transfer yield and collection field. The present results show that detectors relying on photon counting techniques, using of position sensitive PMs or arrays of avalanche photodiodes, are most promising as fast position sensitive neutron detectors.