  Gas electron multiplier(GEM) detector is used in Cosmic Muon Scattering
Tomography and neutron imaging in the last decade. In this work, a triple GEM
device with an effective readout area of 10 cm X 10 cm is developed, and an
experiment of discriminating between cosmic muon and x-ray based on rising time
is tested. The energy resolution of GEM detector is tested by 55Fe ray source
to prove the GEM detector has a good performance. The analysis of the complete
signal-cycles allows to get the rising time and pulse heights. The experiment
result indicates that cosmic muon and x-ray can be discriminated with an
appropriate rising time threshold.
