The occurrence of discharges in gas detectors is correlated
with the transition from avalanche to streamer.
The transition depends on the voltage and ionization density.
In this case the total charge created by the multiplication processes could
exceed the threshold value (Raether limit, 10^710^8 e I+ pairs) for the
transition from avalanche to streamer.
Due to the very small anodecathode distance in GEM detectors, the transition
from avalanche to streamer is most of the time followed by discharges.
Performance with XRay. 

Discharge measurement at PSI. GEM detectors have been tested at PSI with a hadron
beam of 50 MHz 

Discharge probability with 

Discharge probability
with At the working point we reach a discharge probablity of 10^13. With a discharge probability of 10^9 the inefficiency due to the recharge time is 1%. 

Discharge probability with 

During the PSI test each detector integrated
without any damage or aging effect about 5000 discharges, corresponding
to a discharge probability per incident particle of 10^12 in 10 years at LHCb. 