Heavy ion irradiation test to gas electron multipliers

We have developed the gas electron multiplier (GEM) for applying to a cosmic X-ray polarimeter. For a space use of the GEM, we performed experiments of charged particles irradiation to the GEM as space environmental tests of cosmic rays. The GEM is irradiated with full-striped iron ions with energy of 500 MeV/n, as a result, we found that even if a particle deposits an energy of ~ 2 MeV in the detector, it has no direct effect on the GEM as long as the particle does not hit the GEM directly. In contrast, every time a particle collides with the GEM, it discharges with a probability of 0.4-40% which depending on the count rate, the applied voltage, and energy losses, but the mass of particles does not matter. The predicted count rate of discharges in the space is low enough, so it is negligible compared with a target object. We also found that an irradiation of charged particles for a certain period causes a destruction of the GEM, but the direct reason remains unclear.