Heavy ion irradiation on silicon strip sensors for GLAST

We investigated the damage of silicon strip sensors due to heavy-ion radiation as a check of the in-orbit stability of silicon strip sensors under cosmic-ray irradiation in the five-year gamma-ray large-area space telescope (GLAST) mission. In order to Study single-event effects (SEE), we used Fe ions slowed-down in an absorber, with a resulting linear energy transfer (LET) of 8 MeV/(mg/cm²) on the surface of the sensor. The total doses achieved in two runs were about 8 krd and 22 krd, corresponding to a fluence of about 5 × 10⁷ and 1.5 × 10⁸ ions/cm², respectively. Silicon strip sensor with two different crystal orientations 〈111〉 and 〈100〉 were irradiated. We measured leakage currents and capacitances before and after irradiation to evaluate the damage. The leakage current density was found to increase by about 10 (nA/cm²)/krd, as expected for the ionizing irradiation. No significant changes of capacitances were found. In addition, no coupling capacitors were broken. The observed effects are well within the in-orbit requirements of the GLAST mission.