Radiation testing of GLAST LAT Tracker ASICs

GLAST is a next generation high-energy gamma-ray space observatory designed for observations of celestial gamma-ray sources in the energy band extending from 10 MeV to more than 100 GeV. The main instrument, the Large Area Telescope (LAT), consists of a microstrip silicon Tracker, a Calorimeter, an Anticoincidence Detector and the DAQ system. This study summarizes the results obtained during the radiation testing of the ASIC chips used in the LAT Tracker. Both Single Event Effects (SEE) and Total Dose (TID) tests have been performed, as part of the Radiation Hardness Assurance (RHA) for the planned 5 year mission. Heavy ion SEE tests have been performed at the SIRAD irradiation facility at the INFN Laboratories of Legnaro, Italy (LNL) and at the Texas A&M University (TAMU) Cyclotron Institute, with LET values ranging up to ∼80 MeV·cm²/mg. The tolerance of the chips to ionizing radiation has been evaluated with heavy ions, and by irradiating chips with the spherical ⁶⁰Co gamma source of the LNL CNR-FRAE laboratory.