Irradiation of CMS Readout Chips with Gammas from ⁶⁰Co

Experimental testing of silicon pixel sensors and their readout chips is a vital part of preparing for the next generation of particle detectors. The Compact Muon Solenoid (CMS), located in France, is a detector in the Large Hadron Collider (LHC). Determining the path the particles take in the CMS detector, and therefore the charge and momentum, utilizes, in part, silicon pixel sensors. The upcoming high-luminosity upgrade of the LHC will increase the number of collisions by a factor of 5 to 7.5. For the pixel sensors to work reliably for 10 years after being put in place the pixel sensors need to function up to 1 GRad of radiation dose. To test the newest version of the electronics we used a Cobalt 60 source which produced gammas with about 1MeV of energy. Because the electronics and radiation effects are affected by temperature, we kept the electronic card dry at -20 °C using a boil-off liquid nitrogen system. The irradiation took place over 28 days, and we maintained communication with the card for most of the irradiation. The card behaved well and allowed us to perform tunings up to 1.6 GRad. The card seems viable up to and exceeding the expected dose over the course of 10 years.