Upgrade of the cold electronics of the ATLAS HEC calorimeter for sLHC generic studies of radiation hardness and temperature dependence

The front-end electronics (signal amplification and summation) of the ATLAS Hadronic End-cap Calorimeter (HEC) is operated at the circumference of the HEC calorimeter wheels inside the cryostats in liquid argon (LAr). The present electronics is designed to operate at irradiation levels expected for the LHC. For operation at the sLHC the irradiation levels are expected to be a factor ten higher, therefore a new electronic system might be needed. The technological possibilities have been investigated. For different technologies generic studies at the transistor level different have been carried out to understand the radiation hardness during irradiation up to integrated n fluxes of 2 × 10
¹⁶
n/cm
²
and the behaviour during cool-down to LAr temperatures. An S-parameter technique has been used to monitor the performances during irradiation and cool-down. In addition, DC measurements before and after irradiation have been compared. Results of these investigations are reported. Conclusions are drawn and the viability is assessed of using technologies for carrying out the design of the new HEC cold electronics for the sLHC.