Radiation tolerant D/A converters for the LHC cryogenic system

This paper focuses on the selection of a radiation tolerant 12-bit parallel input D/A converter suitable for the signal conditioners for cryogenic thermometry in the LHC. During an initial campaign, some candidate converters were irradiated to determine the most tolerant device. Once this was determined, a massive test was carried out. Some weak points of the selected device were addressed through the use of an external voltage source and a radiation tolerant operational amplifier. The tests show that a system consisting of an AD565 D/A converter, coupled to an external voltage reference and an OPA627 operational amplifier can tolerate a total radiation dose up to 5×1013 n cm−2 and 2100 Gy (Si), thus satisfying the requirements set by CERN.