Radiation-Tolerance Testing of FPGA-based, Self-reading Hadron Fluence Sensors

Hadron fluence monitors based on static random access memories are being used at CERN and have been proposed for proton therapy facilities. Some of the limitations of the state of the art are related to the usage of separate components for sensing upsets and for reading them out, as these increase the power consumption, the board complexity and its size. Moreover, due to radiation-tolerance requirements, the readout logic is fixed and it cannot be updated once the system has been implemented. In this work, we describe an hadron fluence monitor using a static-random-access-memory-based field programmable gate array for implementing both the sensitive element and the readout logic. We irradiated two sensors prototypes at the Jožef Stefan Institute’s TRIGA Mark II research reactor, under different neutron flux conditions. We discuss our results, which include the measurements of the radiation tolerance in terms of 1-MeV neutron equivalent fluence and the average number of readable upsets before failure of the readout logic.