Thermal Neutron-Induced SEUs in the LHC Accelerator Environment

In addition to high-energy hadrons, which include neutrons, protons, and pions above 20 MeV, thermal neutrons (ThNs) are a major concern in terms of soft error rate (SER) for electronics operating in the large hadron collider (LHC) accelerator at the European Organization for Nuclear Research (CERN). Most of the electronic devices still contain Boron-10 inside their structure, which makes them sensitive to ThNs. The LHC radiation environment in different tunnel and shielded areas is analyzed through measurements and FLUKA simulations, showing that the ThN fluence can be considerably higher than the high-energy one, up to a factor of 50. State-of-the-art commercial-off-the-shelf (COTS) components such as SRAM, field-programmable gate arrays (FPGA), and Flash memories of different technologies are studied to derive the expected single-event upset (SEU) rate due to ThNs, relative to the high-energy hadron contribution. We find that for the studied parts and most of the accelerator applications, ThNs are the dominating source of upsets with respect to the high energy particles yielding even to neglect the latter in some cases. Indeed, they can induce, in electronics, up to more than 90% of the total upsets. The estimation is performed also for ground-level and avionic applications, and although in general, ThNs are not the main source of SER, in Flash memories they can play the same role as high energy neutrons. Related radiation hardness assurance (RHA) considerations for the qualification of components and systems against ThNs are presented.