Cosmic Rays at the ALMA sites: impact on thin gate-size electronics and radiation exposure

Generation in the Earth's atmosphere of multiple secondary Cosmic Rays (CRs) impacts the (ultra)thin gate size electronics embedded in many modules of the ALMA Wideband Sensitivity Upgrade (WSU) project. Around 5.6x10$^{-5}$ Single Event Upsets (SEUs) per device and hour have already been observed in the FPGAs of the current correlator. Despite advances in integration designs and configuration integrity testing in the latest FPGAs, Single Event Effects (SEEs) are expected to appear in devices that format the digital samples at the AOS antennas and, later, in the WSU correlator at the OSF. We have used our multi-applications numerical platforms to successfully compare the Software Error Rate (SER) observed in the current correlator with our simulations to extract the neutrons (dominant risk) and protons cross-sections and SER at the ALMA sites. A first, rough prediction at the level of $\sim$10 events per month in the 226 Agilex FPGAS (10-nm) of the WSU correlator could be closely examined with our numerical tools, including the impact of extreme Solar events. Biological cells are also impacted by the CRs. We evaluate the yearly dose exposure to be $\sim$4.8 mSv (AOS) and $\sim$1.8 mSv (OSF) with additional ambient dose up to $\sim$1 mSv (Solar events). We propose to deploy at the ALMA sites a compact, low power consumption, remotely operated neutron spectrometer similar to spectrometers used in Antarctica and on top of high mountains for a precise SEE analysis and space weather monitoring.