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Description
The ESS Chip Irradiation (ECHIR) beamline has been proposed at the European Spallation Source (ESS) to provide a high-flux, atmospheric-like neutron energy spectrum for Single Event Effect (SEE) testing. SEEs in microelectronics are mainly induced by high-energy atmospheric neutrons, which can cause significant functional disruptions in electronic systems. Fast neutrons can be used to simulate radiation induced effects in an accelerated timeframe, allowing efficient testing of components. The availability for SEE testing in Europe is currently limited, with ChipIR at ISIS being the only facility able to deliver a suitable neutron spectrum for studying these effects. ECHIR has been proposed at ESS to meet the growing demand for such testing facilities.
Due to the high-flux neutron environment at ESS, the beamline design includes significant neutronic challenges. To ensure that the experimental hall and adjacent areas remain safe for users, the radiation shielding must be designed to meet the strict safety requirements set by ESS. This work presents the preliminary neutronic calculations, performed with Monte Carlo N-Particle transport code (MCNP6.3). The simulation models the neutron production starting from 2 GeV protons on a tungsten target. The generated neutrons are then transported through the beamline geometry. To improve the efficiency of the transport, weight windows were used for variance reduction.
These simulations tested different shielding configurations and material combinations, focusing on comparing regular concrete with heavy concrete (MagnaDense). In all cases, stainless steel was included in the shielding configuration. The simulations were performed to calculate the neutron dose rate at key locations using F4-tallies with flux-to-dose conversion factors. Additionally, the dose rate in the rooms were mapped with a TMESH tally and suitable flux-to-dose conversion.
The simulation results show that with appropriate configuration and material choices the neutron dose rate can be significantly reduced at key locations. Using MagnaDense reduces the dose rate by approximately a factor of 2 in comparison to regular concrete. The results show that the tested shielding configuration can meet the safety requirements set by ESS (<3 µSv/h or <25 µSv/h, depending on radiation area classification). Future neutronic simulation work includes optimizing and refining the shielding configuration, as well as studying the activation of the materials.