Abstract: A new design of spallation target has been installed and operated at the first target station of the ISIS Neutron and Muon Source (ISIS TS-1), as part of the recently completed “TS-1 Project”. Detailed Finite Element Analysis (FEA) simulations were used to guide the design process and predict target performance. Since the TS-1 Project target began operation in November 2022, operating data has been collected and used to validate the target simulation approach. Measured temperatures of 9 out of 10 target plates showed good agreement with FEA simulations of both steady-state and transient behaviour. However, the front target plate temperature was elevated compared to predictions. Because the installed target was now too radioactive to permit hands-on inspection, FEA simulations became an indispensable tool to understand the possible causes and safety implications of this anomalous behaviour. The anomalous elevated temperature appears to be highly localised; a combination of simulations and experiments indicates the mostly likely cause is poor thermal contact between the thermocouple and the bulk of the target plate. In all other respects the target is operating as predicted, and is running reliably at up to 120 kW.
