ISIS is a unique facility providing beams of neutrons and muons that allow properties of material to be understood at the scale of atoms. Research from this facility is used for subjects ranging from clean energy through to environment and pharmaceuticals.

The FEA department were asked to assess the temperature distribution and subsequent thermal expansion within the ‘chopper assembly’ which forms part of the “HEDS Beam Stop”. This component forms part of the proton beam safety system of the ISIS linear accelerator so is an important part of the overall system.

The analysis consisted of three phases: steady state heat transfer, transient heat transfer and thermo-mechanical coupled analysis. The third phase uses the results from the initial two phases to determine the relative expansion of the different materials and resultant stresses.

Several designs, varying the materials and profiles of the component, were assessed in this way in order to optimise the stress distribution. The calculated results showed close correlation with test measurements and validated the integrity of the final assembly.

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