Characterisation of additively manufactured synchrotron radiation absorbers for FCC-ee manufactured by green laser-based powder bed fusion

FCC-ee is a proposal for 92 km circumference twin ring which would generate a synchrotron radiation (SR) power of 50 MW/beam. Design studies call for the SR fan to be intercepted every ~5m with localised absorbers. Compared to the continuous design (when the synchrotron radiation absorber (SRA) channel is located all around the ring), this design is advantageous due to faster conditioning of the vacuum chambers, lower material and manufacturing costs. The proposed design uses turbulent water flow to remove generated heat. The use of additive manufacturing (AM) was chosen due to the ability to achieve complex structures in a shorter time and with lower material consumption, making it ideal for SRA production. Tests were done to analyse if the manufactured part adheres to the requirements, including CT, 3D scans, SEM and EDX analysis, hardness and tensile tests, additionally, thermal transfer and helium leak tests were planned to validate further the design and manufacturing method used in FCC-ee. It was found that LPBF method can produce geometrically accurate complex objects, however, as-built copper does not have the necessary yield strength to withstand projected forces during the beam activity period.