Paper 13100-143
Surface error correction of ELT primary mirror hexagonal segments by ion figuring
On demand | Presented live 19 June 2024
Abstract
Ion Beam Figuring is a key technology after polishing, hexagonal cutting and integration to obtain ELT-M1 hexagonal segments without edge effects. This process used at REOSC over 30 years offers an efficient solution for finishing these large freeform optical components. This paper presents a dedicated figuring process strategy to maximize throughput and process convergence as well as to limit temperature increase during processing. We analysed the results of optical surface improvement over 100 ELT-M1 segments. These results highlight the high accuracy of IBF technology to correct hexagonal surfaces all the way to the edge. The final surface figure error below 10nm RMS was obtained while keeping low surface roughness. This is achieved after less than two figuring iterations leading to a throughput over one segment per day.
Presenter
Camille Frapolli
Safran Reosc (France)