Ultra-smooth transmission optics advances synchrotron research

Hosted at Lund University, it operates the world´s first fourth-generation storage ring, which uses a multi-bend achromat lattice and innovative accelerator engineering solutions to deliver unprecedented photon beam brightness for research in a wide variety of scientific fields.

Åke Andersson and Jonas Breunlin, researchers in the accelerator development group at the MAX IV Laboratory, said: "Since our 3 GeV storage ring was designed to store an electron beam of so far unprecedented transverse small dimensions and angular spreads, so-called emittance, two diagnostic beam lines were made available for observing and measuring these properties of the electron beam. 

“Our beamlines use a much longer wavelength (visible to middle UV) region within the synchrotron radiation span than is normally used in other beamlines. Consequently, we base our measurements on the Kirchoff’s diffraction theory adapted to the synchrotron radiation emission and focusing. In this way we may use a relatively (compared to X-ray optics) simple optical set-up based on transmission optics. 

“However, to do this we needed very high-quality surface accuracies on our optical components, in order to ensure that the radiation diffraction properties are not hidden by surface roughness or inaccuracies."

Dr Andersson added: "We selected Optical Surfaces Ltd to supply the critical high precision Plano convex lenses at the heart of our beam focusing set-up because of their extensive experience of supply critical optics to synchrotron facilities around the world and excellent technical support. 

“We found Optical Surfaces very helpful in helping us make key decisions, such as choosing plano-convex instead of bi-convex lenses and choosing the optimum optical material offering best transmission down to 200nm. 

“In addition, they were able to advise us small modifications to our design specification that would enable them to manufacture the lenses, three- and four-inch diameters, to our required surface accuracy of Lambda/20 (P-V) and transmitted wave form distortion around Lambda/15 (P-V). All-in-all our experience of working with Optical Surfaces on this project was very good. 

“Accelerator science results from our 3 GeV storage ring, based on the diagnostic beam lines will be presented at the International Particle Accelerator Conference (IPAC 2019) now in May."

Dr Aris Kouris, Sales Manager at Optical Surfaces, commented: “We were very pleased to be approached by the MAX IV laboratory to discuss the optical requirements of their demanding synchrotron beam line project. This allowed us to exactly understand their needs and deliver the ultra-high quality plano-convex lenses their ground-breaking work needed."