Ultrasmooth transmission optics enable advances in synchrotron research in the visible to mid-UV region

Plano convex lens being installed (Courtesy of MAX IV Laboratory)

The MAX IV Laboratory, Sweden's national synchrotron radiation facility hosted at Lund University, operates a 3 GeV storage ring that uses a transmissive multibend achromat lattice in its diagnostic beamlines to deliver high photon-beam brightness for research in a wide variety of scientific fields; its diagnostic beamlines use much longer wavelengths (visible to mid-UV region) within the synchrotron radiation span than the x-ray radiation normally used in other beamlines.

"Consequently, we base our measurements on Kirchoff's diffraction theory adapted to the synchrotron radiation emission and focusing," say Åke Andersson and Jonas Breunlin, researchers in the accelerator development group. "In this way, we may use a relatively (compared to x-ray optics) simple optical setup 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."

"We selected Optical Surfaces Ltd. [Kenley, England] to supply the critical high precision plano-convex lenses at the heart of our beam focusing setup because of their extensive experience supplying critical optics to synchrotron facilities around the world and excellent technical support," notes Andersson. "We found Optical Surfaces very helpful in helping us make key decisions, such as choosing plano-convex instead of biconvex lenses and choosing the optimum optical material offering best transmission down to 200 nm. In addition, they were able to advise us of 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 peak-to-valley (P-V) and transmitted wavefront distortion around Lambda/15 P-V."

Manufacturing deep underground
Optical Surfaces makes large high-precision optics and optical systems for synchrotron research (as well as other optics, including ultrafast-laser mirrors, optics for fusion research, and hyperboloids). The company's ISO 9001-2008 approved manufacturing workshops and test facilities are deep underground in a series of tunnels excavated in solid chalk, where the temperature remains constant and vibration is practically nonexistent. With such stable conditions, testing, particularly with long path lengths, becomes quantifiable and reliable, says the company.

Accelerator science results from the MAX IV Laboratory's 3 GeV storage ring, based on the diagnostic beamlines, were presented at the International Particle Accelerator Conference (IPAC 2019; Melbourne, Australia -- May 19-24, 2019).

For further information on high-precision optics for synchrotron research, see www.optisurf.com.

Source: Optical Surfaces