Diffraction Limited Storage Rings – a window to the science of tomorrow

Cover illustration: Artistic impression of the new MAX IV facility, currently under construction in Lund, Sweden, and one of a new generation of storage-ring-based synchrotron light sources employing a multibend achromat lattice to reach emittances in the few hundred pm rad range in a circumference of a few hundred metres. [Image courtesy of FOJAB arkitekter.]

Synchrotron scientists have always been longing for brighter more coherent sources. Today, advances in accelerator technology open new windows of opportunity. These advances have taken the lead in bringing synchrotron X-ray sources closer to their diffraction limit. Using new concepts in magnet design, vacuum technology and an improved understanding of beam dynamics, light sources of unprecedented quality are being and will be built. The users have embraced this challenge and now design instrumentation to exploit this increased performance as well as experiments demanding it. In our common effort to make the invisible secrets of nature visible we have again come one step further. We all look forward to what will be found. A recently published special issue by guest editors Mikael Eriksson and J. Friso van der Veen [Eriksson and van der Veen, (2014), J.Synchrotron Rad.21, 837-1216] provides a comprehensive review of the field with contributions from leading researchers and groups from around the world.

Progress is being made in improving accelerator technology, enabling a significant increase in brightness and coherent fraction of the X-ray light provided by storage rings. Two facilities will open shortly; MAX IV will open to users in 2016, SIRIUS soon thereafter. Many existing facilities are working on upgrades of their present machines based on these concepts, and entirely new machines are under consideration.

These developments cannot come soon enough, because higher brightness of the source will be of advantage for almost any experiment. This is not only the case for numerous X-ray microscopy applications but also if a small spot of the sample needs to be illuminated like in high-resolution X-ray spectroscopy or in experiments under high pressure in a tiny diamond anvil cell.

While diffraction limited storage rings (DLSRs) provide high average brightness, they cannot compete with Free Electron Lasers (FELs) as regards the peak brightness required for ultra-fast time resolution or single-shot experiments. This complementarity makes it attractive to locate a DLSR and a FEL on the same site. In this case a large number of scientific experiments can be conducted simultaneously on many beamlines at the DLSR, while specialized experiments can be scheduled for the FEL, at which only one or a few experiments can be conducted at a given time.

Exploitation of the full potential of a DLSR requires near-perfect optics, dedicated beamlines and sample environments, and specialized detectors. Together they can produce huge data rates (~10 GB/s) and data volumes (~10 TB/experiment) requiring dedicated infrastructure and specialized software that also allows non-expert synchrotron users to extract the relevant information within a realistic time.

Light sources are a tool to see the world around us and storage rings are nothing but light sources for the X-ray range. The significant improvement provided by the DLSRs under construction and in the design stage will enlighten our view of the world and allow science which is not possible, or not even thinkable, today.

We hope you enjoy this special issue and our glimpse into the science of tomorrow.

Mikael Eriksson, J. Friso van der Veen and Christoph Quitmann