With rapid advances in low-emittance synchrotron light sources and X-ray free-electron lasers, numerous extremely bright and highly coherent X-ray sources have been established or are under construction worldwide. These facilities have opened a new era in scientific research with X-rays. The resulting demand for high-quality X-ray optics has driven to new frontiers X-ray optics and the related ex situ/in situ metrology. Unlike visible light optics, optics for X-rays, such as X-ray mirrors, requires unique manufacturing and metrology tools and methods, so there are only a handful of commercial suppliers worldwide.
Since being founded more than a decade ago, the International Workshop on X-ray Optics and Metrology (IWXM) has been held every three years as a satellite workshop of the International Synchrotron Radiation Instrumentation (SRI) Conference. It provides a unique platform for X-ray mirror and metrology developers and experts from both industry and synchrotron facilities to present their latest research and products and discuss future directions. Following up on past success, the 6th edition of IWXM was held at the Taiwan Photon Source (TPS), National Synchrotron Radiation Research Center (NSRRC), in Taiwan, on June 6-9, 2018, as a satellite workshop for the SRI Conference.
The number of IWXM participants has grown steadily since its inception, spawning a vibrant community. In 2018, IXWM was attended by 95 delegates from 14 countries (Fig. 1). There were 37 oral presentations with 28 posters covering the latest research achievements in X-ray optics, especially mirror optics and their metrology, including new concepts, equipment, and advances in X-ray optical systems.
This Special Topic gathers a set of 18 peer-reviewed articles derived from a subset of the full workshop presentations. The papers by Takehiro Kume et al.,1 Yoshio Ichii et al.,4 Haruhiko Ohashi et al.,9 Ahmed Akarid and Francois Polack,12 and Tunhe Zhou et al.15 discuss tools and methods to fabricate and optimize X-ray mirrors and gratings with challenging shapes and extreme requirements for surface figure accuracy.
Duan-Jen Wang et al.,2 Valeriy V. Yashchuk et al.,3 Francois Polack et al.,5 Ian Lacey et al.,6 Amparo Vivo et al.,7 Muriel Thomasset et al.,10 Maurizio Vannoni and Idoia Freijo Martín,13 Pablo Pedreira et al.,14 Frank Siewert et al.,16 and Ralf D. Geckeler et al.17 present ex situ metrology instrumentation and characterization methods. Their papers feature research devoted to tools, protocols, and methods to characterize the quality of the surface figure and finish of X-ray mirrors within a well-defined spatial frequency range, precision, and accuracy. They also cover calibration tools and methods for high precision metrology instrumentation for X-ray optics.
To exploit the full potential of the new generation of light sources, in situ metrology and wavefront sensors are becoming increasingly important as diagnostic and monitoring tools to characterize and optimize beamline optics and performance. The ongoing research achievements in these areas are nicely illustrated in the papers by Shang-Wei Lin et al.,8 Vivek Badami et al.,11 Tunhe Zhou et al.,15 and Simon G. Alcock et al.18
A highlight of the workshop was the presentation of the Giovanni Sostero Award for 2018, supported by Sincrotrone Trieste, to Shinan Qian of Brookhaven National Laboratory (USA) for “his original contribution to profilometry, the succeeding improvements implemented in Long Trace Profiler, and the great support given to other laboratories.”
In summary, the workshop succeeded in its objective of reporting on the latest important advances in X-ray optics fabrication and optimization as well as in in situ/ex situ metrology and wavefront sensing.
For more information about the workshop and workshop presentations see the IWXM 2018 website: http://iwxm2018.nsrrc.org.tw/site/page.aspx?pid=901&sid=1203&lang=en.
We thank the International Advisory Committee, Local Organizing Committee, and Selection Committee of the Giovanni Sostero Award for their efforts to make the workshop run smoothly. Daniele Cocco (SLAC, USA), Mourad Idir (BNL, USA), Kawal Sawhney (Diamond, UK), Frank Siewert (Helmholtz Zentrum Berlin, Germany), and Valeriy Yashchuk (LBNL, USA) deserve a warm acknowledgement for their assistance with the workshop organization.
We also thank the workshop sponsors, including the Ministry of Science and Technology of Taiwan, TPS at NSRRC; the International Synchrotron Radiation Instrumentation Conference; and the corporate sponsors CINEL-Scientific Instruments (Italy), Ametek Zygo (USA), Imagine Optic (France), JTEC Corporation (Japan), and Physik Instrumente (Taiwan). Their significant contributions to the community of X-ray optics and metrology are much appreciated.
Special thanks are due to Dr. Jonathan Lang (Editor) and Brian Solis (RSI Assistant Journal Manager), as well as the entire staff at the Review of Scientific Instruments for their assistance in putting this Special Topic together. Work supported by US Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract DE-AC02-06CH11357 at Argonne National Laboratory.