Shanghai synchrotron radiation facility

Synchrotron radiation was discovered by chance at an electron synchrotron accelerator in 1947. The first experiments applying synchrotron radiation were conducted in the early 1960s, with measurements using synchrotron radiation for standards and as a source for ultraviolet wavelength spectroscopy. Synchrotron radiation later attracted considerable interest for use in solid-state physics research. With increased development of both facilities and applications, a surge of interest in synchrotron radiation rose in the 1970s [1,2]. Interest boomed further in the following decades with the emergence of dedicated second-generation and third-generation synchrotron radiation facilities, and has shown no signs of reaching its apex. Even now, synchrotron radiation is being used extensively and intensively in multidisciplinary fields. The Shanghai Synchrotron Radiation Facility (SSRF) project was formally proposed in 1995. The goal of this project was to build an advanced third-generation synchrotron radiation light source for Chinese scientists to perform the frontier scientific research which could not be carried out in China before. It took about 10 years to begin the construction of SSRF, with groundbreaking beginning in 25 December 2004. This gave sufficient time for research and development of the SSRF, and this detailed technical preparation in turn made construction of the SSRF proceed smoothly, with successful completion in April 2009. The SSRF project (Phase-I), was jointly funded by the Central Government of China, the Chinese Academy of Sciences and the Municipality Government of Shanghai. It consists of a 150-MeV electron linear accelerator, a full energy booster synchrotron, a 3.5-GeV storage ring with a 432-m circumference and seven Phase-I beamlines. The design specifications of the SSRF were achieved and, in some cases, exceeded. The key parameter of the storage ring is the natural emittance, which gives an indication of the synchrotron radiation brilliance. The SSRF natural emittance initially reached 3.9 nm rad, and was further improved to 2.9 nm rad, which is among the best values that only a few existing light sources have achieved. The overall performance of the SSRF places it among the top intermediate energy light sources in the world [3,4]. The SSRF Phase-I beamlines include seven beamlines as follows: macromolecular crystallography, X-ray absorption fine structure (XAFS), diffraction, hard X-ray micro-focusing, X-ray imaging, soft X-ray spectromicroscopy and small angle X-ray scattering (SAXS). They are aimed at providing facilities for the research fields of life sciences, physics and materials science, chemical science, earth and environmental sciences, medicine, archeology, interdisciplinary, and industrial applications. The SSRF started user operation on 6 May 2009, with seven Phase-I beamlines fully open to users. Since that time, all seven beamlines have witnessed a rapid increase of user demand and outstanding research results, with four times over subscription for beamtime on average and more than one thousand published journal papers so far, including 27 papers in Nature and Science. Structural biology research in China has benefited greatly from the use of the SSRF. The operation of the SSRF immediately changed the situation, which forced scientists in mainland China to primarily rely on foreign synchrotron radiation facilities to solve protein structures. The SSRF allows these scientists to finish their work in a timely way, which is a critical support to their research projects; especially to those working on competitive scientific frontiers. Many outstanding results have been achieved in recent years, including the sequence-specific DNA identification mechanism of the transcription activator-like effector [5], referred to in ‘Genomic Cruise Missiles’ of Science magazine's 2012 ‘Breakthroughs of the Year’ and also selected into ‘China's Top Ten Science Advances’ of 2012; the cross-species transmission of avian influenza [6]; and structural determination of many important membrane proteins and protein complexes. In materials science, SSRF users have carried out a number of studies on the structure of new materials and property modification of materials, including iron-based superconductors, hydrogen-storage materials, magnetic semiconductors, piezoelectric/ferroelectric materials, crystalline materials, and polymeric materials. Some of their achievements show interesting prospects for broad and important applications, such as re-emerging superconductivity at high pressure for iron chalcogenides [7] and systematic studies of graphene liquid crystals leading to the successful fabrication of ultra-strong graphene fibers [8]. Research into novel catalysts is another active field at SSRF. Understanding and controlling chemical reactivity by catalysts at the scale of atoms and electrons can have a profound impact upon chemical energy conversion and use. By using both in situ and ex situ XAFS and X-ray diffraction experimental methods, scientists in China have made considerable progress in understanding the mechanisms of novel catalysts [9]. In environmental science and biomedicine, many experiments with particular features have been conducted by the SSRF users, and many interesting results have been obtained. These include studies on the distribution and transport mechanisms of toxic elements and chemical compounds in rice and vegetables [10], and the mechanism of arsenic adsorption in industrial waste water [11]. In addition, studies on high-resolution imaging of mouse lungs [12], cardiocerebral vasculature and tumor tissue are paving the way for clinical applications of medical imaging. Industrial applications have also shown an encouraging upward trend. Gaining benefits from their research at SSRF into new drug development, chemical engineering and chemical identification techniques, more than 30 enterprises have used SSRF for their research and development activities to this point. Even with only seven beamlines in operation, the SSRF is playing an important role in supporting thousands of users in various fields. The Phase-I beamlines are using only a small portion of the capacity of the SSRF, which can be optimized to accommodate up to 60 beamlines. This huge potential is being explored and developed to promote the innovation capability in many fields of science and technology in China. Programs developing more beamlines have already been underway for a few years, and the construction of five new beamlines dedicated to protein science and one high-performance beamline dedicated to quantum functional materials are approaching completion, while the construction of another two beamlines dedicated to the research of new energy materials has already begun. A large cluster of new beamlines, the so-called SSRF Phase-II beamline project, have been proposed. Phase-II project aims at promoting the overall performance and experimental capability of the SSRF to the world leading level, and to better meet national strategic needs and important scientific challenges. When the SSRF Phase-II beamline project will be completed, which is projected to be by 2020, the SSRF will be a highly advanced platform supporting cutting-edge user research and forming one of the world's most important photon science centers.