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Shanghai Synchrotron Radiation Facility, SSRF 
Date of Last update : 2013.12.09 Rivision Request
Keywords
accelerator, beamline, Synchrotron Radiation
Description
Shanghai Synchrotron Radiation Facility, SSRF, is a third-generation of synchrotron radiation light source, and would be the invaluable tools for Chinese scientific research and industry community. Up to now, SSRF is the biggest scientific platform for science research and technology development in China, and more than hundreds of scientists and engineers from universities, institutes and industries in domestic and even overseas can do research, experiments and R&D by using SSRF each day.

The synchrotron radiation was firstly observed in synchrotron accelerator in 1947. When a circulating electron beam is deflected by the bending magnets in a storage ring, an intense flux of electromagnetic radiation, called synchrotron radiation, is produced. Relativistic effects cause this synchrotron radiation to be emitted in a narrow cone centered about the electron beam direction. Originally, synchrotron radiation was viewed primarily as an annoyance because of the need to compensate for the electron beam energy loss by using a powerful radio-frequency accelerating system. However, it is soon recognized that synchrotron radiation is useful for a wide range of physical, chemical, and biological experiments, quite unrelated to the original purpose of these electron storage ring.

Although the scientific community has taken great advantage of the synchrotron radiation produced by these first-generation light sources (originally constructed for high energy physics, such as BSRF in BEPC in Beijing), the properties of accelerators were not at all optimized for this purpose. From 70s, developed countries, such as the United States, Japan, Germany and England, have designed and constructed electron storage rings specifically dedicated to producing synchrotron radiation. Most storage ring in this so-called second-generation of synchrotron radiation light sources, such as NHLS in Hefei, having big electron beam emittance of 150nm.rad, have become operational in the recent past years. These second-generation facilities, while built expressly for the production of synchrotron radiation, were designed primarily for photon beam lines from bending magnets. Thus, their figure of merit was primarily the integrated flux of photons.

The third-generation of synchrotron radiation light sources, of which the constructed ALS, APS, SPEAR3 in the United States, Spring-8 in Japan, ESRF in Europe, BESSYII in Germany, SLS in Swiss, ELETTRA in Italy, SSRC in Taiwan of China, PLS in South Korea, CLS in Canada, the constructing DIAMOND in British, SOLEIL in France and SSRF in Shanghai, the spectral properties of the photon beams have been considerably enhanced firstly by much smaller beam emittance of 3~20 nm.rad, secondly by utilizing special magnetic insertion devices called wiggler and undulators that are placed in the straight sections of the storage ring. And another twelve third-generation of synchrotron light sources are under design. To the end of year 2010, we expect that more than ten thousands of scientists and engineers will use synchrotron radiation light sources do research each day in the world.
Application Area
- Target of SSRF
As a third generation of synchrotron light source, SSRF’s electron energy is 3.5Gev, which is fourth in the world, only next to Spring-8 of Japan (8GeV), APS of America (7GeV) and ESRF of European Community (6GeV). SSRF consist of a 150MeV LINAC, a booster that can increase the electron energy from 150MeV to 3.5GeV in 0.5 second, and a 3.5GeV electron storage ring. The 20 cell, 4 fold structure is used to store an electron beam (average current 300mA) with low emittance (minimum 4 nmrad) and long lifetime ( >10 hours). By using advanced insertion device, synchrotron radiation light with high flux and high brilliance will be produced, and the range of the photon energy is from 0.1 to 40keV, which have the call of the users. The brightness of the photon is higher than the 19th power of 10. There are 40 bending magnets, 16 standard straights (6.5 meters) and 4 long straights (12 meters) along the ring, so more than 60 beamlines could be installed in the ring, where 26 of them will be based on insertion devices(by installing two mini-gap undulators for several straights), 36 lines are based on bending magnets and several infrared beamlines are available too. SSRF will also include 7 initial beamlines and experimental stations. These 7 beamlines are used for macromolecular crystallography, XAFS, hard X-ray microfocus, X-ray imaging and biomedical application, soft X-ray spectromicroscopy, diffraction and small angle X-ray scattering respectively. The former five beamlines are based on insertion devices, and other two are based on bending magnets.

- Challenge
SSRF is an extremely complex project with many subsystems, most of them are dealt with advanced technology, such as superconductive RF and cryogenic, ultra-high vacuum, ultra-high precision digital power supply, high performance magnets and mechanical collimation, beam diagnosis, advanced control system, and advanced beamline, etc. The difficulty of the system development and integration is very high, especially how to keep the fault rate very low on the premise of ensuring all system’s performance, in order to achieve the targets which can store beam for several tens of hours and provide synchrotron radiation light for more than 5000 hours per year.

Small emittance is necessary for the demand of high brilliance. The horizontal emittance of SSRF is about 4 nmrad, the beam size at the light source point is only about 150μm horizontally and 10μm vertically. But low emittance requirement will make the ring’s dynamic aperture very small, then several beam instability will be introduced in, and the beam lifetime will be shorten too. So it must be studied how to optimize the dynamic property of the light source.

To make the beam stable, the vertical orbit stability must be less than 1μm, this is one of the difficulties of SSRF. Lots of methods are used to satisfy this demand, such as to control the sedimentation of the groundsill, distortion of the tunnel and floor strictly, to restrict the temperature variety of air and water, to monitor and control all vibration source, to optimize the mechanical structure of the device, to close off and damp the vibration, to increase the stability of power supply, and to use orbit feedback system, etc.
Specifications

Accelerators Layout

- 150MeV Electron Linac

- 3.5GeV Booster

- 3.5GeV Storage Ring

- Beam Line and Experimental stations



Beamlines

There are 40 bending magnets, 16 standard straights (6.5 meters) and 4 long straights (12 meters) along the ring, so more than 60 beamlines could be installed in the ring, where 26 of them will be based on insertion devices(by installing two mini-gap undulators for several straights), 36 lines are based on bending magnets and several infrared beamlines are available too. SSRF will also include 7 initial beamlines and experimental stations. These 7 beamlines are used for macromolecular crystallography, XAFS, hard X-ray microfocus, X-ray imaging and biomedical application, soft X-ray spectromicroscopy, diffraction and small angle X-ray scattering respectively. The former five beamlines are based on insertion devices, and other two are based on bending magnets.

- BL08U1-A Soft X-ray Spectromicroscopy

- BL08U1-B Soft X-ray Interference Lithography(XIL)

- BL13W1 X-ray Imaging and Biomedical Applications

- BL14W1 X-ray Absorption Fine Structure Spectroscopy (XAFS)

- BL14B1 X-ray Diffraction

- BL15U1 Hard X-ray Micro-Focusing

- BL16B1 Small Angle X-ray Scattering (SAXS)

- BL17U1 Macromolecular Crystallography