Shanghai light source

Shanghai light source

This entry is compiled and applied by "popular science China" Science Encyclopedia

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Shanghai Synchrotron Radiation Facility (SSRF) is a high performance third generation synchrotron radiation source. The project includes three accelerators, one is a 150 MeV electron linac, one is a full energy intensifier that can increase the electron beam energy from 150 MeV to 3.5 GeV in 0.5 seconds, and one is a 432 meter high-performance electron storage ring. The project was started on December 25, 2004 by Shanghai Institute of Applied Physics, Chinese Academy of Sciences, located in Zhangjiang High Tech Park, Pudong, Shanghai In April 2009, the debugging was completed and opened to users.

geographical position

SSRF (Shanghai Synchrotron Radiation Facility) is a national large-scale scientific device and multi-disciplinary experimental platform located at 239 zhangheng Road, Zhangjiang High Tech Park, Shanghai.

From December 25, 2004 to April 2009, the project will be open to users. On the afternoon of January 19, 2010, it successfully passed the national acceptance. It marks that the performance index of China's third generation synchrotron radiation source has reached the world-class level. After ten years of project approval and 52 months of intensive construction, the project construction has been completed comprehensively, with high quality and on schedule.

Layout structure

Shanghai light source is an extremely complex science project, which includes many systems, including superconducting high-frequency and low-temperature technology, ultra-high vacuum technology, high-precision digital power supply technology, high-performance magnet and mechanical collimation technology, high-performance beam diagnosis technology, advanced control technology, advanced beamline technology and many other advanced technologies. It is difficult to develop components and integrate systems In particular, it is necessary to achieve a very low failure rate on the premise of ensuring the performance of each system, so as to achieve the predetermined goal of providing a stable beam current of more than ten to dozens of hours and a light supply time of more than 5000 hours per year.

Overall structure

Shanghai light source is an advanced third generation synchrotron radiation source. It consists of a full energy injector, including a 150 MeV electron linear accelerator, a 180 meter perimeter full energy intensifier and injection / extraction system that can accelerate the electron beam from 100 MeV to 3.5 GeV in 0.5 seconds, a 432 meter perimeter 3.5 GeV high-performance electron storage ring, and the first batch of 7 + 1 outer ring It is composed of a synchrotron radiation beamline station and an experimental station.

The average current intensity is 300mA, the minimum emittance is 4nm radian, and the beam lifetime is more than 10 hours. Equipped with advanced inserts, it can generate high-throughput and high flare synchrotron radiation light in the photon energy region (0.1-40kev) where users need the most, and the photon brightness is greater than 1019. The storage ring has 40 bending dipole magnets, 16 6.5m standard linear sections and 4 12m super long linear sections. It has the ability to install more than 60 beam lines, including 26 insert beam lines, 36 bent iron beam lines and several infrared beam lines. It can supply light for nearly 100 experimental stations at the same time. The first batch of five inserter based beamline stations are biological macromolecular crystallography line station, XAFS line station, hard X-ray micro focusing and application line station, X-ray imaging and biomedical application line station, soft X-ray scanning microscope line station; the second beamline station based on bending magnet is high-resolution diffraction line station and X-ray scattering line station. In addition, an X-ray interference lithography branch line station based on soft X-ray beamline will be built.

Each year, it will supply more than 5000 hours of light and machinery, and can accommodate hundreds of scientific researchers every day. Synchrotron radiation is used in their own experimental stations for multidisciplinary frontier research and high-tech development and application.

storage ring

In this huge circular device, the full energy injector provides the electron beam and accelerates it to the required energy. Countless electron beams run in the closed ring vacuum electron storage ring at the speed close to light, and emit synchrotron radiation when turning. Electronic storage ring is the main body and core of synchrotron radiation light source, and its performance directly determines the performance of synchrotron radiation light source. In order to provide users with highly stable synchrotron radiation light in space, the stability of electron beam orbit needs to be controlled in micron level.

Beamline

The beam line is distributed along the outside of the electronic storage ring, which acts as a bridge between the user experimental station and the electronic storage ring. In other words, this "shutter" will "analyze" the synchrotron radiation beam from the electronic storage ring into synchrotron radiation beams with different wavelengths from far infrared to hard X-ray, and then carry out collimation, focusing and other reprocessing according to the user's requirements, and then deliver them to the user's experimental station.

radiation protection

Shanghai light source project has taken many measures to protect high intensity and high brightness X-ray radiation. Around the periphery of the storage ring with a circumference of 432 meters, a shielding wall with a thickness of more than 1 meter of reinforced cement was built, and the shielding was thickened in some areas. Outside the shielding wall, X-rays were led out to the optical and experimental sheds made of lead, because X-rays could not penetrate lead.

In order to ensure that there is no one in the experimental ring after the light source is turned on, in addition to using video monitoring, broadcast notification, ringing, flashing lights and other prompts, the operation Department of Shanghai light source will also send special personnel to carry out safety search. Hundreds of emergency buttons are installed in the experimental device of Shanghai light source. Pressing any button after the light source is turned on, the machine will immediately cut off the power supply and stop generating X-rays to ensure personal safety, This safety control system adopts international safety standards. Every time when the machine is shut down for maintenance, Shanghai light source also stipulates that it must ventilate for 40 minutes before it can enter for maintenance after passing the safety test of the radiation dosimeter.

A total of 52 pairs of neutron and gamma ray detectors have been installed in the park of Shanghai Institute of applied physics where Shanghai light source project is located, and a special radiation monitoring network for the environment around the light source project has been established.

The radiation level of the experimental hall of Shanghai light source is kept at the background level of Shanghai. All the researchers who enter the hall for light source experiment will wear a "personal radiation dosimeter" as big as a whistle. The staff will regularly check the radiation dose recorded by the instrument, establish a personal file for each experimenter's radiation dose, and specially establish a database.

In addition, Shanghai Institute of Applied Physics has formulated a set of perfect radiation safety management system and compiled special teaching materials to provide pre job safety training for each light source user. The person in charge of each line station should also strictly check the safety of the user's experimental samples in advance.

Construction situation

The hard X-ray micro focusing and application beamline station (bl15u1) is the first vacuum undulator beamline station to be debugged in the first batch of beamline stations of Shanghai light source project. In the afternoon of February 6, 2009, the researchers completed the preparation work before beam tuning, and started the formal beam tuning at 18:00 p.m., then the undulator radiation spot and photocurrent were observed on the beamline fluorescent target and the wire scanning detector, respectively. At 21:30, 5.4% of the undulator radiation was detected on the ionization chamber at the exit of the beryllium window of the experimental station KeV monochromatic light (third harmonic), and scanning the monochromator swing curve under this energy, the first round of beam modulation is achieved. Then, the researchers worked hard continuously to measure the 3-11th harmonic radiation spectrum of undulator light source, complete the measurement of near edge absorption spectrum of Cu and monochromator energy calibration, and measure the fluorescence spectrum of trace element standard samples srm610 (500ppm) and srm614 (1ppm).

The vacuum undulator used in bl15u1 line station is designed and developed by Shanghai Institute of Applied Physics, Chinese Academy of Sciences. It is the first vacuum undulator in China. Vacuum undulator is the key equipment to determine whether the third generation synchrotron radiation source can produce hard X-ray which can be compared with high-energy source. It has complex structure and high process difficulty. It is a light source equipment integrating high-precision magnet technology, ultra-high vacuum technology, precision mechanical transmission and control technology. The undulator used in bl15u1 line station has a total of 80 magnetic cycles, with a cycle length of 25 mm. It adopts a hybrid magnet structure, with a minimum working magnetic gap of 7 mm and a maximum peak magnetic field intensity of 0.95 T. the undulator is a vacuum type structure, with all magnets and support beams in ultra-high vacuum environment. The mechanical transmission adopts a magnetic row taper adjustable and double motor drive scheme, which realizes up and down operation through the control system The magnetic train operates in parallel mode and taper mode. The two vacuum undulators used in the first batch of line stations of Shanghai light source were originally planned to be imported from the United States. Due to the serious delay in the manufacturing period of the company, the project management department of Shanghai light source decided in March 2008 to start the work of developing two vacuum undulators independently. The project management department has transferred technical backbones from relevant systems to form a project team and concentrated on research and development. After equipment research, scheme design, engineering design and review, non-standard equipment manufacturing and standard equipment procurement, equipment assembly and commissioning, it took only 11 months to complete

Chinese PinYin : Shang Hai Guang Yuan