BESSY

The Berlin Electron Storage Ring Society for Synchrotron Radiation ( BESSY ) was the name and legal form of a research institute in Berlin, which provided services for science and industry through the provision of synchrotron radiation. The operating company was founded on 5 March 1979 for the construction and operation of an electron storage ring facility. On November 11, 2009, BESSY GmbH went on for Materials and Energy (HZB ), the former Hahn- Meitner-Institut in the Helmholtz-Zentrum Berlin. The BESSY GmbH longer belonged to from the Leibniz Association, the HZB belongs to the Helmholtz Association. The major equipment BESSY II was next to the research reactor BER II of the two countries on the HZB.

The short name of BESSY is better known as a proper name of each constructed and operated by the Company's electron storage ring BESSY II in the present Berlin- Adlershof.

BESSY I

The 130 million D- Mark (converted 66.5 million euros ) expensive plant BESSY I took on December 19, 1981 to operate at Breitenbachplatz in Berlin- Wilmersdorf on. BESSY I had far-reaching scientific success in the provision of Vacuum Ultraviolet ( VUV) and soft x-ray ( XUV ). The plant was shut down for cost reasons in favor of BESSY II in 1999. Large parts of the plant were dismantled in 2001 and marketed as part of a UNESCO project to Jordan, where they are to be found in the framework of the SESAME project again using.

In BESSY I electron were stored with a kinetic energy between 200 and 800 mega-electron volts. It had a circumference of about 60 meters. With the help of BESSY I, among others, the spectrometer of the solar probe Soho and the detectors of the Space Telescope, Chandra were measured.

BESSY II

The success of BESSY I resulted in an increasing demand for synchrotron radiation, so that the decision for a more powerful beam generator, a high- brilliance radiation source, was taken.

On July 4, 1994, started the construction of BESSY II in Berlin -Adlershof, and it was inaugurated on 4 September 1998. It is a key element of the scientific and economic location Adlershof ( WISTA ). This 200 million marks (converted 102 million euros ) expensive project consists of a synchrotron with a circumference of 96 meters, as well as the actual electron storage ring with a circumference of 240 meters and an experimental hall. Today offered conditions for experiments at BESSY II at 5000 hours a year.

Will be accelerated to an energy of at most 1.7 GeV and injected into the electron storage ring. Both of deflection as well as on undulators light pulses are generated. Depending on the type of distraction ( undulator, wiggler or dipole ) photon energies can be achieved to about 15 keV. The theoretical maximum of 1.7 GeV one would only be achieved if one aligns the accelerated on this very energy electrons on a target and slows down; bremsstrahlung would then have the expected 1.7 GeV ( cf. with the operation of an X-ray tube and the Duane -Hunt 's law). The plant consumes during normal operation 2.7 MW of electrical power.

The PTB at BESSY maintains several beamlines at which both undulator as well dipolbasierte synchrotron radiation is generated and for photon metrology are used, among other things. Since the PTB using the BESSY often performs calibrations of light sources and detectors of various kinds, the BESSY II is the European radiation standard in this context. As an example may be mentioned the SOHO satellite to study the sun here the SUMER and CDS.

On 24 September 2004 a start was made in the immediate vicinity of the Metrology Light Source (MLS ), also known as Willy Wien Laboratory to build a project of the PTB. This was put into operation in the spring of 2008 and will take over tasks similar BESSY I, among others. The MLS has a circumference of 48 meters.

Research at BESSY was always in friendly cooperation with similar projects, in particular the DESY in Hamburg. Electron storage rings are very expensive and can only be realized through sustained support from public bodies.

There are different modes in which BESSY is operated. These differ in the time interval between the electron bunches:

• Multi Bunch: This is the operation mode that is most commonly used. Here, about 350 equal -filled electron bunches in the ring at a time interval of 2 ns each other. Between packets is a gap of about 100 ns is left, in which only four individual, but more filled electron bunches are (together " hybrid restorative "). These packages are used on a particular beamline to produce very short light pulses. Normally, the synchrotron Top up mode ie by continuous injection, the filling is kept constant all packages.
• Single Bunch: This operation is offered in half- year, two weeks. Here there is only a single electron bunch in the ring. This mode is suitable for time-resolved experiments, since the time interval between two successive light pulses is 800 ns, so that they can be well distinguished.
• Low- Alpha: In the low - alpha mode ( both single bunch, as well as multi Bunch ) are the electron bunches spatially highly concentrated ( with less filling), so that time- short light pulses are generated. Furthermore, the radiated intensity in the terahertz range is much greater in this mode.

Experiments at BESSY II

• X-ray absorption spectroscopy ( XAS )
• X-ray fluorescence analysis ( XRF)
• Photoelectron spectroscopy ( PES)
• X-ray emission spectroscopy ( XES )
• Photoemission electron microscopy ( PEEM )
• X-ray microscopy
• Femtoslicing
• X-ray lithography
• X-ray structural analysis of proteins
• Infrarotellipsometrie
• Infrared microscopy

BESSY -FEL

As of July 2000, the construction of a free-electron laser was (FEL ) in planning. The approximately 400 m long linear accelerator to be built right next to the synchrotron BESSY II at the Ernst- Ruska-Ufer. He should just create like the ring accelerator, the light pulses in the ultraviolet to soft X-ray range. However, these would be of higher intensity at much shorter duration. A planned area of ​​application is, for example, the study of chemical reactions, in which the complex processes can be made by the stroboscopic snapshots.

In May 2006, the Science Council has approved the construction of the BESSY -FEL recommended. From 2007 to 2010 should first be built and tested a two-stage system, which should then be expanded starting in 2010 to the four-stage BESSY -FEL.

In the autumn of 2008 it was decided not to build the FEL at BESSY II, but as an extension to FLASH at DESY in Hamburg. At BESSY II, however, the study of a linear accelerator with energy recovery ( ERL ) is to take place.