The undulating way to an X-ray laser

19 September 2001

Scientists at the DESY laboratory, Hamburg, are making progress towards an X-ray laser, planned as part of the TESLA project. TESLA is a proposal to build a 33-km long accelerator, not only for use as an electron-positron collider, but also to serve as a source of electrons for an X-ray laser, which could be used for research in many fields, from materials science to medicine. The laser being developed is a free-electron laser, which uses electrons accelerated very close to the speed of light to produce intense flashes of light. The light is emitted as the electrons follow a tight zig-zag path through many magnets in a structure known as an "undulator". In addition, the emitted light interacts with electrons ahead, and causes them to emit even more light in a process known as "self-amplified spontaneous emission" (SASE). This image shows the undulator (the yellow structure) being used in the TESLA test facility, which has recently achieved the maximum possible output at ultraviolet wavelengths (98 nm).

Credit: DESY
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