Free-electron laser FLASH

FLASH is a free-electron laser at DESY which was commissioned in 2004 and has been used for experiments with short-wavelength ultraviolet radiation and soft X-rays since 2005. The 260-metre-long facility is the world’s first light source to deliver laser radiation in the soft X-ray range with high peak brilliance and ultra-short light pulses – and it does so at 6 nanometres (billionths of a metre), the shortest wavelength achieved so far with a free-electron laser. FLASH will remain unrivalled worldwide until the LCLS X-ray laser starts up in California in 2009.

Initial usage of FLASH has already resulted in some spectacular new experiments, and the scientific interest is correspondingly intense. As a user facility, FLASH offers five experimental stations where different instruments can be set up as required.

Free-electron laser in Hamburg

The facility was first called VUV-FEL (Vacuum Ultraviolet Free-Electron Laser). It was renamed FLASH (Free-Electron Laser in Hamburg) in April 2006. FLASH is based on a test facility constructed in 1997 for the TESLA linear collider project. This TESLA Test Facility was extended from its original length of 100 metres to approximately 260 metres in 2003.

The facility comprises a linear accelerator with sequentially connected superconducting accelerator elements that bring the electrons to an energy of one billion electronvolts (1 GeV). At that point, the electron beam speeds through a 30-metre-long undulator, in which it generates radiation according to the SASE principle of self-amplification. The intense light flashes are then distributed among a total of five experimental stations, where they are available to researchers for their experiments.

Test facility for X-ray laser and linear collider

Besides being used for research with the generated radiation, FLASH continues to serve as a test facility – both for the European XFEL, an X-ray free-electron laser currently under construction in Hamburg which will generate even shorter wavelengths down to one-tenth of a nanometre, and for a possible future linear accelerator for particle physics, the International Linear Collider ILC. The linear accelerators of FLASH, European XFEL and ILC all rely on the superconducting technology developed by DESY and its international partners within the TESLA project. This superconducting accelerator technology and other components required for the X-ray laser European XFEL and the linear collider ILC can be further developed and tested at the FLASH facility.

Facts and figures

FLASH

- Free-electron laser with superconducting linear accelerator in TESLA technology
- Total length: 260 metres
- Generates extremely brilliant laser radiation in the vacuum ultraviolet (VUV) and the soft X-ray range using the SASE principle (wavelengths tunable between 6 and 60 nanometres)
- In user operation since 2005
- Five experimental stations