FLASH is a small version of the European XFEL which is already producing laser flashes for science. The facilities differ mainly in the wavelengths of the generated light flashes.
FLASH is a free-electron laser at DESY which was commissioned in 2004 and has been used for research with shortwave ultraviolet and soft X-ray radiation since 2005. The facility is 260 metres long and generates soft X-ray radiation down to a wavelength of six nanometres (billionths of a metre). Until 2009, FLASH was the only free-electron laser in the world to produce radiation in the soft X-ray region.
The design of FLASH is identical to the European XFEL. It consists of a series of sequentially connected superconducting accelerator elements that bring the electrons to an energy of one billion electron volts. At that point, the electron beam speeds through a 30-metre-long undulator, in which radiation is generated according to the SASE principle of self-amplification. The intense light flashes are then distributed among a total of five experiment stations, where they are available to researchers for their experiments.
Besides being used for research with the generated radiation, FLASH also serves as a pilot facility for the European XFEL. Its operation provides major insights that will benefit the European XFEL, which will generate even shorter wavelengths down to one-tenth of a nanometre. At the same time, scientists and engineers can use the FLASH facility to continue development work for the planned International Linear Collider ILC for particle physics.
The facility was first called VUV-FEL (Vacuum Ultraviolet Free-Electron Laser). It was renamed FLASH (Free-Electron Laser in Hamburg) in April 2006. It was realized as an extension of the 100-metre-long TESLA Test Facility.
Science at FLASH
FLASH was the world’s first source of laserlike (coherent) shortwave ultraviolet radiation. It boasts an extremely high peak brilliance and ultrashort light pulses. The scientific interest is correspondingly great: Already for the first measuring period (August 2005 to March 2006), around 200 scientists from nine countries submitted a total of 30 project proposals for experiments in fields as diverse as cluster physics, solid-state physics, surface physics, plasma research and molecular biology.
In particular, until 2009, FLASH was the world’s only radiation source to permit proof-of-principle studies of new experimental methods for future X-ray lasers. One major breakthrough was realized already in one of the very first experiments at FLASH. The scientists achieved a world first by taking a high-resolution diffraction image of a non-crystalline sample with a single laser shot. This suggests that in the near future images from nanoparticles and even large individual macromolecules – viruses or cells – may be obtained using a single ultrashort high-intensity laser pulse, without the need for crystallizing the samples first.
You can read more about FLASH here.