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World Record at FLASH in Hamburg07.09.2006 - (idw) Deutsches Elektronen-Synchrotron DESY
The 260-meter-long free-electron laser at DESY in Hamburg delivers highest power at shortest wavelengths and reaches water window.
In the worldwide competition towards the highest laser power at the shortest wavelengths, the FLASH facility at the DESY research center in Hamburg established a new world record. In operation, the free-electron laser generated laser light flashes at wavelengths between 13.5 and 13.8 nanometers with an average power of 10 milliwatts and record energies of up to 170 microjoules per pulse - and this at repetition rates of 150 times per second. Since the pulses have a duration of only around 10 femtoseconds, the peak power per pulse can reach 10 gigawatts. These powers are larger than is currently available at even the biggest plasma X-ray laser facilities worldwide. At 2.7 nanometers a specific part of the radiation, the so-called fifth harmonic, enables FLASH to reach deep into the water window - a wavelength range that is crucially important for the investigation of biological samples.
"FLASH is currently the only laser facility in the world to deliver ultra-short high-power laser flashes in the X-ray range with a very high repetition rate," said DESY Research Director Professor Jochen R. Schneider. "FLASH thus opens up completely new experimental opportunities for researchers from nearly all the natural sciences, even within the so-called water window between 2.3 and 4.4 nanometers. In this wavelength range, the carbon atoms in organic matter absorb radiation very well, whereas the water environment remains invisible. This enables investigations that have not been feasible so far, for instance single shot holographic imaging of cellular systems in their natural in vitro environments." The range around 13.5 nanometers is also critically important because laser radiation of this wavelength is required by the semiconductor industry to produce the next generation of microprocessors using EUV lithography.
The free-electron laser FLASH, which has been available for research since August 2005, currently generates laser radiation with fundamental wavelengths between 13.1 and 40 nanometers. At wavelengths from 13.5 to 13.8 nanometers, the average energy per pulse was up to 70 microjoules at an unprecedented repetition rate of 150 pulses per second, so that the average power was in excess of 10 milliwatts. Future development of FLASH will see the repetition rate reach the multi-kHz range and the average power concomitantly increase to more than 100 milliwatts. Simultaneously, FLASH also produced coherent radiation at the 3rd and 5th harmonics of the 13.7 nanometer fundamental wavelength, i.e. at around 4.6 and 2.7 nanometers with less than 10-femtosecond pulse duration. The corresponding pulse energies approached 1 microjoule and 10 nanojoule per pulse for the 3rd and 5th harmonics, respectively.
In 2007, FLASH will undergo an upgrade that will allow it to generate radiation with a fundamental wavelength that is continuously tunable between 6 and 60 nanometers. At the higher harmonics, FLASH will thus provide ultra-short laser pulses with microjoule energies whose wavelengths will be tunable within and across the edges of the water window. This will open up unprecedented opportunities for high-resolution in vitro 2D and 3D imaging and spectroscopy of biological systems.
FLASH is the worldwide only free-electron laser facility for extreme ultraviolet and soft X-ray radiation. Around 200 scientists from 60 institutes in 11 countries use the intense laser light at currently four experimental stations for their experiments. Many further projects in various areas of physics, chemistry or molecular biology have already been proposed. The FLASH facility also plays an important pioneering role for future free-electron laser facilities that will generate laser flashes of even shorter wavelengths. Among these will be the 3.4-kilometer-long European X-ray free-electron laser XFEL, whose realization is currently being prepared at DESY in international cooperation, and which should take up operation in 2013.
The FLASH record performance has been achieved by the DESY FLASH team in collaboration with international partners, the characterization of the photon beams was performed in collaboration with researchers from LIXAM (CNRS/Université Paris-Sud), the IRCEP (Queen's University Belfast) and the NCPST (Dublin City University).
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