Using the Free-electron LASer in Hamburg (FLASH), DESY has established a new world record, generating pulses of laser light at wavelengths between 13.5 and 13.8 nm with an average power of 10 mW and energies of up to 170 µJ per pulse, all at repetition rates of 150 times a second. The pulses have a duration of only around 10 fs, so the peak power per pulse can reach 10 GW, greater than is currently available at the biggest plasma X-ray laser facilities. In addition, a specific part of the radiation at 2.7 nm – the fifth harmonic – enables FLASH to reach deep into the “water window”, a wavelength range that is crucially important for the investigation of biological samples. The range around 13.5 nm is also important because laser radiation of this wavelength is required by the semiconductor industry to produce the next generation of microprocessors using extreme ultraviolet lithography.
FLASH is currently the only laser facility that can deliver ultra-short high-power X-ray laser pulses with a very high repetition rate. It currently generates laser radiation with fundamental wavelengths between 13.1 and 40 nm. Future development will see the repetition rate reach the multi-kilohertz range and the average power increase to more than 100 mW. FLASH also produced coherent radiation at the third and fifth harmonics of the 13.7 nm fundamental wavelength, that is, at around 4.6 and 2.7 nm with a pulse duration of less than 10 fs. The corresponding energies approach 1 µJ and 10 nJ per pulse for the third and fifth harmonics, respectively.
In 2007, the facility will be upgraded to allow it to generate radiation with a fundamental wavelength that is continuously tunable between 6 and 60 nm. At the higher harmonics, FLASH will thus provide ultra-short laser pulses with microjoule energies for which the wavelengths will be tunable within and across the edges of the water window. This will create unprecedented opportunities for high-resolution in vitro 2D and 3D imaging and spectroscopy of biological systems.
The record performance was achieved by the DESY FLASH team in collaboration with international partners, the characterization of the photon beams being performed in collaboration with researchers from the Laboratoire d’interaction du rayonnement X avec la matière (CNRS/Université Paris-Sud), the International Research Centre in Experimental Physics at Queen’s University Belfast, and the National Centre for Plasma Science and Technology, Dublin City University.
