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On the way to the design electron energy of 1 GeV: replacement of accelerator modules in the FLASH tunnel during the summer shutdown 2007
Further New Possibilities for the Experiments
There is a strong scientific case for FELs producing X-rays and therefore an equally strong interest in reaching this spectral range as soon as possible. At FLASH the linear accelerator will be extended to its full energy of 1 GeV in the summer of 2007, and lasing at wavelengths close to 6 nm or photon energies near 200 eV is expected for fall 2007. Taking into account that the 3rd and 5th harmonic are only two and four orders of magnitude weaker than the fundamental, the “water window” is easily reached and time-resolved spectroscopy experiments can be performed at photon energies up to 600 eV. This enables e.g. most interesting applications in magnetization dynamics with a time resolution of 10 femtoseconds. A 20-percent increase of linac energy is among the options for further upgrades of FLASH currently under discussion.
One of the key issues at FLASH (and other FELs in the future) is to maximize the usage of the single radiation beam that it produces. Currently the FEL beam is switched to different experiments on a shift-by-shift basis in order to change the wavelength, if required, and to give one user team the chance to change samples or evaluate data while the other team uses the beam for experiments. It is intended to further increase the efficiency by faster switching of the beam, up to once a second, so that two experiments can be done quasi simultaneously; for example, one experiment makes use of single pulses for coherent imaging while the other uses a bunch train to accumulate electron and ion distributions of single atoms, molecules or ions. In the future the total user capacity of the facility could practically be doubled by building a second undulator with variable gap, including additional beamlines and experimental stations. This would allow fully parallel operation of two experiments at different wavelengths and pulse rates etc. Such possibilities are currently being investigated.
FLASH has been at the forefront of FEL development and science applications, it is supported by a strong German and international user community, and with some upgrades it will offer unique features in a spectral range that includes the water window and the L edges of the 3d transition elements and is complementary to the LCLS and other European FEL projects. Therefore, FLASH is extremely well positioned for many years, at least until the middle of the next decade.
