Uni HH, Hamburg
DESY, Hamburg
PSI, Villigen
DELTA, Dortmund
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
The Free-electron-laser at Hamburg (FLASH) operates in the Self-Amplified Spontaneous Emission (SASE) mode, delivering to users photons in the XUV wavelength range. The FEL seeding schemes promise to improve the properties of the generated radiation in terms of stability in intensity and time. Such an experiment using higher harmonics of an optical laser as a seed is currently under construction at FLASH. The installation of the XUV seeding experiment (sFLASH) is going to take place in fall 2009. This includes mounting of new variable-gap undulators upstream of the existing SASE-undulators, building the XUV-seed source as well as installation of additional photon diagnostics and electron beam instrumentation. In this contribution the layout of sFLASH will be discussed together with the technical design of its major components.
FYSIKUM, AlbaNova, Stockholm University, Stockholm
Uppsala University, Uppsala
Uni HH, Hamburg
DELTA, Dortmund
DESY, Hamburg
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
We present results from the new electron bunch diagnostic tool, Optical Replica Synthesizer [1] (ORS), installed at FLASH. The ORS produces an optical replica of the electron bunch profile, which is analyzed with a Grenouille, a device based on the Frequency Resolved Optical Gating (FROG) technique. This optical replica is generated by inducing a microbunching in the electron bunch and letting it pass through an undulator, called a radiator. The radiator emits coherently at the wavelength of microbunching, 772 nm. In order to create the microbunching a laser pulse is spatially and temporally overlapped with the electron bunch in another undulator, placed before the radiator. This introduces an electron energy modulation which is transformed into a density modulation in a chicane before the microbunched electron bunch is sent into the radiator. We observed an optical replica pulse of approximately 5 microJ corresponding to an electron bunch-spike of about 150 fs FWHM when the accelerators were set at optimal FEL conditions. We also showed that the ORS can run parasitically while maintaining SASE by steering the electron beam around the outcoupling mirror for the radiation.
[1] E. Saldin, E. Schneidmiller, M. Yurkov, “A simple method for the determination of the structure of ultrashort relativistic electron bunches,” Nucl. Inst. and Methods A 539 (2005) 499.
Uni HH, Hamburg
DESY, Hamburg
PSI, Villigen
DELTA, Dortmund
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
Starting from next year, the technical feasibility of a direct seeding scheme at 30 and 13nm will be studied at the free-electron laser FLASH at DESY. During a major shutdown in order to upgrade the SASE-FEL facility, it is planned to install a HHG source, a new chain of 10 m variable gap undulators and a dedicated commissioning beamline for photon diagnostics and pilot time-resolved pump-probe experiments. Besides demonstrating successful seeding at short wavelength, the project aims for time resolution in the 10 fs range to study ultrafast processes by combining the naturally synchronized FEL and seed laser pulses. After the extraction of the radiation in a magnetic chicane, a short branch will accommodate intensity and beam monitors and a spectrometer. The intensity monitor detects scattered photons from a gold mesh on a shot-to-shot basis using micro-channel plates and XUV diodes. It is designed to detect photons several orders of magnitude apart in flux, i.e. spanning the wide range from the spontaneous emission up to the seeded FEL radiation at gigawatt power level. Simulations of this device are presented as well as test and calibration measurements carried out at FLASH.