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| TUPPH064 | A Mechanical Shutter to Select Single Bunch Trains at the FLASH Facility at DESY | 470 |
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A fast, mechanical shutter to select single bunch trains at the FLASH-Facility* at DESY Hamburg is described. This facility is relying on superconducting accelerator modules, which are operated to accelerate bunch-trains with a repetition rate of up to 10 Hz**. This time interval of down to 100ms makes it possible for FEL users to use a mechanical system to select single bunch-trains for sample excitation. The described system is based on a slot-winding cylinder, moving a carbon shutter blade forward and backward while rotating. A commercial electronics (PLC) is used to steer a servo system based on an electronically commutated (EC) low-voltage motor. To select a bunch-train, the motor is started at the time when one train passes the station. During the following 100ms, the cylinder is turned by 180°, leading to a movement of the shutter by 48mm to the fully open position, thus allowing the passage of the following bunch-train. During the next 100ms the rotation is continued to the 360° position, thus blocking the next bunch-train by pushing the shutter back to the fully closed position. The concept, realization, system-tests and first operational experiences are presented.
* Free electron LASer in Hamburg** V. Ayvazyan et al., "First operation of a Free-Electron Laser generating GW power radiation at 32 nm wavelength", Eur. Phys. J. D 37, (2006), 297-303 |
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| FRAAU03 | Wave-Front Observations at FLASH | 794 |
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| During the first user operation of the Free-Electron Laser in Hamburg (FLASH) wavefront measurements have been recorded in the vacuum-ultraviolet region using a Hartmann sensor (by Imagine Optic). The Hartmann principle is based on a pinhole array, which divides the incoming beam into a large number of sub-rays monitored in intensity and position of individual spots. The identification of the local slope of the incident wavefront makes the aberrations from a perfect spherical wavefront visible. Ray tracing in upstream direction accesses the beam focal point in size and position. The intense and coherent vacuum-ultraviolet FEL beam leads to unique requirements for the wavefront sensor setup. We report an optimized setup to observe the metrology of flat and curved mirrors at FLASH beamlines. The effects of solid and gaseous filters are selectively described in the wavelength regime of 10nm to 32nm. The use of wavefront measurements to provide reliable machine parameter is discussed. The wavefront sensor proved to be a valuable tool to observe the FEL beam quality and the performance of optical elements, filters and diagnostic tools. | ||
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