| Paper | Title | Page |
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| TUBAU03 | STARS – an FEL to Demonstrate Cascaded HGHG | 220 |
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| BESSY plans to build the BESSY Soft X-ray FEL facility, a second generation FEL for the VUV and soft x-ray range. The TDR was evaluated by the German Science Council and recommended for funding subject to the condition that cascaded high-gain harmonic generation (HGHG) be demonstrated beforehand. To this end, BESSY is proposing the demonstration facility STARS for a two-stage HGHG FEL. For efficient lasing from 40 nm to 70 nm, a 325 MeV driver linac is required. It consists of a normal-conducting gun, superconducting TESLA-type modules modified for CW operation and a bunch compressor. The two-stage HGHG cascade employs variable gap undulators, with the final amplifier being an APPLE-III device for full polarization control. A beamline with user experiment completes STARS, which is planned to remain operational even after the BESSY FEL comes online. This paper summarizes the layout of STARS, the main parameters and the expected performance. | ||
| WEBAU03 | Performance Tests of the Photon Monochromator for Self-seeding at FLASH | 306 |
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A single pass FEL amplifier can produce extremely intense and fully coherent radiation at short wavelengths if it is seeded by a coherent light beam resonant with the magnetic structure and collinear with the electron beam. Since at the present time a single pass SASE FEL is the only source of sufficiently intense, tunable radiation in the soft X-ray region, it has been proposed to use such a source in combination with a narrow-band monochromator for seeding an FEL amplifier*. By means of such a "Self-Seeding", the soft X-ray free electron laser FLASH at DESY will be modified so that it can provide coherent radiation in space and time in a wavelength range from about 60-6nm (~20-200eV). In this presentation, we will focus on the performance of the photon monochromator beamline which was setup and tested at the synchrotron radiation storage ring ASTRID in Aarhus, Denmark. The optical, mechanical and vacuum design will be described along with results on the resolving power of the monochromator which have been obtained scanning across rare gas resonance lines at various energies. Based on these results we will conclude that the monochromator is mechanically very stable and reproducible and behaves according to its specifications with resolving powers between 10000 and 20000, i.e. bandwidths of a few meV only.
* J. Feldhaus, E. L. Saldin, J. R. Schneider, E. A. Schneidmiller, and M. V. Yurkov, Opt. Commun. 140, 341 (1997) |
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