Bahrdt, J.

Paper	Title	Page
MOPPH050	The Properties of the FEL Output for Different Seeding Schemes	150
	J. Bahrdt BESSY GmbH, Berlin B. Faatz, R. Treusch DESY, Hamburg V. Miltchev Uni HH, Hamburg R. Reininger New Affiliation Request Pending, -TBS-
	Several seeding schemes, like self seeding for FLASH or seeded HGHG cascades for BESSY soft X-ray FEL, are proposed for existing or planned free electron laser facilities. The simulation of these schemes requires the detailed knowledge of the properties of the seeding radiation and the implementation of these properties in the Codes. Time dependent simulations with the 3D code GENESIS calculate the electric field distribution in and at the end of the undulator. The physical optics code PHASE permits the propagation of wave fronts across grazing incidence optics. Using the combination GENESIS PHASE GENESIS, the properties of the FEL output for different seeding schemes can be obtained. For example, the radiation quality of a SASE FEL can be improved in a self seeding scheme. Here, the radiation is monochromatized after a first undulator section and reflected back to the second Undulator modules. We present simulation studies for the self seeding option of FLASH.
MOPPH061	The Test Facility for Harmonic Generation at the MAX-lab Injector Linac	182
	S. Werin, M. Brandin, T. Hansen, S. Thorin MAX-lab, Lund M. Abo-Bakr, J. Bahrdt, K. Goldammer BESSY GmbH, Berlin A. L'Huillier, J. Larsson, A. Persson, C.-G. Wahlstrom New Affiliation Request Pending, -TBS-
	The MAX-lab injector linac system will be used in a test set-up for developing and testing techniques important for the designs of the BESSY FEL and the MAX IV FEL proposals. The first goal is using a 400 MeV electron beam to generate third harmonic photons at 90 nm from a 266 nm seed laser. The installations at MAX-lab are being improved by a new photo cathode RF gun (to improve emittance and peak current), an optical klystron (2 undulators + chicane, supplied by BESSY) and a combined synchronised laser system for both the RF-gun and the seeding system. The injector optics and transport system are also being retuned to allow the necessary electron beam compression. The project is a part of the EUROFEL collaboration.
THBAU01	APPLE Undulators for HGHG-FELs	521
	J. Bahrdt BESSY GmbH, Berlin
	Cascaded HGHG-FEL facilities have been proposed by several groups. In these machines the beam characteristics of the initial seeding laser like short pulses and a small bandwidth are transformed to shorter wavelengths where lasers are not available. The first stages are equipped with planar devices. For full polarization control the last amplifier and the final radiator can be realized as APPLE devices. The specific demands on the polarizing devices as compared to planar hybrid devices are discussed for the example of the proposed BESSY HE-FEL to be operated at 1nm: the small good field region implies tight geometrical tolerances. Gap and phase dependent focussing effects have to be compensated. The field optimization procedure requires specific strategies. An improvement of the magnetic material is helpful in this context. Other important issues are the radiation protection system and the complexity of the control system.
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