Wuensch, R.

Paper	Title	Page
TUPPH014	Laser Gain and Intra-Cavity Losses of the ELBE Mid-IR FEL	339
	U. Lehnert, P. Michel, W. Seidel, J. Teichert, R. Wuensch FZR, Dresden
	The the U27-FEL of the ELBE radiation source allows to choose between five mirrors with different outcoupling holes. This allows to adapt the optical resonator to the required wavelength range to ensure the needed laser gain and to optimize the outcoupled laser power. Another parameter which influences the achievable laser gain and output power is the detuning length of the optical cavity. While for CW operation often the minimum detuning point is choosen which maximizes the outcoupled power, for pulsed-mode operation about one wavelength of cavity detuning maximizes the laser gain and yields best stability of the laser. To gain some insight into the behavior of the optical resonator we have measured the round-trip losses and the net laser gain and compare both to calulations. For the measurements we have used a fast-readout MCT detector to measure the decay and rise-time of the outcoupled infrared beam caused by a 10μs break in the electron beam micro-pulse train. We show gain and loss for 5, 10 and 20μm wavelength with the typical detuning curves of an FEL.
TUPPH016	The Partial-Waveguide Resonator of the U100-FEL at FZ Rossendorf	345
	R. Wuensch, M. Freitag, R. Schlenk, W. Seidel, U. Willkommen, D. Wohlfarth, B. Wustmann FZR, Dresden
	The U100-FEL, which is under construction at the Forschungszentrum Rossendorf, will be equipped with a parallel-plate waveguide which is 10 mm high (inside), almost 8 m long and covers more than two third of the total resonator length. Its horizontal width varies from 70 mm within the undulator up to 130 mm at the downstream resonator mirror. A special diagnostics had to be developed to align the electron and the IR beam within this waveguide. A drive system has been designed for the cylindrical downstream resonator mirror. It allows to shift and tilt the mirror, which is completely embedded in the waveguide. The size and the curvature of the bifocal upstream resonator mirror has been fitted to minimize the optical loss in the resonator. To adjust the outcoupling to the varying beam size on the mirror surface a set of three collocated, relocatable mirrors with different outcoupling hole sizes will be applied. We present various sophisticated design concepts which comply with the large wavelength range and the special requirements caused by the bulky waveguide construction and its small free space in vertical direction.
TUCAU02	The Rossendorf IR-FEL ELBE	488
	P. Michel, H. Buettig, F. G. Gabriel, M. Helm, U. Lehnert, Ch. Schneider, R. Schurig, W. Seidel, D. Stehr, J. Teichert, S. Winnerl, R. Wuensch FZR, Dresden
	The radiation source ELBE is the central research facility in the Forschungszentrum Rossendorf. The machine is based on a 40 MeV superconducting RF Linac wich can be operated up to 1 mA in cw mode. After commissioning the Bremsstrahlung and the X-ray facilities in 2002, and 2003 respectively, and the first lasing of the mid-IR FEL (4-22 um) in 2004 about 7000 hours user beam-time have been provided. At present a second FEL for long IR waves (15-150 um) using a partial waveguide is under commissioning. Besides in-house users especially the IR beam is available to external users in the FELBE (FEL@ELBE) program witch is a part of the integrated activity on synchrotron and free electron laser science in the EU. In this talk the fundamental features of the ELBE IR FEL's and the parameters demanded by users are displayed. In addition, an overview about user experimental work and important machine date like availability are shown. Future projects like the combination of the new High Magnetic Field lab with the ELBE-IR beams will be described.
	Slides
	Talk