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Title |
Page |
| MOPPH034 |
Mirror Aberrations in Low Gain FEL Oscillators
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63 |
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- P. J.M. van der Slot, K.-J. Boller, R. van der Meer
Mesa+, Enschede
- H. Freund
SAIC, McLean
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To generate radiation with high spatio-temporal quality in FELs, oscillators are to be used whch are based on the combination of low gain with a large number of roundtrips in a low-loss optical resonator. Clearly, in this situation any additional loss or aberration may seriously degrade the performance and beam quality, and this becomes extremely important for high average power FEL oscillators such as the JLAB system*. Nevertheless, so far no systematic study has been made how various mirror aberrations affect the performance of such low gain FEL oscillators. Here we present the first results of such a study. Ths approach is based on the optical propagation code OPC** with the Genesis 1.3*** gain code.
* SV Benson et.al. Nucl. Instr. and Meth. A483, 434 (2002).
** JG Karssenberg, et.al. J. Appl. Phys. 100, 093106 (2006).
*** http://pbpl.physics.ucla.edu/~reiche/
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| TUPPH002 |
The Photonic FEL: Toward a Handheld THz FEL
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231 |
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- P. J.M. van der Slot, K.-J. Boller, T. Denis
Mesa+, Enschede
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Low energy, slow wave, electron beam based radiation devices, like travelling wave tubes and Cerenkov free-electron lasers, have the disadvantage that the gain seriously degrades when the operating frequency is upscaled from microwave to teraHertz frequencies. Here we propose to obtain a successful scaling with what may be called a photonic free-electron laser (pFEL). In our approach, a photonic structure serves for phase matching the radiation field to a set of copropagating electron beams. This follows an earlier suggestion based on distributed feedback*. The photonic structure additionally provides transverse coupling between the individual electron beams, such that phase locking through the interaction with the radiation field leads to the generation of transversly coherent radiation. This phase locking mechanism allows power scaling by extending the number of parallel beams propagating through the structure. We expect to be able to produce Watt-level output at THz frequencies from a handheld device and will present the basic ideas behind this concept.
* V. G. Baryshevsky, K. G. Batrakov. Nucl. Instr. and Meth. A507, 35 (2003).
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| TUAAU05 |
Design of the Nijmegen High-Resolution THz-FEL
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200 |
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- R. T. Jongma
Radboud University Nijmegen, Institute of Molecules and Materials, Nijmegen
- K. Dunkel, C. Piel
ACCEL, Bergisch Gladbach
- U. Lehnert, P. Michel, R. Wuensch
FZD, Dresden
- C. A.J. van der Geer
Pulsar Physics, Eindhoven
- A. F.G. van der Meer
FOM Rijnhuizen, Nieuwegein
- P. J.M. van der Slot
Twente University, Laser Physics and Non-Linear Optics Group, Enschede
- W. J. van der Zande
Institute for Molecules and Materials, Radboud University Nijmegen, Nijmegen
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In 2006, the Radboud University in Nijmegen received funding via the Netherlands NWO-BIG program to realize a THz laser system and a 45 T hybrid magnet system. The specifications of the THz FEL system are geared towards material science at high (30-45 T) magnetic fields (saturation spectroscopy and pulse-echo experiments), and applications e.g. in the field of biomolecular spectroscopy. A study performed during the last year demonstrated the feasibility of a THz FEL that will cover the 100-1500 micron spectral range and that operates in either a “spectroscopic mode” providing 100 Watt bandwidth limited pulses of several microsecond (spectral resolution better than 100000/1) or pump-probe pulsed mode providing macropulses with 3 GHz. micropulses. Technical challenges are in the 3 GHz operation of the source, and the narrowband operation. The latter will be obtained by filtering a single mode out of the frequency comb, realized by ensuring full coherence between the micropulses. Coherence is imposed by the stability of the electron beamμpulses (“spontaneous” coherence) or by the use of an intra-cavity (Fox-Smith) interferometer. We will present details of the chosen design.
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Slides
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| TUPPH087 |
Real-Time Ellipsometry for Monitoring the Growth of Cesium-Telluride Photocathodes
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448 |
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- P. J.M. van der Slot, K.-J. Boller, R. A. Loch, M. J.H. Luttikhof, L. G. Prodan, M. Tesselaar
Mesa+, Enschede
- J. W.J. Verschuur
Twente University, Laser Physics and Non-Linear Optics Group, Enschede
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Semiconductor photocathodes, especially Cesium-Telluride photocathodes, are vital for generation of high brightness electron beams used in free-electron lasers. However the quantum efficiency and lifetime depends critically on manufacturing and operational conditions. Monitoring the formation of the photocathode is essential for understanding these dependencies. For example, the deposition rate of the Cs correlates to the quantum efficiency and adversely correlates to the lifetime. We will discuss the use of ellipsometry for monitoring the formation of the photocathode, describe our experimental configuration and discuss preliminary results obtained with CsTe photocathodes. These results seems to indicate that ellipsometry is a viable method for monitoring the formation of CsTe photocathodes.
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