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| TUBAU01 |
FLASH Upgraded - Preparing for the European XFEL
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211 |
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Since 2005, the Free electron LASer in Hamburg, FLASH, has delivered a high brilliance photon beam to users in a wavelength range between 13 nm and 40 nm. To meet the user demands for 4 nm wavelengths, sub-50fs timing stability, and better pointing stability, the accelerator will be continuously upgraded within the next few years. The upgrade to an energy of 1.3 GeV, the transverse and longitudinal intra-train feedback system, and a 3rd harmonic cavity at 3.9 GHz are key prototype tests for the European XFEL. FLASH also serves as a test bench for an entirely new approach to accelerator facility synchronisation involving optical pulses distributed in length stabilized fibres. Increased stabilization of the electron beam peak current and its arrival time should provide the possibility to reliably seed the electron bunch with higher laser harmonics. In this paper, an overview of the planned upgrade for FLASH will be presented with respect to its usefulness for the European XFEL. The status of the XFEL project will also be briefly summarized.
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Slides
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| TUBAU02 |
Status of SCSS & X-ray FEL Project in Japan
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216 |
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- T. Shintake
RIKEN Spring-8 Harima, Hyogo
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Staus of SCSS project after the first lasing last year will be reported. The X-ray FEL, which uses 8 GeV C-band, is under construction, whose status will be reported.
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Slides
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| TUBAU03 |
STARS – an FEL to Demonstrate Cascaded HGHG
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220 |
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- M. Abo-Bakr, W. Anders, J. Bahrdt, R. Follath, K. Goldammer, S. C. Hessler, K. Holldack, T. Kamps, B. C. Kuske, A. Meseck, T. Quast, J. Knobloch
BESSY GmbH, Berlin
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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.
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Slides
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| TUBAU04 |
Towards a Low Emittance X-ray FEL at PSI
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224 |
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- A. Adelmann, A. Anghel, R. J. Bakker, M. Dehler, R. Ganter, C. Gough, S. Ivkovic, F. Jenni, C. Kraus, F. Le Pimpec, S. C. Leemann, K. B. Li, P. Ming, B. S.C. Oswald, M. Paraliev, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, T. Schietinger, V. Schlott, L. Schulz, A. Streun, F. Stulle, D. Vermeulen, F. Q. Wei, A. F. Wrulich, A. Oppelt
PSI, Villigen
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The Paul Scherrer Institute (PSI) in Switzerland aims at building a compact and cost-effective X-ray FEL facility for the wavelength range 0.1 - 10 nm. Based on the generation of very low emittance beams, it consists of a low-emittance electron gun (LEG) followed by high-gradient acceleration, and advanced accelerator technology for preserving the initial low emittance during further acceleration and bunch compression. In order to demonstrate the feasibility of the concept and the emittance preservation, a 250 MeV test facility will be built. This machine has been designed to be used as injector for the X-ray FEL at a later date. The accelerator design of the 250 MeV linac will be presented in the paper together with the status of the LEG and high gradient acceleration.
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Slides
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| TUBAU05 |
One Angstrom FEL Oscillator using ERL Beams
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- S. Reiche
UCLA, Los Angeles, California
- s. Shvydko, K.-J. Kim
ANL, Argonne, Illinois
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An oscillator X-ray FEL for 1-Å is feasible with ERLs. We have studied a 1-Å FEL using electron beams extrapolated from the "high coherence" mode of the proposed Cornell ERL, using the electron energy = 7 GeV, the undulator parameter K=1.4, and period length=1.88 cm. With a 30-m undulator the small signal gain is about 20%, sufficient for "lasing" if one round trip reflectivity is greater than 90%. The gain will be higher for a higher bunch current achievable with further optimization of the gun. The peak power of the circulating optical beam at saturation is about 20 MW and its bandwidth 10-6. The increased energy spread of the electron beam due to the FEL interaction does not pose problem for the recirculation optics. Two possible schemes for optical cavity are possible. One is a cavity of regular triangle with three crystal reflectors. Another is to use a cavity consisting of two Bragg reflectors at near-backscattering configuration and a grazing incidence mirror in between. Parasitic diffraction in backscattering of a cubic crystal provides a convenient out-coupling mechanism. The fraction of parasitic diffraction can be set to a small, desired value while keeping the high reflectivity in the main diffraction by suitably orienting the crystals away from the exact backscattering geometry. The mirror serves also the important function of focusing the x-ray beam.
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Slides
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