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| WEBAU01 |
Adaptive 3-D UV-laser Pulse Shaping System to Minimize Emittance for Photocathode RF Gun
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298 |
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- T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, A. Mizuno, S. Suzuki, T. Taniuchi, K. Yanagida, H. T. Tomizawa
JASRI/SPring-8, Hyogo-ken
- F. Matsui
Industrial Technology Center of Fukui, Fukui City
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We developed an adaptive 3-D shaping (both temporal (1D) and spatial (2D)) short pulse (80 fs~40 ps) UV-laser system as an ideal light source for yearlong stable generation of a low emittance electron beam with a high charge (1~2 nC/pulse). In its current form, the laser’s pulse-energy stability has been improved to 0.2~0.3% (rms; 10 pps, 0.4 TW in femtosecond operation) at the fundamental wavelength and 0.7~1.4% at the third-harmonic generation. Such improvement reflects an ability to stabilize the laser system in a humidity-controlled clean room. The pulse-energy stability of a mode-locked femtosecond oscillator has been continuously held to 0.3% (p-p) for 10 months, 24 hours a day. In addition, the ideal spatial and temporal profiles of a shot-by-shot single UV-laser pulse are essential to suppress emittance growth in an RF gun. We apply a deformable mirror that automatically shapes the spatial UV-laser profile with a feedback routine, based on a genetic algorithm, and a pulse stacker for temporal shaping at the same time. The 3D shape of the laser pulse is spatially top-hat (flattop) and temporally a square stacked pulse. Using a 3D-shaped laser pulse with a diameter of 0.8 mm on the cathode and pulse duration of 10 ps (FWHM), we obtain a minimum normalized emittance of 1.4 π mm mrad with beam energy of 26 MeV.
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| WEBAU02 |
Recent Experimental Results from PITZ
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- G. Asova, K. Boyanov
INRNE, Sofia
- J. W. Baehr, C. H. Boulware, H.-J. Grabosch, M. Hänel, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, S. Lederer, A. Oppelt, B. Petrosyan, S. Riemann, S. Rimjaem, T. A. Scholz, L. Staykov, F. Stephan
DESY Zeuthen, Zeuthen
- K. Floettmann
DESY, Hamburg
- L. H. Hakobyan
YerPhI, Yerevan
- R. Richter
BESSY GmbH, Berlin
- J. Roensch
Uni HH, Hamburg
- A. Shapovalov
MEPhI, Moscow
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The Photo Injector Test facility at DESY in Zeuthen (PITZ) was built to develop and optimize electron sources for superconducting linac driven, high power, short wavelength FELs. A 1.5 cell L-band gun cavity characterized at PITZ has provided beam for FLASH since 2004. A spare RF gun has been characterized at PITZ and delivered to Hamburg as well. To meet the stringent requirements on beam quality for the European XFEL, a substantial upgrade program is ongoing at PITZ. In a first operation period during October 2006, projected normalized transverse emittances in both transverse planes between 1.2 and 1.5 mm mrad for a bunch charge of 1 nC were measured. These results are in good agreement with simulations. A major step towards even lower emittance is the increase of the electric field at the photo cathode from 40 MV/m to 60 MV/m. With the upgrades ongoing now, simulations predict a projected normalized transverse emittance of 1.2 mm mrad and better for 1 nC bunch charge in the running period scheduled for summer 2007. This contribution will give an overview of the experimental results obtained at PITZ in the operation periods of October 2006 and summer 2007 (e.g. transverse and longitudinal phase space measurements, dark current and cathode properties). The main steps of the further upgrade program at PITZ will be mentioned as well.
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| WEBAU03 |
Performance Tests of the Photon Monochromator for Self-seeding at FLASH
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306 |
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- H. K. Bechtold, J. Hartvig, H. Juul, V. Toft
Aarhus University, Aarhus
- R. Follath, G. Reichardt, F. Senf, F. Siewert
BESSY GmbH, Berlin
- U. Hahn, J. Viefhaus, R. Treusch
DESY, Hamburg
- S. V. Hoffmann
ISA, Aarhus
- Ch. Knoechel
LBNL, Berkeley, California
- R. Reininger
UW-Madison/SRC, Madison, Wisconsin
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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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| WEBAU04 |
Single-Shot Longitudinal Bunch Profile Measurements at FLASH Using Electro-Optic Detection: Experiment, Simulation, and Validation
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310 |
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- V. R. Arsov, E.-A. Knabbe, B. Schmidt, P. Schmüser, B. Steffen
DESY, Hamburg
- G. Berden, A. F.G. van der Meer
FOM Rijnhuizen, Nieuwegein
- W. A. Gillespie, P. J. Phillips
University of Dundee, Nethergate, Dundee, Scotland
- S. P. Jamison
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- A. MacLeod
UAD, Dundee
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At the superconducting linac of FLASH at DESY, we have installed an electro-optic experiment for single shot, non-destructive measurements of the longitudinal electric charge distribution of individual electron bunches. The profile of the electric bunch field is electro-optically encoded onto a stretched Ti:Sa laser pulse. In the decoding step, the profile is retrieved from a cross-correlation of the encoded pulse with a 35 fs laser pulse, obtained from the same laser. At FLASH, sub-100 fs electron bunches have been measured during FEL operation with a resolution of better than 50 fs. The electro-optic encoding process in gallium phosphide as well as the decoding step in a frequency doubling BBO crystal were numerically simulated using bunch shapes simultaneously measured with a transverse-deflecting rf structure as input data. In this contribution, we present electro-optically measured profiles and compare them with the simulation.
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| WEBAU05 |
Magnetic Measurements, Tuning and Fiducialization of LCLS Undulators at SLAC
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- V. Kaplounenko, A. W. Weidemann, Z. R. Wolf, Yu. I. Levashov
SLAC, Menlo Park, California
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A new Magnetic Measurement Facility (MMF) has been built at Stanford Linear Accelerator Center (SLAC) to measure, tune and fiducialize undulators for Linac Coherent Light Source (LCLS) project. Climate controlled MMF utilizes two magnetic measurement benches and a large Coordinate Measurement Machine (CMM) and provides a throughput of one undulator segment a week. Magnetic measurement, tuning and fiducialization process is being presented and first tuning results are discussed.
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