| Paper |
Title |
Page |
| MOPC028 |
Experimental Layout of 30 nm High Harmonic Laser Seeding at FLASH
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127 |
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- H. Schlarb, S. Düsterer, J. Feldhaus, T. Laarmann
DESY, Hamburg
- A. Azima, J. Boedewadt, H. Delsim-Hashemi, M. Drescher, S. Khan, Th. Maltezopoulos, V. Miltchev, M. Mittenzwey, J. Rossbach, R. Tarkeshian, M. Wieland
Uni HH, Hamburg
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Since 2004, the free-electron laser FLASH at DESY has operated in the Self-Amplified Stimulated Emission mode, delivering to users photon beams with wavelengths between 6.5 nm and 40 nm. In 2009, DESY plans to install a 3.9 GHz RF acceleration section for the production of electron bunches with high peak currents (~kA), but ten times larger pulse durations (~250 fs) compared to the present configuration. The relaxed timing requirements of the new configuration make it possible to externally seed FLASH with high harmonics of an optical laser (sFLASH). The aim of the project is to study the technical feasibility of seeding an FEL at 30 nm with a stability suited for user operation. sFLASH will use 10 m of gap-tunable undulators installed in front of the fixed gap SASE-undulator. A chicane behind the seeding undulators will allow to extract the output radiation for a careful characterisation and for first pump-probe experiments with a resolution in the 10 fs range by combining FEL and seed laser pulses.
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| TUPC081 |
Single-shot Longitudinal Bunch Profile Measurements at FLASH Using Electro-optic Detection Techniques
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1242 |
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- P. J. Phillips, W. A. Gillespie
University of Dundee, Nethergate, Dundee, Scotland
- V. R. Arsov, H. Schlarb, B. Schmidt, P. Schmüser
DESY, Hamburg
- G. Berden, A. F.G. van der Meer
FOM Rijnhuizen, Nieuwegein
- S. P. Jamison
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- A. MacLeod
UAD, Dundee
- B. Steffen
PSI, Villigen
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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 electron bunch field is electro-optically encoded onto a streched Ti:Sa laser pulse. In the decoding step, the profile is retrieved from a spectral measurement of the encoded pulse or 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 measurements have been validated with a tranverse deflecting cavity measurements.
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| TUPC135 |
Experimental Determination of the Timing Stability of the Optical Synchronization System at FLASH
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1386 |
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- F. Loehl, V. R. Arsov, M. Felber, K. E. Hacker, B. Lorbeer, F. Ludwig, K.-H. Matthiesen, H. Schlarb, B. Schmidt
DESY, Hamburg
- S. Schulz, A. Winter, J. Zemella
Uni HH, Hamburg
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An optical, drift free synchronization system with a stability of better than 10 fs is presently being installed at the free electron laser FLASH. A periodic laser pulse train from a mode-locked, erbium doped fiber laser is distributed via length stabilized fiber links. In this paper, we present measurements of the timing stability of the optical distribution system. Two arrival time monitors (BAM) are used to measure the electron bunch arrival times at two positions in the linac separated by 60 m. Each BAM is supplied with fiber-laser pulses by its own fiber link. By correlating the measured arrival times of the same electron bunches, the overall performance of the optical distribution system and the BAMs can be evaluated. A resolution and timing stability of better than 30 fs has beed reached.
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| TUPC114 |
Results from the Optical Replica Experiments in FLASH
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1332 |
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- V. G. Ziemann, G. Angelova
UU/ISV, Uppsala
- J. Boedewadt, S. Khan, A. Winter
Uni HH, Hamburg
- M. Hamberg, M. Larsson, P. M. Salen, P. van der Meulen
FYSIKUM, AlbaNova, Stockholm University, Stockholm
- F. Loehl, E. Saldin, H. Schlarb, E. Schneidmiller, M. V. Yurkov
DESY, Hamburg
- A. Meseck
BESSY GmbH, Berlin
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We present experimental results from the optical replica synthesizer, a novel device to diagnose sub-ps electron bunches by creating a coherent optical pulse in the infrared that has the envelope of the electron bunch and analyzing the latter by frequency resolved optical gating methods. Such a device was recently installed in FLASH at DESY. During an experiment period the spatial and temporal overlap of a several ps long electron bunch and a 200 fs laser pulse were achieved within an undulator. Coherent transition radiation due to the induced micro-bunching was observed on a silver-coated silicon screen and varying the timing between electrons and laser pulse produced two-dimensional images of the slices as a function of the longitudinal position within the electron bunch. In a second experiment the strongly compressed electron bunch is modulated by a laser pulse lengthened to about 2 ps and replica pulses that are emitted from a second undulator are observed and diagnosed by frequency resolved optical gating methods.
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| THPC152 |
Electro-optic Bunch Arrival Time Measurement at FLASH
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3348 |
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- V. R. Arsov, M. Felber, E.-A. Knabbe, F. Loehl, B. Lorbeer, F. Ludwig, K.-H. Matthiesen, H. Schlarb, B. Schmidt, P. Schmüser, S. Schulz, B. Steffen, A. Winter, J. Zemella
DESY, Hamburg
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The operation of the next generation free electron lasers such as FLASH and the planned European XFEL requires drift free synchronization and femto-second stability. For this purpose an optical synchronization system has been developed, based on a mode-locked erbium-doped fiber laser, whose pulses are distributed over length stabilized fiber links. In order to evaluate the performance of the optical distribution system and the bunch arrival time monitors (BAM) an independent reference is needed. The measurement of the electro-optic (EO) response in a GaP crystal offers such a possibility. The method is destruction free and allows simultaneous determination of the peak current and the charge center of mass arrival time with femto-second precision. The measurements are performed with a 0.175 mm thick GaP crystal using 3 ps linearly chirped pulses from a Ti:Sa oscillator. The EO signal is encoded to the chirped pulse and spectrally resolved near crossed polarizers. Comparison of the EO and BAM timings provides a check of the relative accuracy of both methods, including the accuracy of the optical timing distribution system.
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| THPC158 |
Measurement and Stabilization of the Bunch Arrival Time at FLASH
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3360 |
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- F. Loehl, V. R. Arsov, M. Felber, K. E. Hacker, B. Lorbeer, F. Ludwig, K.-H. Matthiesen, H. Schlarb, B. Schmidt
DESY, Hamburg
- W. Jalmuzna
TUL-DMCS, Łódź
- S. Schulz, A. Winter, J. Zemella
Uni HH, Hamburg
- J. Szewinski
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
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To fully exploit the experimental opportunities offered by the 10 - 30 fs long light pulses from FLASH, e.g. in pump-probe experiments, precise measurements and control of the electron-bunch arrival-time on the 10 fs scale are needed. A bunch arrival time monitor (BAM) which uses the optical synchronization system of FLASH as a reference has been developed for this purpose. The bunch induced signal from a GHz-bandwidth beam pick-up is guided into an electro-optical modulator in which the periodic laser pulse train of the optical synchronization system experiences an amplitude modulation. Detection of this modulation allows to determine the bunch arrival time with a resolution of better than 20 fs. The superconducting linac of FLASH generates trains of up to 800 bunches. The BAM signals can be used for an intra-bunch train feedback stabilizing the arrival time to better than 50 fs. The feedback is capable of generating well-defined arrival time patterns within a bunch train which are useful for overlap-scans in pump-probe experiments. First results from the feedback installed at FLASH will be presented.
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| THPC160 |
An Optical Cross-correlation Scheme to Synchronize Distributed Laser Systems at FLASH
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3366 |
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- S. Schulz, V. R. Arsov, M. Felber, F. Loehl, B. Lorbeer, F. Ludwig, K.-H. Matthiesen, H. Schlarb, B. Schmidt, A. Winter
DESY, Hamburg
- P. Schmüser, J. Zemella
Uni HH, Hamburg
- B. Steffen
PSI, Villigen
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The soft X-ray free-electron laser FLASH and the planned European XFEL generate X-ray light pulses in the femto-second range. For time-resolved pump-probe experiments, future operation modes by means of laser seeding and for special diagnostic measurements it is crucial to synchronize various laser systems to the electron beam with an accuracy better than 30 fs. For this purpose an optical synchronization system at the telecommunication wavelength of 1550 nm is currently being installed and tested at FLASH. We developed a background-free optical cross-correlation scheme to synchronize two mode-locked laser systems of different center wavelengths and repetition rates with an accuracy better than 10 fs. The scheme was tested by linking a commercial 81 MHz Ti:Sa oscillator (center wavelength 800 nm), used for electro-optical diagnostics at FLASH, to a locally installed 40.5 MHz erbium-doped fiber laser, operating at 1550 nm. Later, this laser will be replaced by an actively length-stabilized fiber-link distributing the pulses from the 216 MHz master laser oscillator of the machine to lock the diagnostics laser to the optical synchronization system.
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