| Paper |
Title |
Page |
| TUPB20 |
Large Horizontal Aperture BPM and Precision Bunch Arrival Pickup
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108 |
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- K. E. Hacker, F. Löhl, H. Schlarb
DESY, Hamburg
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The large horizontal aperture chicane BPM and the precision bunch arrival monitor at FLASH will be important tools to stabilize the arrival-time of the beam at the end of the linac. The pickups for these monitors will be paired with front-ends that sample the zero-crossing of the beam transient through the use of electro-optical modulators and sub-picosecond-long laser pulses delivered by the master-laser oscillator. The design of pickups for this front-end requires the consideration of the beam transient shape as well as the amplitude. Simulations and oscilloscope traces from pickups that use or will use the EOM based phase measurement and the expected limitations and benefits of each pickup are presented. In particular, the design for a 5 um resolution BPM with a 10 cm horizontal aperture is demonstrated in terms of its capability to measure the beam energy and its sensitivity to the shape and orientation of the beam.
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| WEPB08 |
Noise and drift characterization of critical components for the laser based synchronization system at FLASH
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250 |
| |
- B. Lorbeer, B. Lorbeer
TUHH, Hamburg
- F. Löhl, F. Ludwig, J. M. Müller, H. Schlarb, A. Winter
DESY, Hamburg
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At FLASH, a new synchronization system based on distributing streams of short laser pulses through optical fibers will be installed and commissioned in 2007. At several end stations, a low drift- and low noise conversion of the optical signal into RF signals is needed. In this paper, we present the influence of photodiodes on the phase stability of the optical pulse streams and investigate the drift performance of the photo-detection scheme for the extraction of the RF signal.
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| WEPB15 |
A Sub-50 Femtosecond bunch arrival time monitor system for FLASH
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262 |
| |
- F. Löhl, K. E. Hacker, H. Schlarb
DESY, Hamburg
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A bunch arrival time monitor system using the future laser based synchronization system at FLASH has been developed. The signal of a beam pick-up with several GHz bandwidth is sampled by a sub-ps laser pulse using a broadband electro-optical modulator. Bunch arrival time deviations are converted into amplitude modulations of the sampling laser pulses which are then detected by a photo-detector. A resolution of 30 fs could be reached, with the capability towards sub-10 fs level. In this paper we describe the design of the optical system and we present recent results.
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| WEPB16 |
First prototype of an optical cross-correlation based fiber-link stabilization for the FLASH synchronization system
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265 |
| |
- F. Löhl, H. Schlarb
DESY, Hamburg
- J. Chen, F. X. Kaertner, J. Kim
MIT, Cambridge, Massachusetts
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A drift free synchronization distribution system with femtosecond accuracy is of great interest for free-electron-lasers such as FLASH or the European XFEL. Stability at that level can be reached by distributing laser pulses from a mode-locked erbium-doped fiber laser master oscillator over actively optical-length stabilized fiber-links. In this paper we present a prototype of a fiber-link stabilization system based on balanced optical cross-correlation. The optical cross-correlation offers drift-free timing jitter detection. With this approach we were able to reduce the timing jitter added by a 400 m long fiber-link installed in a noisy accelerator environment to below 10 fs (rms) over 12 hours.
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| WEPC01 |
Beam Based Measurements of RF Phase and Amplitude Stability at FLASH
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307 |
| |
- H. Schlarb, C. Gerth, W. Koprek, F. Löhl, E. Vogel
DESY, Hamburg
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Beam based techniques to determine the phase and amplitude stability of the photo-cathode laser, the RF gun and superconducting acceleration modules become key tools for the understanding and quality control for FEL operation critical acceleration sub-system. The measurements are used to identify the sources of instabilities, to determine response functions and to optimize RF feedback parameters and algorithm. In this paper, an overview on the measurement techniques and their limitation is given, together with some important results on the currently achieved RF and laser stability.
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| WEPC02 |
Developments at Elettra of the Electronics for the Bunch-Arrival Monitor
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310 |
| |
- L. Pavlovič, T. Korošec, M. Vidmar
Uni LJ, Ljubljana
- M. Ferianis, F. Rossi
ELETTRA, Basovizza, Trieste
- K. E. Hacker, F. Löhl, H. Schlarb
DESY, Hamburg
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Within the framework of the EUROFEL project, a task has been started in 2006 for a joint development of a Bunch Arrival Monitor (BAM), based on the original idea from DESY. ELETTRA is responsible for the development of the VME-controlled clock-delay board of the BAM system. A variable clock-delay circuit (a phase shifter) is required to adjust the acquisition sampling point of the pick-up-modulated optical pulses of the master-laser oscillator. Since the optical pulses have a repetition rate of 40.625MHz (54MHz in the future) and the acquisition sampling frequency is double of this value, the clock-delay module operates in the 80-120MHz frequency range. The clock timing jitter of the acquisition system greatly affects the measurements of the system: the output timing jitter from the clock-delay board should be less than 0.5ps-rms. Therefore, due to the very strict additive timing-jitter requirements, three phase shifter versions were designed, built and phase-noise evaluated. Low-pass-filter implementation achieved 563fs (at 283fs source jitter) of total-system timing jitter, integrated IQ multiplier 365fs (at 188fs of source) and passive IQ modulator 265fs (at 208fs of source).
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| WEPC13 |
Jitter Reduced Pump-Probe Experiments
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337 |
| |
- A. Azima, S. Düsterer, J. Feldhaus, P. Radcliffe, H. Redlin, H. Schlarb
DESY, Hamburg
- M. Meyer
LIXAM, Orsay
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For two-colour pump-probe experiments carried out at the free electron laser FLASH@DESY, the FEL laser pulses in the XUV have to be synchronized with femtosecond precision to optical laser pulses (Ti:Sapphire). An electro-optical sampling diagnostic measures the arrival time jitter of the infrared pump-probe laser pulse in respect to the electron bunch of the FEL. Here, the electron arrival time is encoded spatially into the laser pulse profile and readout by an intensified camera. In this paper we report about the improvement of the temporal resolution of pump-probe experiments on gaseous and solid targets using the arrival time data acquired by the described EO-diagnostic.
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