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polarization

Paper Title Other Keywords Page
TUPB26 Characterisation of the Systematic Effects of the Insertion Devices with Photon Beam Position Monitors photon, undulator, insertion, insertion-device 126
 
  • E. D. van Garderen, M. Böge, J. T.M. Chrin, J. Krempasky, V. Schlott, T. Schmidt, A. Streun
    PSI, Villigen
  The X-ray photon monitors at Swiss Light Source are used for beam-position stabilisation down to sub-micron level. The beam position changes are mainly induced by changing the insertion device (ID) settings. An ID correction scheme involves both digital beam-position monitors (DBPM) located inside the storage ring and analog photon monitors (XBPM) located inside beamline front-ends. However, a beam-position correction scheme optimised for the electron beam is not automatically optimal for the photon beam. A sub-micron stability of the photon beam by changing the ID-settings is possible only if the XBPM readouts are well characterised for each considered ID-setting. We account for some limitations of the XBPM readouts as well as for examples where a sub-micron stability for all considered ID-settings is achieved.  
 
WEPB03 Femtosecond Yb-Doped Fiber Laser System at 1 um of Wavelength with 100-nm Bandwidth and Variable Pulse Structure for Accelerator Diagnostics laser, electron, radiation, diagnostics 235
 
  • A. Winter, B. Steffen
    DESY, Hamburg
  • F. O. Ilday
    Bilkent University, Bilkent, Ankara
  Laser-based diagnostic systems play an increasingly important role in accelerator diagnostics in, for instance, measurements of the electron bunch length. To date, the laser system of choice for electro-optic experiments has been the Ti:Sa laser. These offer nJ pulse energies at fixed repetition rate between 50-100 MHz, which is not well suited to the bunch structure of facilities such as FLASH (several hundred pulses with 1 MHz spacing at 1-5 Hz repetition rate).The limited robustness, stability and operability of Ti:Sa systems make them less than an ideal candidate for a continuously running measurement system requiring minimal maintenance. Fiber lasers represent a promising alternative, since gating and subsequent amplification is simple and of low cost, hence a pulse pattern corresponding exactly to the linac bunch pattern can be generated. Furthermore, these lasers offer superior robustness at a fraction of the cost of a Ti:Sa laser and have been shown to work without maintenance for several months and longer. Here, we present an ytterbium-doped fiber laser system with 80 nm bandwidth and multi-nJ pulse energy with adjustable bunch pattern for use in electro-optic experiments.  
 
WEPB15 A Sub-50 Femtosecond bunch arrival time monitor system for FLASH laser, pick-up, electron, feedback 262
 
  • F. Löhl, K. E. Hacker, H. Schlarb
    DESY, Hamburg
  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.  
 
WEPB16 First prototype of an optical cross-correlation based fiber-link stabilization for the FLASH synchronization system laser, feedback, free-electron-laser, electron 265
 
  • F. Löhl, H. Schlarb
    DESY, Hamburg
  • J. Chen, F. X. Kaertner, J. Kim
    MIT, Cambridge, Massachusetts
  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.  
 
WEPC22 Synchronization of a 3GHz Repetition Rate Harmonically Mode-Locked Fiber Laser for Optical Timing Applications laser, feedback, controls, linac 358
 
  • L. Banchi, M. Ferianis, F. Rossi
    ELETTRA, Basovizza, Trieste
  • A. Bogoni, P. Ghelfi, L. Poti'
    CNIT, Pisa
  We have successfully stabilized a 3GHz Harmonically Mode-Locked fiber ring laser by a PLL feedback control of the cavity length to reduce the pulses RMS timing jitter. The laser cavity is composed of all PM fibers and components to eliminate polarization instabilities and to reduce the vibration sensitivity. The laser stability in terms of timing jitter was around 9ps in the range 10Hz-10MHz. Using a PLL scheme we synchronized the laser repetition rate to an ultra stable RF generator. The noise characteristics of the laser output were measured by observing the SSB noise spectra of the 1st harmonic, from 10Hz to the Nyquist frequency (1.5GHz). We have obtained a global reduction of fiber laser timing jitter value down to less than 100fs in the range 10Hz-10MHz; a complete overlapping between the laser and the RF generator spectral profiles in the loop bandwidth has been observed. An extended investigation has been performed to estimate the phase noise spectra and timing jitter up to 1.5GHz. By doing so, the contribution of the laser supermodes to the phase noise has been taken into account as well, to quantify the true value of the total RMS timing jitter of the optical pulses.