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| MOPPH068 | Attosecond Pulses from X-Ray FEL with an Energy-Chirped Electron Beam and a Tapered Undulator | 202 |
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| We present a new scheme for generation of attosecond pulses in X-ray SASE FEL. A short slice in the electron beam is strongly modulated in energy by a few-cycle laser pulse in a short undulator, placed in front of the main undulator. Gain degradation within this slice is compensated by an appropriate undulator taper while the rest of the bunch suffers from this taper and does not lase. Three-dimensional simulations with the code FAST predict that short (200 attoseconds) high-power (up to 100 GW) pulses can be produced in Angstrom wavelength range with a high degree of contrast. A possibility to reduce pulse duration to sub-100 attosecond scale is discussed. | ||
| MOPPH069 | Transverse and Longitudinal Coherence Properties of the Radiation from X-Ray SASE FELs | 206 |
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| We present the results of comprehensive numerical studies on transverse and longitudinal coherence of SASE FEL radiation. Development of coherence in exponential gain regime and saturation is studied with the help of similarity techniques. Expected coherence properties of X-ray sourses at the European XFEL, LCLS and SCSS are compared. The simulations were performed with the three-dimensional time-dependent code FAST using a real number of particles in the electron bunch. | ||
| TUBAU05 | Technical Aspects of the Integration of the Optical Replica Synthesizer for the Diagnostics of Ultra-short Bunches into FLASH at DESY | 296 |
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Recently, Saldin et al.* introduced a novel scheme to characterise ultra-short electron bunches in a FEL. The method is based on producing an 'optical copy' of the electron bunch, which can then be easily analysed using well-known non-linear optical techniques. To this end, a near-IR laser beam is overlapped with the electron beam in the first undulator of an optical klystron. In the following dispersive section the laser-induced energy modulation is transformed into a density modulation . The modulated electron bunch then produces a strong optical pulse in the second undulator. Analysis of this near-IR pulse (the optical copy) then provides information about the length, the slice emittance and the slice energy spread of the original electron bunch. We discuss the implementation of such a measurement set-up at the VUV-FEL at DESY and investigate the influence of various parameters on the performance of the device. Topics we address include the electron beam optics of the undulators, quadrupoles and the dispersive chicane, as well as the requirements for the seed laser pulses. The detection and analysis of the near-IR pulse and an extension to the XUV-FEL are also covered.
* E. Saldin, et al. "A simple method for the determination of the structure of ultrashort relativistic electron bunches," Nucl. Inst. and Methods A 539 (2005) 499. |
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| THAAU02 | Fourier Optics Treatment of Classical Relativistic Electrodynamics | 501 |
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| In this paper we present a critical re-examination of Transition Undulator radiation, that has been first investigated a decade ago. We study a realistic undulator setup, which includes an undulator, two straight sections and two bends, before and after the undulator. This allows us to underline an important physical fact: it does not make sense to study the intensity distribution of transition radiation from an undulator without a detailed knowledge of the complete setup. The present paper also helps to point out several misconceptions present in literature regarding Coherent Transition Undulator Radiation. | ||
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