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| MOBAU04 |
Optical Klystron Enhancement to SASE X-Ray FELs
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29 |
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- Y. T. Ding, P. Emma, Z. Huang
SLAC, Menlo Park, California
- V. Kumar
RRCAT, Indore (M. P.)
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The optical klystron enhancement to self-amplified spontaneous emission (SASE) free electron lasers (FELs) is studied in theory and in simulations. In contrast to a seeded FEL, the optical klystron gain in a SASE FEL is not sensitive to any phase mismatch between the radiation and the microbunched electron beam. The FEL performance with the addition of four optical klystrons located at the undulator long breaks in the Linac Coherent Light Source (LCLS) shows significant improvement if the uncorrelated energy spread at the undulator entrance can be controlled to a very small level. In addition, FEL saturation at shorter x-ray wavelengths (around 1.0 angstrom) within the LCLS undulator length becomes possible. We also discuss the application of the optical klystron in a compact x-ray FEL design that employs relatively low electron beam energy together with a shorter-period undulator.
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| MOPPH042 |
An Analysis of Shot Noise Propagation and Amplification in Harmonic Cascade FELs
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130 |
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- Z. Huang
SLAC, Menlo Park, California
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The harmonic generation process in a harmonic cascade (HC) FEL is subject to noise degradation which is proportional to the square of the total harmonic order*. In this paper, we study the shot noise evolution in the first-stage modulator and radiator of a HC FEL that produces the dominant noise contributions. We derive the effective input noise for a modulator operating in the low-gain regime, and analyze the radiator noise for a density-modulated beam. The significance of these noise sources in different harmonic cascade designs is also discussed.
* E. Saldin, E. Schneidmiller, M. Yurkov, Opt. Commun. 202, 169 (2002).
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| MOPPH054 |
FERMI @ Elettra: A Seeded FEL Facility for EUV and Soft X-Rays
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166 |
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- J. N. Corlett, L. R. Doolittle, W. M. Fawley, S. M. Lidia, G. Penn, I. V. Pogorelov, J. Qiang, A. Ratti, J. W. Staples, R. B. Wilcox, A. Zholents
LBNL, Berkeley, California
- E. Allaria, C. J. Bocchetta, D. Bulfone, F. C. Cargnello, D. Cocco, P. Craievich, G. D'Auria, M. B. Danailov, G. De Ninno, S. Di Mitri, B. Diviacco, M. Ferianis, A. Galimberti, A. Gambitta, M. Giannini, F. Iazzourene, E. Karantzoulis, M. Lonza, F. M. Mazzolini, G. Penco, L. Rumiz, S. Spampinati, G. Tromba, M. Trovo, A. Vascotto, M. Veronese, M. Zangrando
ELETTRA, Basovizza, Trieste
- M. Cornacchia, P. Emma, Z. Huang, J. Wu
SLAC, Menlo Park, California
- W. Graves, F. X. Kaertner, D. Wang
MIT, Middleton, Massachusetts
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We describe the conceptual design and major performance parameters for the FERMI FEL project funded for construction at the Sincrotrone Trieste, Italy. This user facility complements the existing storage ring light source at Sincrotrone Trieste, and will be the first facility to be based on seeded harmonic cascade FELs. Seeded FELs provide high peak-power pulses, with controlled temporal duration of the coherent output allowing tailored x-ray output for time-domain explorations with short pulses of 100 fs or less, and high resolution with output bandwidths of the order of meV. The facility uses the existing 1.2 GeV S-band linac, driven by electron beam from a new high-brightness rf photocathode gun, and will provide tunable output over a range from ~100 nm to ~10 nm, and APPLE undulator radiators allow control of x-ray polarization. Initially, two FEL cascades are planned, a single-stage harmonic generation to operate over ~100 nm to ~40 nm, and a two-stage cascade operating from ~40 nm to ~10 nm or shorter wavelengh, each with spatially and temporally coherent output, and peak power in the GW range.
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| THBAU05 |
Precision Measurement of the Undulator K Parameter using Spontaneous Radiation
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548 |
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- J. J. Welch, J. Arthur, P. Emma, J. B. Hastings, Z. Huang, H.-D. Nuhn, P. Stefan
SLAC, Menlo Park, California
- R. M. Bionta
LLNL, Livermore, California
- R. J. Dejus, B. X. Yang
ANL, Argonne, Illinois
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Obtaining a precise and uniform value of the undulator parameter, K, over the full undulator length is critical for producing high-gain FEL radiation, especially in a hard x-ray source such as the LCLS. At an FEL wavelength of 1.5-Å the relative variation of K over the full undulator must be (dK/K)rms < 0.015%. Transverse misalignments, construction errors, radiation damage, and temperature variations all contribute to a different K value in each few-meter-long undulator segment. It is therefore important to measure relative K precisely, after installation and alignment, using beam-based techniques, if possible. We propose a fairly simple method using the angle-integrated spontaneous radiation spectrum of two interfering undulators, and the natural shot-to-shot energy centroid jitter of the electron beam, to measure the relative K error between two segments using both ideal and measured undulator fields. By 'leap-frogging' to different pairs of undulators with extended separations we hope to confirm or correct the value of K, including proper tapering, over the entire 130-m long FEL undulator.
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| THPPH062 |
Calculation of the Beam Field in the LCLS Bunch Length Monitor
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728 |
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- G. V. Stupakov, Y. T. Ding, Z. Huang
SLAC, Menlo Park, California
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Maintaining a stable bunch length and peak current is a critical step for the reliable operation of a SASE based x-ray source. In the LCLS, a bunch length monitor (BLM) right after the bunch compressors is proposed based on the coherent radiation generated by the short electron bunch*. Due to its diagnostic setup, the standard far field synchrotron radiation formula and well-developed numerical codes do not apply for the analysis of the BLM performance. In this paper, we develope a calculation procedure to take into account the near field effect, the effect of a short bending magnet, and the diffraction effect of the radiation transport optics. We find the frequency response of the BLM after the first LCLS bunch compressor and discuss its expected performance.
* J. Wu, P. Emma, Z. Huang, Proceedings of 2005 Particle Accelerator Conference 428.
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