Author: Laarmann, T.
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TUA02 Suppression of FEL Lasing by a Seeded Microbunching Instability 289
 
  • C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach
    Uni HH, Hamburg, Germany
  • S. Ackermann, J. Bödewadt, G. Brenner, M. Dohlus, N. Ekanayake, T. Golz, T. Laarmann, T. Limberg, E. Schneidmiller, N. Stojanovic, M.V. Yurkov
    DESY, Hamburg, Germany
  • K.E. Hacker, S. Khan, R. Molo
    DELTA, Dortmund, Germany
 
  Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4, and 05K13PE3 and the German Research Foundation programme graduate school GRK1355.
Collective effects and instabilities due to longitudinal space charge and coherent synchrotron radiation can degrade the quality of the ultra-relativistic, high-brightness electron bunches driving free-electron lasers (FELs). In this contribution, we demonstrate suppression of FEL lasing induced by a laser-triggered microbunching instability at the free-electron laser FLASH. The interaction between the electron bunches and the 800-nm laser pulses takes place in an undulator upstream of the FEL undulators. A significant decrease of XUV photon pulse energies has been observed in coincidence with the laser-electron overlap in the modulator. We discuss the underlying mechanisms based on longitudinal space charge amplification (LSCA) [E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 110701 (2010)] and present measurements.
 
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WEP030 First Lasing of an HGHG Seeded FEL at FLASH 646
 
  • K.E. Hacker, S. Khan, R. Molo
    DELTA, Dortmund, Germany
  • S. Ackermann, Ph. Amstutz, A. Azima, M. Drescher, L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, T. Plath, J. Roßbach
    Uni HH, Hamburg, Germany
  • S. Ackermann, R.W. Aßmann, J. Bödewadt, N. Ekanayake, B. Faatz, I. Hartl, R. Ivanov, T. Laarmann, J.M. Müller
    DESY, Hamburg, Germany
 
  Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K1GU4 and 05K10PE1 and the German Research Foundation program graduate school 1355.
The free-electron laser facility FLASH at DESY operates in SASE mode with MHz bunch trains of high-intensity extreme ultraviolet and soft X-ray FEL pulses. A seeded beamline which is designed to be operated parasitically to the main SASE beamline has been used to test different external FEL seeding methods. First lasing at the 7th harmonic of a 266 nm seed laser using high-gain harmonic generation has been demonstrated. Studies of the influence of the microbunching instability are being pursued.
 
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WEP031 Measurements and Simulations of Seeded Electron Microbunches with Collective Effects 650
 
  • K.E. Hacker, S. Khan, R. Molo
    DELTA, Dortmund, Germany
  • S. Ackermann, J. Bödewadt, M. Dohlus, N. Ekanayake, T. Laarmann, H. Schlarb
    DESY, Hamburg, Germany
  • L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, T. Plath, J. Roßbach
    Uni HH, Hamburg, Germany
 
  Funding: The experiments were carried out at FLASH at DESY. BMBF contract No. 05K10PE1, 05K10PE3, 05K13GU4, and 05K13PE3, and the German Research Foundation program graduate school 1355.
Measurements of the longitudinal phase-space distribution of electron bunches seeded with an external laser were done in order to study the impact of collective effects on seeded microbunches in free-electron lasers. Velocity bunching of a seeded microbunch appears to be a viable alternative to compression with a magnetic chicane under high-gain harmonic generation seeding conditions when the collective effects of Coulomb forces in a drift space and coherent synchrotron radiation in a chicane are considered. Measurements of these effects on seeded electron microbunches were performed with an RF deflecting structure and a dipole magnet which streak out the electron bunch for single-shot images of the longitudinal phase-space distribution. Particle tracking simulations in 3D predicted the compression dynamics of the seeded microbunches with collective effects.
 
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