Author: Stojanovic, N.
Paper Title Page
Coherent Accelerator-based High Field THz Radiation at FLASH II  
  • T. Golz, V. B. Asgekar, B. Faatz, G. Geloni, N. Stojanovic, M. Tischer, P. Vagin, M. Vogt
    DESY, Hamburg, Germany
  • M. Gensch
    HZDR, Dresden, Germany
  • P. Vobly
    BINP SB RAS, Novosibirsk, Russia
  Funding: BMBF grant no. 05K10CHC + 05K10KEB + 05K12CH4
Linear accelerator based light sources with their tunable broad spectral range (THz to hard X-rays regime) and their ability to generate ultra-short pulses with peak intensities many orders of magnitude higher then synchrotron sources, gave rise to a new field of ultrafast physics. In the THz range, the ability of 4th gen. light sources to generate pulses with e-field strengths up to 1 GV/m opened the door to the field of non-linear THz spectroscopy and THz-controlled material science. The main advantage of accelerator-based THz is its scaleability. As the process is not bound to a particular medium, but occurs in the accelerator vacuum, it bypasses the limitation of table top sources. In addition, it has been demonstrated that coherent THz radiation can be generated along femtosecond X-ray pulses in 4th Generation X-ray Light sources such as FLASH [1,2,3] and LCLS [4]. This opens up the opportunity for naturally synchronized THz pump X-ray probe experiments on a few femtosecond time scale [1,2,4]. Here we present the design for the THz source at FLASH2, which takes new findings [5] and challenges into account that we face during the radiation transport to the experimental hall.
MOP060 Demonstration of SASE Suppression Through a Seeded Microbunching Instability 177
  • 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, E. Hass, K. Honkavaara, 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 1355.
Collective effects and instabilities due to longitudinal space charge and coherent synchrotron radiation can degrade the quality of the ultra-relativistic, high-brilliance electron bunches needed for the operation of free-electron lasers. In this contribution, we demonstrate the application of a laser-induced microbunching instability to selectively suppress the SASE process. A significant decrease of photon pulse energies was observed at the free-electron laser FLASH in coincidence with overlap of 800 nm laser pulses and electron bunches within a modulator located approximately 40 meters upstream of the undulators. We discuss the underlying mechanisms based on longitudinal space charge amplification [E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 110701 (2010)] and present measurements.
TUB04 Operation of FLASH with Short SASE-FEL Radiation Pulses 342
  • J. Rönsch-Schulenburg, E. Hass, N.M. Lockmann, T. Plath, M. Rehders, J. Roßbach
    Uni HH, Hamburg, Germany
  • G. Brenner, S. Dziarzhytski, T. Golz, H. Schlarb, B. Schmidt, E. Schneidmiller, S. Schreiber, B. Steffen, N. Stojanovic, S. Wunderlich, M.V. Yurkov
    DESY, Hamburg, Germany
  Funding: The project has been supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301
This paper describes the experimental activity on the generation of very short FEL pulses in the soft x-ray range in the SASE-mode at the high-gain free-electron laser FLASH [1, 2]. The key element, a photo-injector laser which is able to generate laser pulses of about 2 ps FWHM has been optimized and commissioned. It allows the generation of shorter bunches with low bunch charge (of up to 200 pC) directly at the photo-cathode. Initially shorter injector laser pulses and thus shorter bunches eases the required bunch compression factor for short pulses below 10 fs duration which makes operation of the electron beam formation system to be more robust with respect to jitters and collective effects. As a result, overall stability of SASE FEL performance is improved. In the optimal case single-spike operation can be achieved. In this paper the experimental results on production of short electron bunches and the SASE performance using the new injector laser will be shown and the measured electron bunch and FEL radiation properties are discussed. In addition, optimizations of bunch diagnostics for low charge and short bunches are discussed.
slides icon Slides TUB04 [1.201 MB]  
Optical Afterburner for Naturaly Synchronized Pump-probe Experiments at FLASH  
  • N. Stojanovic, A. Al-Shemmary, D. Espeloer, T. Golz, R. Riedel, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  • M. Foerst
    CFEL, Hamburg, Germany
  • M. Gensch
    HZDR, Dresden, Germany
  • F. Tavella
    HIJ, Jena, Germany
  Funding: German Federal Ministry for Education and Research, project 05K10CHC and 05K12CH4
We employ so- called Optical Afterburner [*,**] principle to generate optical replica pulses of X-ray pulse at FLASH (Free Electron LASer in Hamburg). These pulses are naturally synchronized to the FEL pulses and share the same envelope and arrival time, with accuracy down to few femtoseconds. Because of this, Optical Afterburner pulses can be used for complete temporal diagnostics for FEL pulses. Because we shift diagnostics challenge from X-ray to visible range, this significantly simplifies detection. During pulse- duration measurement campaigns at FLASH, Optical Afterburner has been demonstrated as versatile and accurate tool to measure pulse duration of X-ray FEL pulses. In the most recent development we have amplified, Optical Afterburner pulses by three orders of magnitude and will used it in the X-ray/Visible pump-probe experiments for ultimate temporal resolution. We have demonstrated amplification concept at FLASH, where we reach pulse energies above 1uJ at 1MHz repetition rate.
* E.L. Saldin, E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 030701 (2010)
* Proceedings of IPAC2011, San Sebastián, Spain. THPC084
Towards a Novel THz-based Monitor for Subpicosecond Electron Bunches Working at MHz Repetition Rates and Low Bunch Charges  
  • B.W. Green, M. Gensch, S. Kovalev
    HZDR, Dresden, Germany
  • A.S. Fisher
    SLAC, Menlo Park, California, USA
  • T. Golz, N. Stojanovic
    DESY, Hamburg, Germany
  • M. Kuntzsch
    TU Dresden, Dresden, Germany
  The control and measurement of electron bunch properties at the femtosecond (fs) level has become an important field in modern accelerator physics, in particular since these became crucial parameters for the operation of 4th Generation X-ray Light-sources. In order to operate modern-day photon factories such as LCLS and the future European X-FEL reliably, a number of novel approaches have been developed that allow the noninvasive measurement of electron bunch form and arrival time. Some of those are based on the electro-optic detection of the coulomb field of the electron bunches in the electron beamline; some detect the super-radiant THz pulses from the electron bunch. However, none of these concepts allows for pulse-to-pulse detection on a quasi-CW accelerator operating at the MHz repetition rates planned for the next generation of X-ray free electron lasers. In this contribution we present first results from a new monitor concept, based on the single-shot electro-optic detection of super-radiant THz pulses, that has the potential to operate at MHz repetition rates.  
poster icon Poster THP065 [1.966 MB]