THD —  Thursday - Late Afternoon   (29-Aug-19   16:15—18:00)
Chair: R. Geometrante, KYMA, Trieste, Italy
Paper Title Page
THD01
From Femtosecond to Attosecond Coherent Undulator Pulses  
 
  • V.A. Goryashko, P.M. Salén, G.K. Shamuilov
    Uppsala University, Uppsala, Sweden
 
  Funding: Swedish Research Council (VetenskapsrÃ¥det) (grant no. 2016-04593); Stockholm-Uppsala Centre for Free-Electron Laser Research (SUFEL).
In Bohr’s model of the hydrogen atom, the ground-state electron completes one cycle of revolution in 150 attoseconds. Some other processes in atoms and molecules can be even faster. Femtosecond and attosecond pulses of light can provide the resolution needed for studying and ultimately controlling the dynamics of electrons in solids, molecules and atoms. Therefore, there is a strong scientific demand for the development of sources of high-energy, ultrashort, coherent, X-ray pulses. In this talk, we (i) review the characteristic time and length scales in atoms, molecules and nanostructures, (ii) outline the progress on short-pulse generation over time and the state-of-the-art of production of high-energy, ultrashort pulses; (iii) examine the demonstrated and proposed schemes of the generation of femtosecond and sub-femtosecond pulses with FELs, (iv) discuss recent concepts [1] for the production of 100-attosecond pulses.
[1] A. Mak et al., "Attosecond single-cycle undulator light: a review," Reports on Progress in Physics, Vol. 82, 02590 (2019).
 
slides icon Slides THD01 [9.690 MB]  
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THD02
Attosecond Pulses from Enhanced SASE at LCLS  
 
  • A. Marinelli, P.H. Bucksbaum, E. Champenois, J. Cryan, T.D.C. Driver, J.P. Duris, Z. Huang, A.A. Lutman, J.P. MacArthur, Z. Zhang
    SLAC, Menlo Park, California, USA
  • Z. Huang, S. Li, J.P. MacArthur
    Stanford University, Stanford, California, USA
  • M. Kling, P. Rosenberger
    LMU, Garching, Germany
  • A. Zholents
    ANL, Lemont, Illinois, USA
 
  In my talk I will report the generation and diagnostic of GW-scale soft X-ray attosecond pulses with a current-enhanced X-ray free-electron laser. Our method is based on the enhaced SASE scheme, where an electron bunch with high-current spike is generated by the interaction of the relativistic electrons with a high-power infrared pulse. The X-ray pulses generated by the compressed electron beam are diagnosed with angular photoelectron streaking, and have a mean pulse duration of 350 attoseconds. Our source has a peak brightness that is 6 orders of magnitude larger than any other source of isolated attosecond pulses in the soft X-ray spectral region. This unique combination of high intensity, high photon energy and pulse duration enables the investigation of valence electron dynamics with non-linear spectroscopy and single-shot imaging. I will also discuss the generation of two-color attosecond pulses and our future plans for attosecond science at LCLS-II.  
slides icon Slides THD02 [0.260 MB]  
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THD03 FEL Optimization: From Model-Free to Model-Dependent Approaches and ML Prospects 762
 
  • S. Tomin, G. Geloni
    EuXFEL, Schenefeld, Germany
  • M. Scholz
    DESY, Hamburg, Germany
 
  Users beam-time at modern FEL sources is an extremely valuable commodity. Moreover, maximization of FEL up-time must always be performed accounting for stringent requirements on the photon pulse characteristics. These may vary widely depending on the users requests, which poses issues to parallel operation of high-repetition rate facilities like the European XFEL. Therefore, both model-free or model-dependent optimization schemes, where the model might be given, or provided by machine-learning approaches, are of high importance for the overall efficiency of FEL facilities. In this contribution, we review our previous activities and we report on current efforts and progress in FEL optimization schemes at the European XFEL. Finally, we provide an outlook on future developments.  
slides icon Slides THD03 [13.636 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THD03  
About • paper received ※ 21 August 2019       paper accepted ※ 12 September 2019       issue date ※ 05 November 2019  
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THD04
A Novel Optical Undulator Using Array of Pulse-Front Tilted Laser Beams  
 
  • W. Liu
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  Funding: This work is supported by Natural Science Foundation of China (U1632150, 51627901, 61471332, 11675178-11611140102) and Chinese Universities Scientific Fund (WK2310000059).
We report a laser-driven undulator for developing compact ultraviolet-to-X free-electron lasers (FELs), which overcomes the main disadvantages of previous optical and magnetic undulators. It uses an array of transverse-polarized laser beams with alternated phases to provide the periodic deflecting fields. The pulse-front tilt is applied to free the undulating period from the laser wavelength. The transverse electric field of laser is to deflect the electrons in the vacuum, which greatly increases the efficiency and the achievable deflecting forces since it avoids the breakdown of medium. The ultraviolet-to-X FEL with a desirable undulator strength can be achieved by lasers with intensities being orders of magnitude less than that in previous optical undulator, and by electrons with energies being remarkably less than that of magnetic undulator. Thus, it affords a promising way for developing the ultra-compact and powerful FELs.
 
slides icon Slides THD04 [3.388 MB]  
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