TUP2WA —  WG-A   (06-Mar-18   16:00—18:00)
Chair: L. Giannessi, Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
Paper Title Page
EEHG Experiment at FERMI  
  • E. Allaria
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  Echo enabled harmonic generation (EEHG) has been recognized as a possible solution to extend the tuning range of externally seeded FELs to wavelength as short as few nm. Previous experiments have confirmed the capabilities to produce bunching at very high harmonic but they have been done only at long wavelength. An experiment to demonstrate EEHG operations at high harmonic and short wavelength is planned at FERMI. With few modifications to the FERMI FEL-2 layout, EEHG will be studied and performances will be compared to other seeding schemes such as high gain harmonic generation (HGHG). Attention will be focused to the spectral purity and to the sensitivity of EEHG and HGHG to microbunching instabilities.  
slides icon Slides TUP2WA01 [19.405 MB]  
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An X-Ray FEL Oscillator for Novel Sciences  
  • K.-J. Kim
    ANL, Argonne, Illinois, USA
  Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, Contract No. DE-AC02-06CH11357
An X-ray FEL Oscillator (XFELO) is capable of producing fully coherent flux of ~1015 photons /s/ (meV bandwidth) over the hard X-ray spectral range 5 to 25 keV. This is higher by about three orders of magnitude than that from the self-amplified-spontaneous-emission (SASE) sources and about six orders magnitudes than the MBA sources. A CW, MHz rep rate, multi-GeV superconducting linac, such as planned at several laboratories is ideally suited for operating an XFELO. The XFELO pulses are also highly stable in contrast to the SASE pulses. In contrast to the ultrafast sciences probed by SASE, the XFELO is well-suited for sciences probing ultra fine spectral resolution. An XFELO can thus greatly extend the parameter space of the techniques established in third generation sources (IXS, XPCS, NRS) as well as opening up entirely new field, for example the nuclear physics of Mössbauer states and fundamental physics with X-ray spectral comb. The performance listed above is based on experimentally demonstrated level of X-ray power density on diamond reflectors and a fixed (4%) out-coupling efficiency. Further enhancement could be feasible if these constraints can be relaxed.
slides icon Slides TUP2WA02 [2.926 MB]  
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TUP2WA03 Harmonic Lasing in X-Ray FELs: Theory and Experiment 68
  • E. Schneidmiller, B. Faatz, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, M. Tischer, M.V. Yurkov
    DESY, Hamburg, Germany
  Harmonic lasing in XFELs is an opportunity to extend operating range of existing and planned X-ray FEL user facilities*. Contrary to nonlinear harmonic generation, harmonic lasing can provide much more intense, stable, and narrow-band FEL beam which is easier to handle due to the suppressed fundamental. Another interesting application of harmonic lasing is Harmonic Lasing Self-Seeded (HLSS) FEL*,** that allows to improve longitudinal coherence and spectral power of a SASE FEL. Recently*** this concept was successfully tested at FLASH2 in the range 4.5 - 15 nm. That was also the first experimental demonstration of harmonic lasing in a high-gain FEL and at a short wavelength (before it worked only in infrared FEL oscillators). In this contribution we describe the concepts of harmonic lasing and of HLSS FEL, and present the experimental results from FLASH2.
* E.Schneidmiller and M.Yurkov, Phys. Rev. ST-AB 15(2012)080702
** E.Schneidmiller and M.Yurkov, Proc. of FEL2013, p.700
*** E.Schneidmiller et al., Phys. Rev. Accel. Beams 20(2017)020705
slides icon Slides TUP2WA03 [3.378 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-TUP2WA03  
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Simulations and Performance Study of an Optimized Longitudinal Phase Space for the Hard X-Ray Self-Seeding at the European XFEL  
  • S. Liu, W. Decking, V. Kocharyan
    DESY, Hamburg, Germany
  • G. Geloni, S. Serkez
    XFEL. EU, Hamburg, Germany
  A two-stage Hard X-ray Self-Seeding (HXRSS) set-up will be implemented at European XFEL in late 2018. For the demonstration of the HXRSS, short electron beam bunches (FWHM ≤ 50 fs) are preferred to mitigate spatio-temperal coupling effect and to fit to the seeding bump width. In preparation for the commissioning of the HXRSS, beam dynamics simulations have been performed to optimize the longitudinal phase space for a 100 pC electron beam with 5 kA peak current. Performance of the optimized longitudinal phase space will be studied using a transverse deflecting structure in early 2018. With the optimized electron beam, HXRSS simulations have been performed for the lower (~3 keV) and the upper (~14 keV) photon energy range planned for the HXRSS operation. The locations of the two HXRSS stages have been studied and chosen to optimize the performance of the upper photon energy with an insignificant effect on the lower one. We will present the longitudinal phase space optimization for the 100 pC case as well as the expected performance of the HXRSS with the optimized set-up.  
slides icon Slides TUP2WA04 [8.959 MB]  
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