Author: Bluem, H.
Paper Title Page
WEA04 First Lasing from a High Power Cylindrical Grating Smith-Purcell Device 611
  • H. Bluem, R.H. Jackson, J.D. Jarvis, A.M.M. Todd
    AES, Medford, New York, USA
  • J.T. Donohue
    CENBG, Gradignan, France
  • J. Gardelle, P. Modin
    CEA, LE BARP cedex, France
  Funding: Work supported by ONR under Contract No. N00014-10-C-0191 and N62909-13-1-N62.
Many applications of THz radiation remain impractical or impossible due to an absence of compact sources with sufficient power. A source where the interaction occurs between an annular electron beam and a cylindrical grating is capable of generating high THz power in a very compact package. The strong beam bunching generates significant power at the fundamental frequency and harmonics. A collaboration between Advanced Energy Systems and CEA/CESTA has been ongoing in performing proof-of-principle tests on cylindrical grating configurations producing millimeter wave radiation. First lasing was achieved in such a device. Further experiments performed with a 6 mm period grating produced fundamental power at 15 GHz, second harmonic power at 30 GHz and although not measured, simulations show meaningful third harmonic power at 45 GHz. Comparison with simulations shows very good agreement and high conversion efficiency. Planned experiments will increase the frequency of operation to 100 GHz and beyond. Ongoing simulations indicate excellent performance for a device operating at a fundamental frequency of 220 GHz with realistic beam parameters at 10 kV and simple extraction of the mode.
slides icon Slides WEA04 [2.344 MB]  
WEB04 The New IR FEL Facility at the Fritz-Haber-Institut in Berlin 629
  • W. Schöllkopf, W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, A. Paarmann, G. von Helden
    FHI, Berlin, Germany
  • H. Bluem, D. Dowell, R. Lange, J. Rathke, A.M.M. Todd, L.M. Young
    AES, Medford, New York, USA
  • S.C. Gottschalk
    STI, Washington, USA
  • U. Lehnert, P. Michel, W. Seidel, R. Wünsch
    HZDR, Dresden, Germany
  A mid-infrared oscillator FEL has been commissioned at the Fritz-Haber-Institut. The accelerator consists of a thermionic gridded gun, a subharmonic buncher and two S-band standing-wave copper structures [1,2]. It provides a final electron energy adjustable from 15 to 50 MeV, low longitudinal (<50 keV-ps) and transverse emittance (<20 π mm-mrad), at more than 200 pC bunch charge with a micro-pulse repetition rate of 1 GHz and a macro-pulse length of up to 15 μs. Regular user operation started in Nov. 2013 with 6 user stations. Pulsed radiation with up to 100 mJ macro-pulse energy at about 0.5% FWHM bandwidth is routinely produced in the wavelength range from 4 to 48 μm. We will describe the FEL design and its performance as determined by IR power, bandwidth, and micro-pulse length measurements. Further, an overview of the new FHI FEL facility and first user results will be given. The latter include, for instance, spectroscopy of bio-molecules (peptides and small proteins) conformer selected or embedded in superfluid helium nano-droplets at 0.4 K, as well as vibrational spectroscopy of mass-selected metal-oxide clusters and protonated water clusters in the gas phase.
[1] W. Schöllkopf et al., MOOB01, Proc. FEL 2012.
[2] W. Schöllkopf et al., WEPSO62, Proc. FEL 2013.
slides icon Slides WEB04 [12.785 MB]