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  • 2000-2004  (1)
  • 1990-1994  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Experimental considerations concerning the velocity measurement of the relativistic electron beam in a gyrotron by means of Thomson scattering (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2229-2236 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The feasibility of Thomson scattering to determine the beam velocity in a gyrotron has been analyzed and preliminary experiments to implement such a system on our 100 GHz quasi-optical gyrotron are reported. Although the project had to be abandoned due to technical problems, the conclusions are that for the 90° scattering arrangement discussed it should be possible to determine at least one velocity component with an acceptable signal-to-noise ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354704
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ion temperature measurements in a tokamak by collective Thomson scattering (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1993-1998 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Collective Thomson scattering, using a high-power pulsed D2O laser at 385 μm and a heterodyne receiver system, has provided local ion temperature (Ti) measurements of the plasma in the tokamak chauffage Alfvén (TCA) tokamak. Recent improvements in the noise-equivalent power of the Schottky barrier diode mixers permitted us to achieve a typical precision of ±12% for a single shot measurement at densities above 1020 m−3. Even at densities of standard TCA discharges (5×1019 m−3) the uncertainty is better than ±25%. For the interpretation of the measured spectra and the evaluation of Ti the local value of the electron temperature (Te) is an important parameter. Therefore, Te was measured simultaneously by incoherent Thomson scattering at 0.694 μm during a series of shots. The density was obtained from a far-infrared interferometer. An independent measurement of Ti on TCA can be obtained from a neutral particle analyzer. Comparison of the results from the two methods showed good agreement. The precision of a Ti measurement depends strongly on the plasma density. Since an uncertainty of ±25% at standard densities may still not be regarded as satisfactory, further investigations using a numerical simulation code have been carried out to find ways of improvement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348772
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Single-mode operation of a hybrid optically pumped D2O pulsed far-infrared laser (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1445-1449 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have achieved single-mode operation in a pulsed hybrid optically pumped D2O far-infrared laser. The active volume of the resonator was divided into two sections separated by a thin plastic foil. The larger section served as the main gain medium and the shorter section as the mode selective element. The vapor pressure in the smaller volume was either very low or alternatively about three times higher than the pressure in the main part. In both cases single-mode operation was achieved without any reduction of the total output energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346671
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced Third-Order Nonlinearity in Semiconductors Giving Rise to 1 THz Radiation (2000)
    Springer
    International journal of infrared and millimeter waves 21 (2000), S. 593-602 
    Details
    ISSN: 1572-9559
    Keywords: frequency conversion ; infrared optical materials ; semiconductors ; high power MM waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Third harmonic generation (THG) efficiency is shown to be a greatly enhanced at the onset of inelastic scattering of electrons on optic phonons. Scaling experiments are performed on n-type InP at the pump wave frequency of 9.43 GHz at 80 K. Monte Carlo modeling is employed for scaling the effect to the 3rd harmonic frequency of 1 THz. The THG efficiency in n-type GaAs and InP as well as in the wurtzite phase of n-type InN and GaN compound crystals is compared to that in n-type Si. The efficiency maximum is found to weaken due to the quasi-elastic scattering on acoustic phonons and elastic scattering on ionized impurities. Nevertheless, the THG efficiency at 1 THz in InP crystals cooled down to liquid nitrogen temperatures is predicted to be 2 orders of magnitude higher than the reference value of 0.1% experimentally recorded up to now in n-type Si.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006635920911
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    Paper (German National Licenses)
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