ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2089-2102 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The design of a diffration grating used as an output coupler for a Fabry–Pérot resonator is presented. We then consider the problem of determining the distortion and the cross-polarization of the incident Gaussian beam. Different types of gratings and planes with straight or curvilinear grooves and elliptical, have been designed and built. The output pattern from a resonator using such a grating has been measured experimentally. We found that the elliptical grating generates the least distortion and cross-polarization. This result is attributed to the geometry of the grooves and is in excellent agreement with numerical calculations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2421-2430 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron beam instabilities occurring in a gyrotron electron beam can induce an energy spread which might significantly deteriorate the gyrotron efficiency. Three types of instabilities are considered to explain the important discrepancy found between the theoretical and experimental efficiency in the case of quasi-optical gyrotrons (QOG): the electron cyclotron maser instability (ECMI), the electrostatic Bernstein instability (BI) and the Langmuir instability (LI). When the magnetic field gradient in drift tubes of QOG is low, the ECMI can develop in the drift tube at very low electron beam currents. Experimental measurements show that with a proper choice of absorbing structures in the beam tunnel, this instability can be suppressed. At high beam currents, the BI can induce a significant energy spread at the entrance of the interaction region. The induced energy spread scales approximately linearly with the electron beam density and for QOG one observes that the beam density is significantly higher than the beam density of an equivalent cylindrical cavity gyrotron. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The parallel velocity distribution function of the weakly relativistic electron beam of a quasi-optical gyrotron has been determined by measuring the Doppler-shifted Electron Cyclotron Emission (ECE) at an angle θ=15° with respect to the external magnetic dc-field. Due to the Doppler shift, the frequency of the spontaneous cyclotron emission at the fundamental (ν0=100 GHz) is upshifted to 140 GHz. A broadening of the spectrum up to 10 GHz [full width at half maximium (FWHM)] was measured. The measured mean frequency agrees well with the theoretical predictions, but the observed line-width, and hence the parallel velocity distribution function, is 2–3 times larger than expected. Considerations on ECE-measurements of the electron beam energy spread, performed at larger angles θ, are also discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3492-3500 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The operation of a 92 GHz quasi-optical gyrotron having a resonator formed by a spherical mirror and a diffraction grating placed in −1 order Littrow mount is presented. A power of 150 kW with a Gaussian output pattern was measured. The Gaussian content in the output was 98% with less than 1% of depolarization. By optimizing the magnetic field at fixed frequency, a maximum efficiency of 15% was reached.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1315-1318 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The operating diagram of a low quality factor, 8 GHz TE°01 gyrotron exhibits oscillations between 6.8 and 7.3 GHz. These oscillations are identified as the backward wave component of the TE°21 traveling mode. As the resonance condition of this mode depends on the average parallel velocity 〈v(parallel)〉 of the beam electrons (ωBW(approximately-equal-to)Ωc/γ−k(parallel)〈v(parallel)〉), the measurement of ωBW for given Ωc and γ is used as a diagnostic for the beam electrons velocity ratio α=〈v⊥〉/〈v(parallel)〉. The values of α, deduced from ωBW through the linear dispersion relation for the electron cyclotron instability in an infinite waveguide, are unrealistic. A nonlinear simulation code gives α values that are in very good agreement with the ones predicted by a particle trajectory code (+10% to +20%). It is found numerically that the particles' velocity dispersion in v⊥ and v(parallel) increases ωBW. This effect explains part of the discrepancy between the values of α inferred from ωBW without velocity dispersion and the expected values.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 519-521 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent experiments on a 100 GHz quasioptical gyrotron have shown that for a large resonator setup [Phys. Fluids B 2, 1654 (1990)] the observed frequency up-shift between the starting current and a current of 10 A corresponds to a shift of 4–5 longitudinal modes. In this Letter it is shown that the interpretation of this frequency up-shift should involve the current-dependent electron beam voltage depression in the beam tunnel and the interaction region for both the single-mode and multimode time evolution codes.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1654-1661 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments on a 100 GHz quasioptical (QO) gyrotron operating at the fundamental (ω=Ωce) are described. Powers larger than 90 kW at an efficiency of about 12% were achieved. Depending on the electron beam parameters, the frequency spectrum of the output can be either single moded or multimoded. One of the main advantages of the QO gyrotron over the conventional gyrotron is its continuous frequency tunability. Various techniques to tune the output frequency have been tested, such as changing the mirror separation, the beam voltage, or the main magnetic field. Within the limitations of the present setup, 5% tunability was achieved. The QO gyrotron designed for operation at the fundamental frequency exhibits simultaneous emission at 100 GHz (fundamental) and 200 GHz (second harmonic). For a beam current of 4 A, 20% of the total rf power is emitted at the second harmonic.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quasi-optical gyrotron (QOG) designed for operation at the fundamental ( fce(approximately-equal-to)100 GHz) exhibits simultaneous emission at fce and 2fce (second harmonic). For a beam current of 4 A, 20% of the total rf power is emitted at the second harmonic. The experimental measurements show that the excitation of the second harmonic is only possible when the fundamental is present. The frequency of the second harmonic is locked by the frequency of the fundamental. Experimental evidence shows that when the second harmonic is not excited, total efficiency is enhanced.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2016-04-08
    Description: With the aim of gaining a better physical insight into linear regimes in gyrotrons, a new linear model was developed. This model is based on a spectral approach for solving the self-consistent system of equations describing the wave-particle interaction in the cavity of a gyrotron oscillator. Taking into account the wall-losses self-consistently and including the main system inhomogeneities in the cavity geometry and in the magnetic field, the model is appropriate to consider real system parameters. The main advantage of the spectral approach, compared with a time-dependent approach, is the possibility to describe all of the stable and unstable modes, respectively, with negative and positive growth rates. This permits to reveal the existence of a new set of eigenmodes, in addition to the usual eigenmodes issued from cold-cavity modes. The proposed model can be used for studying other instabilities such as, for instance, backward waves potentially excited in gyrotron beam tunnels.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2016-06-04
    Description: The geometrical and electronic structures of ScSi 3 −/0 clusters have been studied with the B3LYP, CCSD(T), and CASPT2 methods. The ground state of the anionic cluster was evaluated to be the 1 A 1 of rhombic η 2 -(Si 3 )Sc − isomer, whereas that of the neutral cluster was computed to be the 2 A 1 of the same isomer. All features in the 266 and 193 nm photoelectron spectra of ScSi 3 − cluster were interpreted by the one- and two-electron detachments from the 1 A 1 of rhombic η 2 -(Si 3 )Sc − isomer. The Franck-Condon factor simulation results show that the first broad band starting at 1.78 eV in the spectra comprises several vibrational progression peaks of two totally symmetric modes with the corresponding frequencies of 296 and 354 cm −1 .
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...