ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • 2020-2024  (1)
  • 1985-1989  (25)
  • 1
    facet.materialart.
    Unbekannt
    Cubesat-class instruments for in situ multi-parameter measurements of the thermosphere (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publikationsdatum: 2023-07-10
    Beschreibung: Described are instruments currently under development for measuring thermospheric winds in situ from a cubesat-class platform. While the primary measurement target is 3D winds, the instruments also return temperature and density measurements, as well as composition information. The instruments are based on mechanical modulation of the rammed flow of the ambient gas. They are similar to larger instruments designed for use on larger platforms, but are accommodated for cubesats with less mass, volume, and power. The principles of measurement and performance models are presented and discussed, and compared to the performance of larger instruments. Prototype designs and plans for laboratory testing are described.
    Sprache: Englisch
    Materialart: info:eu-repo/semantics/conferenceObject
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 2
    Digitale Medien
    Digitale Medien
    Mode conversion and absorption of lower hybrid waves in inhomogeneous magnetic fields (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1968-1978 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: When a cold lower hybrid wave propagates in an inhomogeneous plasma, it undergoes a total mode conversion to the warm wave which is then coupled with the ion Bernstein wave around ion cyclotron harmonic frequencies. Both types of linear mode conversion problems can be described by fourth-order differential equations if the two processes are separated from each other. The combination of the two types of mode conversion when the lower hybrid turning point is in the vicinity of a cyclotron harmonic requires a sixth-order equation with a quadratic coefficient, which is not solvable analytically nor numerically. Another type of sixth-order equation, which has only linear coefficients and represents the three-wave problem marginally, is solved analytically without including the absorption term. Finally, the damping and the absorption of the wave are compared for the unmagnetized dispersion relation, the full magnetized dispersion relation, and the mode conversion analysis as the wave propagates in a magnetically confined plasma with slab geometry.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.866644
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    An algorithm to solve the linear mode conversion problem in a weakly inhomogeneous plasma (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 145-154 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In a previous article, the wave equation for electromagnetic and electrostatic waves propagating in a weakly inhomogeneous plasma was studied assuming an ordinary differential equation of the Laplace type. An algorithm was developed, based on the contour integral formalism, that gives a prescription for calculating the connection formulas between the set of fast and slow propagating waves. Physical problems connected to the evanescent solutions were not treated, however, so the complete set of solutions was not obtained. In this paper, the method is extended to include both propagating and nonpropagating waves so that a complete set of solutions is obtained, permitting the construction of the Green function and the inclusion of localized sources or sinks.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.865175
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    Wave heating at the third harmonic of the ion-cyclotron frequency (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 1800-1809 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: For heating of fusion reactors, heating at the third harmonic of deuterium is shown to be an attractive possibility since absorption is still strong and the plasma core is accessible. The higher frequency also makes the application of waveguide launchers more attractive because of the smaller size. The calculation model is a deuterium–tritium plasma with a small α component. The dispersion relation leads to a sixth-order mode conversion equation solved by the Green function formalism which converts it to an integral equation. Numerical studies for the effects of absorption find the analytic transmission coefficient to be exact, and empirical formulas are given for the reflection and conversion coefficients and the power balance between the deuterium and helium. Conservation of energy is also discussed in some detail.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.864923
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 5
    Digitale Medien
    Digitale Medien
    Radio frequency heating in the ion-cyclotron range of frequencies (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2645-2677 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Both the theory of the absorption process in the ion-cyclotron range of frequencies and some of the experiments which slow the promise and problems with radio frequency plasma heating in this range are discussed. It is shown that mode conversion is invariably involved in the process and so an extensive review of mode conversion theory, expecially as it applies to problems with back-to-back cutoff-resonance pairs, is included. This includes a discussion of the tunneling equation with and without absorption effects and with and without energy conservation. The general theory is applied to various ion-cyclotron harmonics, the two-ion hybrid resonance, and to a case where a wave converts to a Bernstein mode at the plasma edge. The results are given analytically for a variety of cases without absorption, and empirical formulas are given for the second and third harmonics of the ion-cyclotron frequency, which include effects of absorption. Various problem areas in the theory are also discussed with some of the limitations caused by the approximations involved. A number of experiments are also discussed which show effective heating, and some show the features of the mode conversion process, indicating that the general processes of absorption are reasonably well understood. Areas where further work is necessary, both in fundamental theory and in comparing theory with experiment, are also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.865224
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 6
    Digitale Medien
    Digitale Medien
    Parabolic approximation method for the mode conversion-tunneling equation (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 340-349 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The derivation of the wave equation that governs ion cyclotron range of frequencies (ICRF) wave propagation, absorption, and mode conversion within the kinetic layer in tokamaks has been extended to include diffraction and focusing effects associated with the finite transverse dimensions of the incident wave fronts. The kinetic layer considered consists of a uniform density, uniform temperature slab model in which the equilibrium magnetic field is oriented in the zˆ direction and varies linearly in the xˆ direction. An equivalent dielectric tensor, as well as a two-dimensional energy conservation equation, are derived from the linearized Vlasov–Maxwell system of equations. A generalized, but approximate form of the mode conversion-tunneling equation is then extracted from the Maxwell equations, using the parabolic approximation method in which transverse variations of the wave fields are assumed to be weak in comparison to the variations in the primary direction of propagation. Numerical solutions of this approximate wave equation agree well with solutions to the exact wave equation within the kinetic layer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859208
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 7
    Digitale Medien
    Digitale Medien
    Dispersion relations for the lower hybrid frequency range (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1123-1129 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The hot plasma electrostatic dispersion relation for the lower hybrid frequency range has been cast into a form without any sums using the method of steepest descents. This new form of the dispersion relation with the exact resonance term, which is valid for general complex wavenumber and each term of which is identified according to its role of representing physical waves, is shown to be accurate and to be reducible to an expression obtained by Brambilla [Plasma Phys. 18, 699 (1976)] when some approximations are taken. A very simple dispersion relation is also obtained without singular terms near the high ion cyclotron harmonics that are encountered by lower hybrid waves propagating in inhomogeneous magnetic fields. Finally, the damping rate in space is numerically calculated using the equation derived and compared with the result from the unmagnetized ion dispersion relation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.866740
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 8
    Digitale Medien
    Digitale Medien
    Magnetic surface mapping with highly transparent screens on the Auburn torsatron (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 460-466 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In stellarator-type magnetic confinement devices (of which the torsatron is one), the magnetic field is produced entirely by external, current-carrying coils. Two methods for mapping magnetic surfaces in the Auburn torsatron were tested and compared, both of which involve the use of highly transparent screens. The first method consists of coating the screen with a phosphor that emits light when struck by electrons emitted by an electron gun. A pattern representative of a magnetic surface is formed on the screen, and this pattern is recorded photographically. The second method uses an uncoated screen to collect electrons emitted from an emissive probe, which is scanned over a poloidal cross section of the torus. Under certain conditions, the collected current is a constant over a particular magnetic surface so that a contour plot of the current versus position is equivalent to a plot of the magnetic surfaces. Parametric studies of the two methods are presented, and the effectiveness of each technique is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1139861
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 9
    Digitale Medien
    Digitale Medien
    Magnetic surface mapping with an emissive filament technique on the Auburn torsatron (1987)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 509-515 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Torsatron and stellarator plasma confinement devices rely on magnetic surface mapping to determine the critical vacuum magnetic field structure. A recently developed method employing an emissive filament offers some advantages over the traditional technique of mapping with a directed electron beam. On the Auburn torsatron a comparative study between the emissive filament and directed electron beam techniques has been conducted. The parameters varied in the comparative study are filament geometry, emission current, bias voltage, background gas pressure, and magnetic field strength. This comparative study indicates that the emissive filament technique is reliable over a broad and easily accessible range of parameters. We have also measured the spatial distribution of electrons on a given magnetic surface. As an application of the emissive filament technique, the optimization of the magnetic surfaces on the Auburn torsatron is shown.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1139261
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 10
    Digitale Medien
    Digitale Medien
    A new radiative single-crystal diffractometer microfurnace incorporating MgO as a high-temperature cement and internal temperature calibrant (1986)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 19 (1986), S. 1-6 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: A new radiative microfurnace has been developed for high-temperature single-crystal work on the four-circle diffractometer. The microfurnace is fairly easy to construct and can be operated at temperatures up to 1270 K with a precision of ± 6 K. A calibrated shunt in the circuitry of the microfurnace is used to determine the microfurnace's resistance, current draw and power usage for any given temperature during a diffraction experiment. A procedure for mounting single crystals in a refractory cement that can be used as an internal calibrant of temperature is also described. The thermal expansion properties of periclase (MgO) have been reinvestigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S002188988609009X
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...