Filter Results
5 results
  • In this thesis the design and analysis of SIS-mixers (SIS: superconductor-isolator-superconductor) for the use as low-noise and broad-band detectors in the submm-region for astronomical observations is described. The SIS-mixers have been developed for the frequency band 2 (636-802 GHz) of the Heterodyne Instrument for the Far Infrared (HIFI) on ESA’s space-observatory Herschel. The required performance baseline has been defined by the HIFI-consortium in terms of the estimated noise temperature contribution of the mixer to be 110 K at 636 GHz and 150 K at 802 GHz. In the frequency region between 80 GHz and 900 GHz Heterodyne SIS mixers are established as the best devices for low noise mixing with a high spectral resolution (mixing of the signal radiation with local oscillator, LO). For the HIFI band 2 mixers, the technology of Nb/Al-Al2O3/Nb-junctions has been used with junction areas of 0.5-1.0 um2, a target value for the current density jc of 15 kA/cm2 and a gap-voltage of 2.75-2.77 mV. For the compensation of the SIS-junction’s intrinsic capacitance and the optimized power coupling to the tunnel junction, two types of matching circuits have been theoretically modelled and experimentally studied: (1) three-step transformer single junction devices and (2) double-junction devices. This has been done for two material combinations: for an all-superconductive micro strip NbTiN/SiO2/Nb, and for the superconductor/normal-conductor combination NbTiN/SiO2/Al...,thesis,
    Data Types:
    • Document
  • Astronomische Beobachtungen im Bereich der THz-Frequenzen geben Aufschluss über die Entwicklung der interstellaren Materie in unserem Universum. Als wichtigste Kühllinie dichter Molekülwolken ist die Detektion des Feinstrukturübergangs von einfach-ionisiertem atomarem Kohlenstoff CII bei der Frequenz von 1,9 THz von fundamentaler Bedeutung. Wünschenswert ist das Studium astronomischer Quellen hinsichtlich ihrer Dynamik, Temperatur und Dichte mit möglichst hoher sowohl räumlicher als auch spektraler Auflösung. Heterodynempfänger sind für diese Aufgabe am besten geeignet. Bei dieser Technologie wird das astronomische Signal mittels eines Lokaloszillatoren (LO) auf eine Zwischenfrequenz von wenigen GHz umgesetzt und dann rauscharm weiterverstärkt. Gegenstand der vorliegenden Arbeit ist die Entwicklung und der Aufbau des LOs für den 1,9 THz Frequenzkanal des Mehrkanalheterodynempfängers German REceiver for Astronomy at THz-Frequencies (GREAT) der auf dem Flugzeugobservatorium Stratospheric Observatory For Infrared Astronomy (SOFIA) zum Einsatz kommen wird. Für den Aufbau des LOs wurde auf eine Kombination zweier THz-Strahlungsquellen bestehend aus einem Rückwärtswellenoszillator (Backward-Wave Oscillator, BWO) und einem Frequenzverdreifacher zurückgegriffen. Dieser Ansatz erforderte die Entwicklung einer astigmatisch-abbildenden Submillimeteroptik, um die Leistungsankopplung zwischen BWO und Frequenzverdreifacher zu verbessern...,thesis,
    Data Types:
    • Document
  • The configurational heat capacity, shear modulus and shear viscosity of a series of Na2O–Fe2O3–Al2O3–SiO2 melts have been determined as a function of composition. A change in composition dependence of each of the physical properties is observed as Na2O/(Na2O + Al2O3) is decreased, and the peralkaline melts become peraluminous and a new charge-balanced Al-structure appears in the melts. Of special interest are the frequency dependent (1 mHz–1 Hz) measurements of the shear modulus. These forced oscillation measurements determine the lifetimes of Si–O bonds and Na–O bonds in the melt. The lifetime of the Al–O bonds could not, however, be resolved from the mechanical spectrum. Therefore, it appears that the lifetime of Al–O bonds in these melts is similar to that of Si–O bonds with the Al–O relaxation peak being subsumed by the Si–O relaxation peak. The appearance of a new Al-structure in the peraluminous melts also cannot be resolved from the mechanical spectra, although a change in elastic shear modulus is determined as a function of composition. The structural shear-relaxation time of some of these melts is not that which is predicted by the Maxwell equation, but up to 1.5 orders of magnitude faster. Although the configurational heat capacity, density and shear modulus of the melts show a change in trend as a function of composition at the boundary between peralkaline and peraluminous, the deviation in relaxation time from the Maxwell equation occurs in the peralkaline regime. The measured relaxation times for both the very peralkaline melts and the peraluminous melts are identical with the calculated Maxwell relaxation time. As the Maxwell equation was created to describe the timescale of flow of a mono-structure material, a deviation from the prediction would indicate that the structure of the melt is too complex to be described by this simple flow equation. One possibility is that Al-rich channels form and then disappear with decreasing Si/Al, and that the flow is dominated by the lifetime of Si–O bonds in the Al-poor peralkaline melts, and by the lifetime of Al–O bonds in the relatively Si-poor peralkaline and peraluminous melts with a complex flow mechanism occurring in the mid-compositions. This anomalous deviation from the calculated relaxation time appears to be independent of the change in structure expected to occur at the peralkaline/peraluminous boundary due to the lack of charge-balancing cations for the Al-tetrahedra.
    Data Types:
    • Document
  • Dieser Band enthält 134 Artikel zu Themengebieten der Seismologie, Erdmagnetismus und Gesteinsphysik veröffentlicht durch die Deutsche Geophysikalische Gesellschaft in dem Jahr 1974.,DGG, DFG, SUB Göttingen,Inhaltsverzeichnis: Journal of Geophysics 40 Seegravimetrie (Fleischer, U.) Statistical analysis of the pitch angle distribution of magnetospheric solar protons during geomagnetic activity (Scholer, M., Morfill, G., Hovestadt, D.) Viscosity-depth-structure of different tectonic units and possible consequences for the upper part of converging plates (Meissner, R.) Die Magnetisierung von Bohrkernen aus einem Serpentinit-Vorkommen bei Erbendorf (Oberpfalz) (Schult, A.) Estimates of in situ thermal diffusivity of the Ore-Bearing Rocks in some drillholes in the Skellefte Field (N. Sweden) using the annual temperature wave (Parasnis, D. S.) Geophysical exploration for groundwater in the Lusaka District, Republic of Zambia (Töpfer, K.D., Legg, C. A.) Neuere Versuche zum Dipol-Induktionsverfahren (Leppin, M.) A field evaluation of Caner's broad-band geomagnetic induction instrumentation (Dragert, H.) Seismic noise at 2 Hz in Europe (Plešinger, A.) Crustal structure under the Ionian Sea (Weigel, W.) Heat-Flow Measurements in Swiss Lakes (Von Herzen, R. P.) Makroseismische Abschätzungen von Herdparametern österreichischer Erdbeben aus den Jahren 1905 - 1973 (Franke, A., Gutdeutsch, R.) Long range propagation of seismic energy in the lower lithosphere (Kind, R.) Palaeomagnetism of tertiary volcanic rocks from the Ethiopian southern plateau and the Danakil Block (Schult, A.) Calculation of the shape and position of the last closed field line boundary and the coordinates of the magnetopause neutral points in a theoretical magnetospheric field model (Voigt, G.-H.)) Doppler shift of auroral backscatter signals (Czechowsky, P.) Spherical harmonic analysis of the DS-field during magnetic storms (Schreiber, H.) Note on determining hourly mean values (Larsen, J. C.) Seismic observations in Germany of a 10 t explosion off Scotland (Bonjer, K.-P., Kaminski, W., Kind, R.) A method to reduce the measuring time for spinner magnetometers (Hummervoll, R.) Book Reviews (Mayer, H.) Transverse plasma waves in the solar wind close to the proton gyrofrequency (Rehn, H. W.) Die magnetische Anomalie der Ivreazone (Albert, G.) Second meeting of the European Geophysical Society On a high-frequency method for the measurement of susceptibilities and hysteresis losses of rocks and minerals between nitrogen temperature and 700 °C (Markert, H., Trissl, K.-H., Zimmermann, G. J.) Kinetics of oxidation processes in titanomagnetites (Kropáček, V.) Ultra sound absorption measurements in rock samples at low temperatures (Herminghaus, Ch., Berckhemer, H.) Recordings with the Askania borehole tiltmeter (vertical pendulum) in the frequency range of earth's free oscillations (Flach, D., Große-Brauckmann, W.) Heat flow measurements in northern Italy and heat flow maps of Europe (Haenel, R.) Die Bestimmung der Transmissivität von Grundwasserleitern aus dem Einschwingverhalten des Brunnen-Grundwasserleitersystems (Krauss, I.) Symposium on "Geomagnetic Anomalies, Rock Magnetism and Petrography" (Hahn, A., Hall, D. H., Dunlop, D. J., Kobayashi, Kazuo, Nomura, Masafumi, Lidiak, E. G.) The AEROS mission (Lämmerzahl, P., Bauer, S. J.) The AEROS-EUV Spectrometer (Schmidtke, G., Schweizer, W., Knothe, M.) The retarding potential analyzer on AEROS-B (Spenner, K., Dumbs, A.) Impedance probe. The AEROS-B electron density experiment (Neske, E., Kist, R.) The AEROS neutral and ion mass-spectrometer (Krankowsky, D., Lämmerzahl, P., Bonner, F., Wieder, H.) The neural atmosphere temperature experiment (Spencer, N. W., Pelz, D. T., Niemann, H. B.) Atmospheric drag analysis with the AEROS Satellite (Roemer, Max, Wulf-Mathies, Carsten) Electromagnetic reflections in salt deposits (Thierbach, R.) The structure of the Ries crater from geoelectric depth soundings (Ernstson, K.) Measurements of magnetic total field anomalies in the Hon Graben, Libya (Schult, A.) Correction Book reviews (Theile, B.) Interplanetary magnetic fields and the propagation of cosmic rays (Wibberenz, G.) Intensity and energy spectrum of electrons accelerated in the earth's bow shock (Anderson, K. A.) Evidence from particle precipitation of two-way-convection in auroral latitudes (Hultqvist, B.) Investigation of electron dynamics in the magnetosphere with electron beams injected from sounding rockets (Winckler, J. R.) Cosmic ray electrons in the atmosphere (Fulks, G., Meyer, P.) Cosmic rays underground and the interplanetary magnetic field (Regener, Victor H., Regener, Eric) Harmonic temperature waves in a horizontally layered medium (Mundry, E.) No transform faults on the moon (Stegena, L., Bérczi, Sz.) Dominating trends of the anomalies of the gravity and magnetic fields in NE France and SW Germany (Edel, J. B.) Book Reviews (Strobach, K., Petersen, Nikolai),research,
    Data Types:
    • Document
  • Dieser Band enthält 29 Artikel zu Themengebieten der Geophysik, insbesondere zu Aspekten des Erdmagnetismus und der Seismik, veröffentlicht durch die Deutsche Geophysikalische Gesellschaft in dem Jahr 1982.,DFG, SUB Göttingen,Inhaltsverzeichnis: Journal of Geophysics 51 4039Ar Ages of Rocks and Glasses from the Nördlinger Ries Crater and the Temperature History of Impact Breccias (Staudacher, T., Jessberger, E. K., Dominik, B., Kirsten, T., Schaeffer, O. A.) Tectonic Inferences of Paleomagnetic Data from Some Mesozoic Formations in Central Iran (Wensink, H.) Palaeomagnetic Results from Lower Paleozoic Diabases and Pillow Lavas from the Frankenwald Area (Northwestern Edge of the Bohemian Massif) (Kim, In-Soo, Soffel, H. C.) Palaeomagnetism of Quaternary Volcanics of the East-Eifel, Germany (Böhnel, H., Kohnen, H., Negendank, J., Schmincke, H.-U.) The Effect of Young Oceanic Regions on Frequencies and Damping of free Oscillations of the Earth (Roult, G.) Altitude Characteristics of Radar Aurora as Seen by a 90-MHz Double-Altitude Radar System Operated at Karmaselga, Karelia (Timofeev, E., Miroshnikov, Y.) Observations of Ionospheric and Field-Aligned Currents in the Late Afternoon Sector with Triad and the Scandinavian Magnetometer Array (Sulzbacher, H., Baumjohann, W., Potemra, T. A., Nielsen, E., Gustafsson, G.) Adiabatic Invariant of the Non-Relativistic Particles in the Field of a Shock Wave (Chirkov, A. G., Khodjaev, S. D., Shatalov, S. D., Vasiliyev, V. N.) Comparative Interpretation of Explosion Seismic Data (Ansorge, J., Prodehl, C., Bamford, D.) The Intercept-Time Method – Possibilities and Limitations (Pavlenkova, N. I.) Linearized Solutions of Kinematic Problems of Seismic Body Waves in Inhomogeneous Slightly Anisotropic Media (Červený, V., Jech, J.) Source Parameters of Mine Tremors in the Eastern Part of the Ruhr-District (West-Germany) (Hinzen, K.-G.) Ferromagnetic Resonance g-Factor Measurement on LUNA 20 Soil (Frait, Z., Cimbálníková, A.) Observation of Guided ULF-Waves Correlated with Auroral Particle Precipitation Theoretically Explained by Negative Landau Damping (Klöcker, N.) Ground – Satellite Correlative Study of a Giant Pulsation Event (Hillebrand, O., Münch, J., McPherron, R. L.) Average Diurnal Variations of the Intensity of Geomagnetic Pulsations in the Period Ranges of pc 2–pc 5 Observed at Fürstenfeldbruck During the Years 1960–1971 (Korschunow, A.) Dispersion Effect in Earth Tide Parameters? (Wilhelm, H.) Comments on “Palaeomagnetism of Upper Cretaceous Volcanics and Nubian Sandstones of Wadi Natash, SE Egypt and Implications for the Polar Wander Path for Africa in the Mesozoic” (Schult, A., Hussain, A. G., Soffel, H. C.) Book Reviews (Buntebarth, G., Stegena, L.) Amplitude study of the Pg Phase (Banda, E., Deichmann, N., Braile, L. W., Ansorge, J.) Analysis of Broad-Band Rayleigh Waves: A Possibility for Seismic Discrimination (Hanka, W.) Shear Fracture Development and Seismic Regime in Pyrophyllite Specimens with Soft Inclusions (Sobolev, G., Rummel, F.) The Shape of the Geomagnetic Field Through the Last 8,500 Years Over Part of the Northern Hemisphere (Creer, K. M., Tucholka, P.) The Induced Effects of Geomagnetic Variations in the Equatorial Region (Carlo, L., Singh, B. P., Rastogi, R. G., Agrarwal, A. K.) Parameter Trade-Off in One-Dimensional Magnetotelluric Modelling (Fischer, G., Le Quang, B. V.) A Theory of Forced Magnetohydrodynamic Waves (Krummheuer, F.) Pi2 Magnetic Pulsations, Auroral Break-ups, and the Substorm Current Wedge: A Case Study (Pashin, A. B., Glaßmeier, K. H., Baumjohann, W., Raspopov, O. M., Yahnin, A. G., Opgenoorth, H. J., Pellinen, R. J.) In Memoriam Haakon Brækken 14 April 1902 – 2 Juli 1982 (Saxov, S.) Book Reviews (Jacoby, W. R., Jentzsch, G., Spohn, T., Engelhard, L., Christensen, U.),research,
    Data Types:
    • Document