Inaug.-diss.--Erlangen. / Lebenslauf.

Inaug.-diss.--Kiel. / Lebenslauf.

No description available.

No description available.

The work reported here is a proton magnetic resonance investigation of some polyatomic gases. Pulsed nuclear magnetic resonance techniques were used throughout. Little systematic work on gases using this technique has been reported hitherto, and the present study clearly indicates the potentialities of nuclear magnetic resonance experiments for the investigation of certain physical processes occurring in gases. The gases studied were hydrogen (H₂), methane (CH₄), ethane (C₂H₆) and ethylene (C₂H₄). A spectrometer and ancilliary equipment have been constructed enabling measurements to be made at 30 Mc/s, over a temperature range from 35K° to 300K° using gas pressures up to 200 atmospheres. In hydrogen, the spin-lattice relaxation time, T₁, was studied as a function of the density, temperature and ortho-para concentration of the gas. In the "dilute" gas region, T₁ was found to increase linearly with density at fixed temperature, indicating that the relaxation process is of intra-molecular origin and that studies of T₁ are able to yield valuable information on the asymmetric part of the intermolecular interaction. The temperature dependence of T₁ (at fixed density) was studied in the "dilute" gas between 35K° and 300K°, and quantum effects were discovered at low temperatures. In the dense gas, at low temperatures, T₁ was found to be a very rapidly increasing function of density at fixed temperature. In the dilute gas, T₁, at fixed density and temperature, was found to increase with increasing ortho-hydrogen concentration, indicating that the cross-section for a reorientation collision of two orthohydrogen molecules is greater than that for a collision between an ortho-molecule and a paramolecule. Diffusion measurements in hydrogen were carried out, at 78K°, as a function of density in the "dilute" gas, and it has been shown that the coefficient of self-diffusion is inversely proportional to density. The spin-spin relaxation time, T₂, for hydrogen at 78K° has been found to vary linearly with density, in the "dilute" gas, and T₂ = 0.8 T₁. In all the hydrocarbon gases studied, the relaxation process was governed by a single exponential function of time, thus enabling a unique relaxation time T₁ to be defined. In the "dilute" gas, T₁ was found to vary linearly with density. An estimate has been made of the mean square angle of rotation of a methane molecule and of an ethylene molecule per collision, with a view to examining the applicability of a rotational diffusion model for molecular reorientation in these gases. In methane, T₁ has been studied as a function of density just above the critical point for this gas and at room temperature. The effect of traces of oxygen on the relaxation process ("impurity relaxation") in the "dilute" and "dense" gas regions has been studied also. T₁ has been studied in ethane above and below the critical point, and in ethylene above the critical point, in the "dilute" and "dense" gas regions. The oxygen impurity effects have been found to be very marked indeed in the case of ethylene. In the course of this work, a n.m.r. method has also been evolved for the measurement of the compressibility of a gas. A programme of future n.m.r. work on gases, suggested by the results obtained and experience gained in this work, is outlined. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis describes the design of a magnetometer for recording geomagnetic micropulsations. The nuclear magnetic resonance phenomenon of hydrogen nuclei in water is utilized in the sensing unit of a feedback system, the feedback current being recorded as a measure of the geomagnetic variation. The thesis establishes the feasibility of a feedback system magnetometer. The system transfer function is derived and from it the sensitivity, stability, steady state error and dynamic range are determined. The dispersion mode signal of nuclear magnetic resonance obtained experimentally is shown and compared with that predicted theoretically. The advantages of a feedback system are indicated. The difficulty in closing the feedback loop is discussed and methods for overcoming this problem are suggested. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Direct current controlled transductors, now known as magnetic amplifiers, were used successfully by the Germans in the 1939-1945 war for the amplification and mixing of powers down to a microwatt. The desire to know more about their operations than has been given in various periodicals prompted this thesis. An explanation of magnetic amplifier action is given and the waveforms of flux and output current predicted. The behaviour of circuits containing a magnetic amplifier is then explained by the use of waveforms and a mathematical investigation is made. A use for a magnetic amplifier in an oscillator tank circuit is described. Graphs of the characteristics of the magnetic amplifier and photographs of the waveforms are shown and the observed waveforms compared with the predicted ones. A sensitivity test on three circuits containing a magnetic amplifier is described and results given showing that by placing a condenser across the supply windings increases the sensitivity considerably but decreases the power amplification. The proper way to secure a thorough understanding of the properties of the magnetic amplifier by the use of an oscilloscope is discussed and the thesis concludes by listing the advantages and disadvantages of a magnetic amplifier. The mathematical approach to the solution of the magnetic amplifier problem using Frolich's equation for the magnetization curve is given in a special appendix. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The magneto-sphere may be considered as consisting of two regions the tail and region of closed lines of force. The interchange of field lines between these two region is important in magnetospheric processes. Transport of magnetic field lines from the closed region into the tail may occur by Dungey's mechanism or by viscous interaction of the magnetosphere with the solar wind. Transport from the tail to the closed region occurs by recombination through the neutral sheet. Convective flow within the closed region is controlled by the “foot dragging” effect which arises from the discharging action of the ionosphere on flux tubes. The model of polar substorms presented is a flow or time sequence as follows: (1) Field lines are dragged from the closed region into the tail by the solar wind with a resulting storage of potential energy in the tail. (2) The polar substorm begins when the field lines recombine in an implosive fashion at the neutral sheet, releasing the stored potential energy. (3) The recombined flux tubes are added to the nightside of the closed region as a giant bulge. (4) The bulge drives are turn flow of flux tubes towards the dayside in the closed region. It is likely that recombination is initiated by the formation of a neutral point at about 13 or 14 earth radii in the antisolar direction and occurs across a width of tail of about 6 or 7 earth radii and that 10⁸ webers are annihilated in a time of about 1/2 hour. The recombination iis probably stopped by the build-up of a giant bulge on the nightside and the closed region which maps to the earth’s surface along fieldlines as the auroral break-up bulge and which, as i t spreads out over the nightside of the region of closed fieldlines causes the observed auroral effects. The Pedersen current is not expected to produce significant magnetic effects at the surface of the earth except at anomalies in ionospheric conductivity. Such an anomaly along the auroral arcs can explain the westward electrojet. However, it seems probable that the remainder of the polar cap current system is the result of Hall currents. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

This thesis explores the basic theory, design and construction of electron spin resonance spectrometer.

No description available.