A survey of 21-cm line emission at points equally spaced over the entire sky visible from Penticton, British Columbia, has been made, and the profiles obtained at the intermediate galactic latitudes have been used to determine several of the properties of the distribution of the gas in the solar neighbourhood and to study the dynamics of the gas including the determination of solar motion with respect to gas, the distribution of random velocities and the departure of gas velocities from circular motion. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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Thesis--Utrecht. / Summary in Dutch. Includes bibliographical references.

Thesis--California Institute of Technology, 1970.

The problem of interpreting the small systematic displacements of solar absorption lines towards longer wavelengths relative to the corresponding laboratory wave-lengths – the so-called solar red shifts – has ranked as one of the most controversial problems in solar physics ever since its discovery by Jewell in 1896. The observational and theoretical difficulties which confronted the pioneer workers in this field are reviewed in Chapter I of this thesis. The year 1920 marks the beginning of a new phase in the development of the problem, since this was when Saha introduced his Ionization Theory which formed a completely new conception of the physical conditions prevailing in the solar atmosphere. At the same time, the announcement that an eclipse experiment made in 1919 appeared to confirm Einstein's prediction regarding the value of the light deflection, encouraged the belief that the gravitational red shift was implicit in the observed values of the solar red shifts; consequently, the latter were taken as resulting from a superposition of this predicted displacement upon the Doppler effects of radial currents in the solar atmosphere. The validity of this relativity-radial current interpretation is examined in Chapter II on the basis of observational data presently at our disposal. Our survey serves to show that, although many features of the solar red shifts can be explained by assuming that the steady state of the solar atmosphere is being maintained by a microscopic circulation associated with the solar granulation, the well-established observational fact that the absolute (Sun-arc) displacements are generally in excess of the relativity value at the edge of the disk (where the Doppler effects should vanish) is in contradiction to the conventional interpretation. This difficulty was fully appreciated by Professor Freundlich, who held the opinion that it might arise as a result of attempting to fit the observational data into a framework to which they did not rightly belong. It was this attitude which stimulated Freundlich (1954) to propose his revolutionary hypothesis that the red shifts observed in stellar spectra were produced as a result of some unknown interaction mechanism whereby light loses energy as it travels through space. Since this view did not appear to be compatible with the existence of the gravitational red shift, it was considered to be of the utmost importance to analyse the solar red shift data – which were much more reliable than those based on stellar observation – without taking it for granted that this effect existed, and determine whether the observed value supported Freundlich's interpretation. This was the original object of the present research, begun in September 1955. The major results of the initial two years' work carried out by the writer in collaboration with Professor Freundlich at the Department of Astronomy of St Andrews University are contained in the three reprints from the Annales d'Astrophysique which are submitted along with this thesis: they appear to confirm the validity of Freundlich's hypothesis, at the same time revealing no indication of the predicted gravitational red shift. Nevertheless, it was recognised that these conclusions were necessarily based upon a relatively small amount of observational material, and efforts were made by the writer to collect additional data with a view to investigating in more detail the observational properties of the solar red shifts, with particular reference to their dependency upon wavelength and excitation potential. Chapters III and IV are concerned with a description of the observational programme carried out with this intent at the Osservatorio Astrofisico di Arcetri, Italy, and the Universitäts-Sternwarte, Göttingen during the three-year period between October 1957 and September 1960. Much has happened during this time, however, which has cause us to reconsider the problem of the solar red shifts in an entirely different light. The present viewpoint is expressed in Chapter V.

The presence of inhomogeneities in semiconductor materials used to fabricate solar cell devices may result in spatial non uniformities in the device properties which may affect current generation in these devices. Besides, current reducing defects such as inclusions, local shunts and optical blockages may be introduced during the various device manufacturing processes which may adversely affect the performance and overall efficiency of solar cells. Diagnostic techniques are therefore needed to identify these defects so as to improve the production technology. This thesis presents the Light Beam Induced Current (LBIC) technique for mapping spatial non uniformities in solar cell devices. The LBIC is a non destructive characterisation technique that uses a focused light beam to raster scan a solar cell surface as the photo-generated current is recorded as a function of position to generate a photo-response map. The technique was used to obtain photoresponse maps for a mc-Si, Back contact Back junction (BC-BJ) silicon solar cell and the InGaP/InGaAs/Ge concentrating triple junction (CTJ) solar cell from which various local current reducing defects were mapped. A reflection signal detector was incorporated into the LBIC measurement system to enable us distinguish between optical blockages on the cell surface and current reducing defects within the solar cell devices. By dynamically biasing the solar cell devices, the electrical activity of the identified defects was investigated and also point-by-point current-voltage (I-V) characteristics were obtained. An interval division algorithm was applied to the measured point-by-point I-V characteristics to extract device and performance parameters from which device and performance parameter uniformity of the devices were mapped. Dark and full cell solar illumination I-V characteristics were also measured to extract device parameters. Analysis of extracted parameters revealed differences between extracted dark and illuminated device parameters which was attributed to departure from the superposition principle due to non-linearity of the semiconductor device equations with respect to carrier concentration. An investigation into the effect of illumination intensity on the I-V parameters of a spot illuminated BC-BJ Si solar cell showed a linear increase and a logarithmic increase of the short circuit current and open circuit voltage respectively with intensity while the series resistance decreased with intensity, which was attributed to increase in conductivity of the active layer. The ideality factor and saturation current were observed to increase while the shunt resistance initially increased before decreasing at higher intensity levels. Under monochromatic illumination, the photo-response of the BC-BJ Si cell was higher at 785nm than at 445nm due to low absorption coefficient of Si for longer wavelength radiations, resulting in carrier generation within the bulk, where there is a higher probability of carriers being collected at the p-n junction before they recombine. Under solar illumination, as the spectral content was altered using long pass colour filters with cut off wavelengths of 610nm and 1000nm, the performance parameters were observed to decrease and this was mainly due to decrease in intensity. For the CTJ solar cell, however, blocking of radiations below 610nm resulted in current mismatch that severely degraded the short circuit current (Isc). The current mismatch affected the extracted device and performance parameters. With a 1000nm long pass filter, a dark I-V was obtained since only the bottom Ge subcell was activated.

A simple empirical model to calculate solar spectral diffuse and global irradiance under cloudless skies was investigated. This formulation takes into account absorption of radiation by molecules such as O3, H2O and the uniformly-mixed absorbing gases CO2 and O2. Attenuation by Rayleigh-scattering and aerosol extinction are included. Aerosol attenuation is calculated through Angstrom's turbidity parameters α and β. The diffuse radiation is assumed to be composed of three parts: (1) Rayleigh-scattered diffuse irradiance; (2) aerosol-scattered diffuse irradiance; and (3) irradiance arising out of multiple reflections between the atmosphere and the ground. The global irradiance is the sum of these three components of diffuse irradiance plus the direct irradiance. The input parameters include an extraterrestrial spectrum, zenith angle θ, turbidity coefficient β, wavelength exponent α, ground albedo p , water vapor content and ozone content. The model is shown to yield very good results up to air mass two when compared to accurate theoretical calculations. No comparisons with measured spectra are presented because of a lack of accurate specifications of the input parameters. Results are presented to show the effect of variation of certain of the input parameters. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Thesis (M. Sc.)--York University, 1997. Graduate Programme in Earth and Space Science. / Typescript. Includes bibliographical references (leaves 83-85). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ27334.