Thesis (M.S.)--University of Michigan, 1958.

Thesis (M.S.)--University of Michigan, 1962.

In radiotherapy, half value layer has been accepted as a practical specification of the quality of primary x-rays. For the degraded radiation in a scattering medium, however, it is neither an applicable nor an adequate specification of the quality. This thesis describes a practical method of investigating the radiation quality in an irradiated medium. The method is based essentially on differences in emission and on differences in absorption of different materials. Two ratios were measured: (a) the ratio of the ionization current in a copper-lined ionization chamber to the ionization current in a lucite-wall chamber, (b) the ratio of the ionization current in the copper-lined chamber to the ionization current in the same lucite-wall chamber with the latter shielded by a copper absorber. These ratios, which depend on the spectrum of the x-radiation to which the chambers are exposed, change differently with change in spectrum and, therefore, give two indices of quality. For calibration purposes, the above ratios were measured for primary x-rays generated at different kilovoltages and with different filters. To investigate the quality of radiation in a scattering medium, the same ratios were measured and were compared with the results obtained for primary spectra. Radiation quality at different depths in water exposed to different qualities of primary x-rays was investigated. The results are in qualitative agreement with those obtained by previous workers. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The efficiency of a He³ filled ionization chamber for detecting neutrons via the He³ (n,p)T reaction was investigated to see if it would be feasible to use the instrument for measuring neutron flux. Calculations of wall loss showed that such measurements would in all probability not be very precise. Using neutrons with an energy of 2.76 Mev derived from the D(d,n)He³ reaction these calculations were born out. The efficiency of the detector was found to be ~0.9 x 10ˉ² % at 2.76 Mev, including the correction for the wall loss which amounted to 64% of the detected flux. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The threshold energy for the reaction Br⁸¹ (p,n)Kr⁸¹ was measured and found to be 1.133±.020 Mev. The threshold for Cd¹¹⁶(p,n)ln¹¹⁶ was searched for up to 1.8 Mev but was not found. The density of cosmic neutrons was measured at the earth's surface. It was found to be 4.2±.7x10⁻⁹ n/cm³ over land with 66% in thermal equilibrium. Over the sea, this density was 3.72±.98x10⁻⁹ n/cm³ with 64% in the thermal peak. The earth's albedo or reflectivity to neutrons impinging on it from the atmosphere was estimated to be .22. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Experiments are described on the possibility of developing a gas luminescence chamber for the observation of particle tracks. A brief review of devices currently available for obtaining ionizing particle tracks, particularly those capable of time resolutions in the microsecond region, is included. Attempts were made to detect scintillations in several gas and vapour mixtures. For some gas mixtures the possibility of using ionizing radiation to initiate a light producing chain reaction was investigated. These experiments were performed in the temperature range from 25 to 220° centigrade. Results obtained were not of such a nature to encourage further work towards the development of a gas luminescence chamber. As a background of non-radiation induced photon emission was observed for several reactions, it is possible that the methods employed in the experiment may be adopted to measure the onset and rate of some chemical reactions. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.