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Biological response to ionizing radiation differs with radiation field. Particle type, energy spectrum, and dose-rate all affect biological response per unit dose. This thesis describes methods of spectral analysis, dosimetry, biological assays, and mathematical modeling for determining the relative biological response for low dose-rate fields. The spatial dimensions of optically stimulated luminescence dosimeters make them ideal for measuring dose at a specific location. However the response of these dosimeters varies with photon energy. A method is presented for measuring dose delivered by several fields with photon energies less than 60 keV using these optically-stimulated luminescence dosimeters. This method is confirmed using an ion chamber dosimeter and computer simulation. The construction of 24 Am irradiators for tissue culture and animal experiments using this dosimetr