Low dose and low dose rate fields constitute the majority of radiation exposure scenarios in radiation protection. Conversely, very little epidemiological or physical data are available at these levels. This situation exists because the parameters characterizing low dose and low dose rate environments are difficult to assess at cellular levels where the fundamental biological effects from radiation insults occur. The quantities required for a complete biological assessment are the distribution of energy deposition in biological targets and the cellular response to such insults. A new detector to measure physical energy depositions on nanometer scales was developed in this thesis. A computational tool was also developed to calculate clustered distributions of energy deposition from electrons and photons.; A dosimeter has been developed which characterizes energy depositions from charged particles in nanometer dimensions. The dosimeter is a threshold-type detector based on the temperature response of the superheated liquid droplet detector (SLDD). SLDDs based on Freon-115 have been designed and tested. A data acquisition system that measures the acoustic signals from bubble nucleation events has been developed.; An original electron track code, ESLOW3.1, has been developed. The code simulates electron tracks on an event-by-event basis down to an absolute minimum of 20 eV. The transport medium is water vapor. The cross sections have been compared with published data and theoretical models where available. Trial calculations of pertinent quantities are in good agreement with published results.; A new operational quantity, the cluster spectrum, given the symbol {dollar}c(varepsilon),{dollar} has been defined. This quantity is measured by the SLDD operated in nanodosimetry mode. The performance of the SLDD has been tested with a {dollar}sp{lcub}60{rcub}{dollar}Co point source. The effective measurement range of the nanodosimeter is between 60 and 500 eV of energy deposition. Measured values of {dollar}c(varepsilon){dollar} are compared to track structure calculations. The comparison shows good agreement between estimated and measured results.
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