Three different types of radiometry have been examined to find the best type for solar spectral irradiance measurements requiring long-term (22 years) and ultra-high precision (0.1% uncertainty) in the near-UV, visible, and near infrared. It has been determined that the best radiometry uses the self-calibration technique developed at NBS using laser lines. Normalization techniques were applied to silicon reflectivity and quantum efficiency models for use with thermal sources and grating spectrometers. The results compared with similar laser-source calibration showed disagreement less than 0.1%. Germanium and GaAsP detectors were also investigated in the infrared and deep blue wavelengths. The germanium detector showed significant recombination loss of photogenerated carriers due to the ion implantation fabrication process. GaAsP detectors have very small dark currents ( < 1 nA), but also demonstrate significant recombination losses inside the photodiode. The possible loss mechanism of the Ge and GaAsP detectors are suggested for future study.

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A versatile solar spectroradiometer has been designed which is capable of measuring direct solar radiation, the solar aureole, and sky radiance far from the sun. An active tracker consisting of a quadrant detector, telescope and stepper-motor driven alt-azimuth mount is used to position the spectroradiometer by computer control for solar tracking and almucantur scans. An internally baffled telescope designed to suppress stray light is employed as the optical receiver, and a photodiode serves to convert the collected flux to an electrical signal. A digitally controlled gain-switching transimpedance amplifier is used to scale the photodiode output to accommodate the large signal range encountered between measuring direct solar radiation and sky radiance well away from the sun. Example measurements are presented which demonstrate the system's capabilities.

Scanning surveys of building surfaces and land areas are performed with radiation detection equipment to identify areas of elevated radioactivity. To quantify the extent and magnitude of the contamination, follow-up radiation surveys and soil sampling are usually required. The ability to accurately quantify discrete locations or "hot particles" of contamination requires a full understanding of the scanning detection efficiency of the instrument being used. A cylindrical sodium iodide detector's scanning detection efficiency was examined theoretically using the Monte Carlo N-Particle Code, version 4b, and examined experimentally using the Marianno Research Sled located in the Department of Nuclear Engineering, Oregon State University. A method is described for predicting instrument scanning detection efficiency for a 1 s observation interval over a range of scanning speeds using a series of static detection efficiency measurements. Testing of the prediction method and accuracy of predicted values was performed by comparison to experimentally determined values of scanning detection efficiency. Additionally, the validity of the predicted scanning detection efficiency values was tested by quantifying a radioactive source at a number of scanning speeds to quantitatively determine its activity. Activity values determined by scanning the source were compared against an activity value determined a by high purity germanium detection system. Results indicate that the method is both easy to perform and provides statistically accurate scanning detection efficiency values that can be utilized for the quantification of discrete locations or "hot particles" of radioactive contamination. / Graduation date: 2002

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No description available.

No description available.

No description available.