Masters Theses

Date of Award

8-1988

Degree Type

Thesis

Degree Name

Master of Science

Major

Nuclear Engineering

Major Professor

Paul N. Stevens

Committee Members

D. A. Rasmussen, B. R. Upadhyaya, P. F. Pasqua

Abstract

The procedure for the spectral calibration of the Advanced Toroidal Facility (ATP) spatial multipoint Thomson scattering electron density and temperatiffe diagnostic has been modified in order to make the calibration less time consuming. The scattering system incorporates a light collection arrangement which focuses light onto fifteen different spectrometer input slits via optical fiber bundles. Each spectrometer corresponds to a different spatial location. The spectral calibration is used for the comparison of spectrometer channel efficiencies, and is a necessary step in order to achieve accurate determinations of temperature with the Thomson scattering system. A white plate, which is illuminated by a standardized lamp, has been incorporated into the system. This enables the entire vertically arranged optical fiber image plane to be illuminated. Thus, all of the spectrometer input channels can simultaneously receive the standardized light. In order for this light to reach the image plane, it is necessary to transmit the light through the Thomson scattering collection lens. Light from the white plate is received by the image plane out of focus due to geometrical constraints. This will also ensure that irregularities of the white plate will not be imaged onto the image plane. In order that all channels would receive sufficient light, a commercial optics code (ACCOS V) was used to help design the white plate, its light source, and the optimal placement of these components with respect to the viewing lens. Photometric measurements using pulsed photomultiplier tubes were performed so as to verify the photon inventories of the computer modeling. The experimental inventories were within 32% of the modeled inventories, which satisfied the goal of an "order of magnitude" approximation. Data aquisition is accomplished via CAMAC linked to a VAX computer. I V Simple fortran codes were developed and used to perform a wavelength calibration of two separate spectrometers. The spectral calibration of the same two spectrometers was carried out using a special test-spectral calibration code. Finally, the generated calibration constants (which relate energy scattered into a channel with the integrated signal) were statistically analyzed and their uncertainties compared with that predicted by "photon statistics". The results indicated that calibration constants could be calculated with an uncertainty within about 2%, consistant with photon statistics.

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