Optogalvanic Spectroscopy and Cataphoretic Laser Isotope Separation

Citation

Gabriel, Andrew Keith (1981) Optogalvanic Spectroscopy and Cataphoretic Laser Isotope Separation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/xhjf-aa40. https://resolver.caltech.edu/CaltechTHESIS:09282010-100527331

Abstract

A microscopic theory for the positive column discharge (PCD) is developed using rate equations and power balance equations to model the microscopic discharge processes. Macroscopic variables are calculated from the microscopic parameters. The model is used to characterize a hydrogen-helium PCD.

The equations in the model are modified to account for the presence of resonant (H-alpha) radiation from an external source. The model is then used to predict the voltage change in a hydrogen PCD (the optogalvanic effect) as a function of current, illumination intensity, and gas pressure. The results compare very favorably with experiments conducted to measure the OGE.

Transient voltage changes induced by resonant illumination in a PCD are calculated by numerical integration of the model equations. Perturbation theory is applied to the equations to obtain more physical insight into the physics of the transient OGE.

The experimental apparatus used to measure the OGE and that used to measure the electron temperature (double probes) are described. A discussion of experimental problems covers some of the difficulties encountered.

The PCD model and OGE model are used to evaluate the practicality of separating hydrogen and deuterium by optically assisted cataphoresis in the PCD.

The possibility that recombination is a dominant process in the discharge is discussed in detail and rejected.

A careful description of the interaction of the illuminating radiation and the PCD plasma is given, with special attention to homogeneous and inhomogeneous broadening processes, saturation of absorption and saturation of the OGE, and the relative bandwidths of the illuminating radiation and discharge gas.

Some suggestions are made for future work.

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