Abstruct-Isotope separation has many important industrial, medical, and research applications. Large-scale processes have typically utilized complex cascade systems; for example, the gas centrifuge. Alternatively, high single-stage enrichment processes (as in the case of the calutron) are very energy intensive. Plasmabased methods being developed for the past 15 to 20 years have attempted to overcome these two drawbacks. In this review, six major types of isotope separation methods which involve plasma phenomena are discussed. These methods are: plasma centrifuge, AVLIS (atomic vapor laser isotope separation), ion wave, ICR (ion-cyclotron resonance), calutron, and gas discharge. The emphasis of this review is to describe the plasma phenomena in these major categories. An attempt was made to include enough references so that more detailed study or evaluation of a particular method could readily be pursued. A brief discussion of isotope separation using mass balance concepts is also carried out.
Several surface analytical techniques, including electron spectroscopy for chemical analysis (ESCA)(X-ray photoelectron spectroscopy) and sputtered neutral mass spectrometry (SNMS), were used to study the interaction between Hg and other components of fluorescent lamps, a very critical issue in lighting industries. Active sites, responsible for Hg interaction/deposition, can be successfully identified by comparing the x- y distribution (obtained by ESCA mapping) and depth distribution (available through SNMS) of respective lamp components with that of Hg. A correlation in both depth and x- y distribution is strong evidence of site preference for Hg interaction/deposition. A burial mechanism is, however, proposed when only depth distribution, not x- y, is correlated. Other modes of ESCA (high resolution, angle-resolved, etc.) were also helpful. Information about the valence states of the interacted Hg species would help to define the nature of the interaction.
ExperimentalInstrumentation.-ESCA was performed using a Physical Electronics 5702 ESCA/Auger spectrometer. Samples were bombarded with X-rays from a standard source using the aluminum K␣ anode. The anode was energized to 15 kV and 400 W. Binding energies The interaction between Hg and components in fluorescent lamps was studied using electron spectroscopy for chemical analysis (ESCA) and sputtered neutral mass spectrometry (SNMS). Active sites, which were responsible for Hg interaction/deposition, were identified by comparison of the X-Y distribution (obtained by ESCA mapping) and depth distribution (available through SNMS) of respective lamp components with that of Hg. These results showed that Hg strongly interacted with Na (from glass) and the emitter components, especially Ba. In the case of lamps with a tin oxide conductive film, the film was also a source for interaction. Exact assignment of the oxidation state for the interacted Hg species was not certain due to a small variation in binding energy shift among the Hg compounds. However, the data suggested an Hg(0) state. It was possible that most of the Hg species strongly chemisorbed onto Ba (and/or Sr) and Na sites or formed intermetallic compounds with these elements. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.215.17.190 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.215.17.190 Downloaded on 2015-06-15 to IP
The efficiency of a mercury-rare gas electrical discharge, which forms the basis of a fluorescent lamp, can be increased about 5 percent simply by increasing the concentration of mercury-196 from 0.146 percent (natural) to about 3 percent. These findings can be implemented immediately without any significant change in the process of manufacturing of this widely used source of illumination, provided that mercury-196 can be obtained economically. The potential energy savings for the United States are estimated to be worth in excess of $200 million per year.
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