Study of elimination of vapor atom deposition. Final report

The major objective of this study was to define and evaluate methods by which an optical system could be protected from performance degradation arising from exposure to a beam of heavy metal atoms. The optical system is coupled to a chamber in which the metal atoms are being produced and processed. The coupling aperture is the source of the contaminating metal atom beam, which, if un-attenuated, would degrade the system performance in an unacceptably short period of time. It was agreed early in the program to concentrate on a gaseous scattering technique, with a stated objective of metal beam flux reduction of about 10/sup 6/. Additional constraints require that the scattering gas must not effuse back into the main process chamber at such a rate that it has significant effect on the vacuum level in the chamber, which is of the order of 10/sup -6/ torr; finally, the path length between the main chamber and the optical system must not be increased unduly. This report summarizes the analyses that were performed under the program. Section 2 presents a summary review, while the details of the analyses are described in Section 3. Recommendations leading toward final system design are given inmore » Section 4. Finally, an appendix contains a description and printout of a program that was developed and used to facilitate the evaluation of system performance parametrically. 6 refs., 9 figs.« less