SIMILARITY RULES FOR LOW-PRESSURE GAS DISCHARGES IN A METAL + RARE GAS MIXTURE

The similarity rules for plasma characteristics of low-pressure metal vapour (Hg, Cd, Zn) + rare gas discharges are derived in this paper. According to the new similarity rules the number of independent external parameters which are necessary to describe internal plasma characteristics is less than the known rules give. The similarity of nonstationary discharges is experimentally investigated. The low-pressure Hg+ rare gas discharge is ofgreat The purpose of this work is to derive, inmore gen-interest because of its practical application (fluores- era! form than has been obtained in refs. [4,5], the cent lamps) and, to a considerable extent, because of similarity rules for internal plasma characteristics of the different roles that mercury and rare gas atoms the gas discharge in the melt vapour (Hg, Cd, play in the positive column. In a wide range of dis- Zn) + noble gas mixture and to consider the simi-charge conditions the noble gas defines transfer pro- larity of the nonstationary discharges. The likeness cesses of particles onlyand the mercury is responsible ofthe atomic structure and similar cross-sections for for the ionization processes and the energy losses of the ionization and the excitation ofHg-, Cd-, and Zn-electrons in the plasma. This makes it possible by atoms allows us to considerall these plasmas in the varying discharge conditions to change some plasma limits of the common model [5]. characteristics without essential influence on others. To find the similarity rules which are to be fol