CHARACTERIZATION OF A REFRACTORY SURFACE AT A HIGH-TEMPERATURE APPLIED TO THE ZR-O W(100) SYSTEM - ON SELF-RECOVERY FUNCTION/

Surface characterization of the Zr-O/W(100) system, widely used as a h igh stability and high brightness cathode, was performed under operati ng conditions of (similar to 1710 K and similar to 10(-6) Pa) to bette r understand its electron emission characteristics. The combined surfa ce analysis techniques employed were Auger electron spectroscopy, ion scattering spectroscopy, high energy electron diffraction, and work fu nction measurement. This study has clarified the nature of the self-re covery function of the Zr-O/W(100) system as follows: excess Zr-O comp lex on the surface diffuses into the W-substrate during the initial pr ocedure of oxygen processing. These Zr-O complexes are then available to segregate to the surface to compensate for the deficiency of Zr ato ms, caused by ion bombardment from residual gases at similar to 10(-6) Pa during operation. This leads to the very high stability of the ele ctron emissivity. A model of the self-recovery function for oxygen ads orption is also proposed as an oxygen adsorption-deoxidization cycle a ppearing in Zr-O/W(100) under the operating conditions.