SCANNING AUGER MEASUREMENTS OF ACTIVATED AND SPUTTER CLEANED RE-COATED SCANDATE CATHODES

The effect of sputtering and Sc supply rate for Re-coated scandate cat hodes is investigated by scanning Auger measurements (SAM) and electro n emission measurements. It is shown that during the first few hours o f operation, the Sc supply rate is sufficiently high to recover from t he ion bombardment. However, after several hours of operation the Sc s upply rate is unmeasurably low and permanent damage shows up in the Sc intensity as well as in the electron emission current density. The cu rrent density of Re-coated scandate cathodes does not drop to the valu e of Re-coated cathodes without Sc2O3. It will be shown that this resu lts from the roughness of the evaporated Re-surface which accounts for a reduced sputter efficiency. This offers the possibility of improvin g the performance of these cathodes in applications such as CRT's.