Cathode comprising a substrate (2) supporting a cathode emissive coating,
comprising what is called an emissive central zone (12) and what is called
a nonemissive peripheral zone (11); according to the invention:
- the average density and the emissive zone (12) is greater than
that in said nonemissive zone (11),
- the average thickness in the emissive zone (12) is less than
that in the nonemissive zone (11).
In this way it is possible to significantly limit the drift in cut-off voltage,
while still maintaining good maximum emission performance in DC mode and in pulse mode.
