A method and apparatus for operating a multi-hot-cathode ionization gauge
is provided to increase the operational lifetime of the ionization gauge
in gaseous process environments. In example embodiments, the life of a
spare cathode is extended by heating the spare cathode to a temperature
that is insufficient to emit electrons but that is sufficient to decrease
the amount of material that deposits on its surface or is optimized to
decrease the chemical interaction between a process gas and a material of
the at least one spare cathode. The spare cathode may be constantly or
periodically heated. In other embodiments, after a process pressure
passes a given pressure threshold, plural cathodes may be heated to a
non-emitting temperature, plural cathodes may be heated to a lower
emitting temperature, or an emitting cathode may be heated to a
temperature that decreases the electron emission current.