If the cathode is to be stored for a period of more than a

few months before or after it is used, we recommend that

it be left in the shipping jar and stored in a clean, dry

environment such as a vacuum desiccator or a nitrogen



Do not remove a cathode that has operated for more than

50 hours in a system with the intention of reinstalling it

at a later date. During use lanthanum rich zones are

formed on the shank of the crystal adjacent to the carbon

blocks. If the cathode is removed from the vacuum into

air, these zones can oxidize. La2O3 is an insulator;

therefore the resistance across the emitter can become

high enough that it is no longer possible to adequately

heat the cathode. In this case, the cathode must be



Technical Information

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