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A Poisoning Study of Nickel Matrix Cathodes.
DAYTON UNIV OHIO DEPT OF PHYSICS
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The poisoning of nickel matrix cathodes by various gases has been investigated experimentally. The experiments were performed using conventional UHV techniques. The emission current was measured as a function of time for cathode temperatures between 750 C and 1000 C and poisoning gas pressures in the range from .00000001 torr to .00001 torr. Oxygen, carbon dioxide and carbon monoxide poison these cathodes. For a fixed cathode temperature and poisoning gas pressure, oxygen poisons the cathodes most severely, carbon dioxide less so and carbon monoxide the least. The rate of poisoning for any of the gases increases with increasing poisoning gas pressure and decreasing cathode temperature. The experiments indicate that the time for reactivation from the poisoned state depends upon the length of time the cathode remained in the poisoned state. The poisoning and reactivation data will be compared with theoretical models of the poisoning process. Author
APPROVED FOR PUBLIC RELEASE