AVS 45th International Symposium
    Vacuum Technology Division Monday Sessions
       Session VT-MoP

Paper VT-MoP1
Behavior of the Negative Collector Current in Ionization Vacuum Gauges

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Vacuum Technology Poster Session
Presenter: K. Kokubun, Electrotechnical Laboratory, Japan
Authors: K. Kokubun, Electrotechnical Laboratory, Japan
M. Hirata, Electrotechnical Laboratory, Japan
Correspondent: Click to Email
In or near XHV pressure region, negative collector currents have been observed in the Extractor vacuum gauges that several times experienced a baking at 573 K for about 70 hours.@footnote 1@ It was found that the negative collector current continued to flow even when the gauge was not in operation. Authors confirmed that in these gauges a negative electromotive force of - 1 V to - 100 mV was formed in the system including the collector electrode and the gauge body, and simultaneously the insulation of the collector electrode degraded due to unknown causes. These results suggested that some new structure was formed in the gauge head system by the bakings. This conjecture was supported by measuring the temperature dependences of the negative collector current, the negative e.m.f., and the insulation resistance. These temperature dependences were remarkably different from those of a normal gauge. Especially, the insulation resistance drastically increased to about 330 K, and then abruptly decreased. This behavior was in strong contrast to that of the normal gauge. On the other hand, in the normal gauge a significantly larger positive e.m.f. was observed. But it was found that only a small positive current flowed because of the very large insulation resistance of the collector electrode. @FootnoteText@ @footnote 1@K.Kokubun and M.Hirata, J. Vac. Soc. Jpn, 40, 137(1997).