Method of stabilizing emitted electron beam in field emission electron gun
AssigneeHitachi, Ltd.
InventorsSatoru Fukuhara, Shigehiko Yamamoto, Hiroshi Okano
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Abstract
A stabilizing method is provided wherein a field emission cathode is subject to heat treatment of 2,000.degree.C. to 3,000.degree.C. in a hydrogen gas atmosphere of 1 .times. 10.sup..sup.-9 Torr to 5 .times. 10.sup..sup.-7 Torr and hereinafter an electric field in excess of 10.sup.7 volt/cm is applied to the cathode, whereby the emitted electron beam current from the cathode can be maintained constant for a long time.
Claims10
A method of stabilizing the emitted electron beam in a field emission electron gun comprising a first step of introducing an amount of hydrogen gas into a vacuum vessel containing a field emission cathode tip to a partial pressure of 5 .times. 10.sup.-.sup.7 to 1 .times. 10.sup.-.sup.9 Torr, and a second step of effecting heat treatment of the cathode tip.
In a method of stabilizing an electron beam emitted from the cathode of a field emission electron gun, wherein said cathode is disposed in an ambient vacuum having a low pressure, the improvement comprising the steps of:
- a. introducing hydrogen gas into the ambient vacuum in which said cathode is disposed to a partial pressure of 5 .times. 10.sup.-.sup.7 to 1 .times. 10.sup.-.sup.9 Torr;
- and
- b. heating said cathode at a temperature within a prescribed temperature range sufficient to remove impurities deposited on the cathode surface but insufficient to cause said cathode to melt, whereby hydrogen gas introduced in step (a) will be absorbed by said cathode and stabilize said electron beam emitted therefrom.
Dependencies are inferred from the claim text.