Electric lamp and discharge devices – With gas or vapor – Having hollow cathode
Patent
1987-07-28
1989-12-05
Yusko, Donald J.
Electric lamp and discharge devices
With gas or vapor
Having hollow cathode
313632, 313613, 313614, 313605, 313606, 313590, H01J 6109
Patent
active
048855049
DESCRIPTION:
BRIEF SUMMARY
This invention relates to hollow cathode assemblies, particularly but not exclusively when mounted within an envelope to form a boosted discharge hollow cathode lamp.
A prior-described form of boosted discharge hollow cathode lamp comprises an open-ended cylindrical cathode of the element selected to characterize the lamp, supported centrally within a glass envelope. An anode is spaced from one of the open ends of the cathode and an electron emitter has its outlet aperture adjacent and to the side of the other open end. This lamp is a modification of an earlier boosted discharge lamp in which an electron emitter directed a stream of electrons above and across the open top of a cup-shaped electrode. The purpose of the electron stream was to boost the proportion of atomic species which attained an excited energy state. The later lamp, in which the electron stream passes through the cathode to the anode, has been more successful in achieving this object but is expensive to manufacture because of the requirement for multiple insulating baffles about the cathode to isolate the cathode support structure and associated current conductors. Such baffles are necessary to prevent discharge from surfaces other than the interior of the cathode, for example from the external cylindrical surface of the cathode and the exposed surfaces of the support structure. Such extraneous discharges sputter contaminating species into the neon/elemental vapour.
The present invention is based upon the realization that the stream of electrons passing through the cathode from the electron emitter to the anode is capable alone, if at an adequate level, of confining surface discharge to the interior of the cathode.
The invention accordingly provides a hollow cathode assembly comprising a hollow cathode, open at spaced apart ends, formed of a selected element which characterizes the assembly, means supporting the hollow cathode, an anode spaced from one of said open ends of the cathode, electron emission means with its outlet spaced from the other open end of the cathode, and means to constrain the electron stream from said emission means to the anode to pass through the cathode, wherein said cathode support means is not isolated to prevent surface discharge therefrom but in operation of the lamp the stream of electrons from the electron emission means through the cathode to the anode substantially confines surface discharge to the interior of the cathode.
The invention further provides a boosted discharge hollow cathode lamp comprising an outer transparent envelope usually filled with an inert gas, and, within the envelope: which characterizes the lamp; the cathode; and pass through the cathode; discharge therefrom but in operation of the lamp, by application of a sufficient voltage between the cathode and anode to generate a discharge for causing cathodic sputtering of said element, the stream of electrons from the electron emission means through the cathode to the anode substantially confines surface discharge to the interior of the cathode.
Preferably, said anode is disposed within an inner envelope which is typically transparent and has an open end in close proximity to said one open end of the cathode. Advantageously, this open end of the inner envelope is dimensioned to provide an annular opening from the interior of the inner envelope about the hollow cathode, which annular opening is small enough to act as an insulator to substantially prevent discharge occuring around the cathode.
There may be further provided within the envelope one or more electrical conductors in electrical contact with the cathode, either directly or indirectly, which conductors are likewise not isolated to prevent surface discharge therefrom, since the stream of electrons from the electron emission means to the anode substantially confines surface discharge to the interior of the cathode.
The invention will be further described, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is a side elevation of a boosted discharge hol
REFERENCES:
patent: 1841289 (1932-01-01), Jenks, Jr.
patent: 1888670 (1932-11-01), Hotchner
patent: 2457891 (1949-01-01), Henninger et al.
patent: 2473833 (1949-06-01), Stutsman
patent: 3855491 (1974-12-01), Yamasaki
patent: 4339691 (1982-07-01), Morimiya et al.
patent: 4698550 (1987-10-01), Kobayashi et al.
Author: Lowe, "A High Intensity Hollow Cathode Lamp for Atomic Fluorescence"; Spectrochimica Acta.; vol. 26B, 12-1971, pp. 201-205.
Horabik Michael
Photron Pty. Ltd.
Yusko Donald J.
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