Direct current energized pulse generator utilizing autogenous cyclical pulsed abnormal glow discharges

• US 5,502,354 A
• Filed: 04/19/1994
• Issued: 03/26/1996
• Est. Priority Date: 07/31/1992
• Status: Expired due to Term

• Current Assignee: Alexandra N. Correa, Paulo N. Correa
• Original Assignee: Alexandra N. Correa, Paulo N. Correa
• Inventors: Correa, Alexandra N., Correa, Paulo N.
• Primary Examiner(s): Pascal, Robert J.
• Assistant Examiner(s): Ratliff, Reginald A.
• Application Number:
  US08/229,931
• Time in Patent Office: 707 Days
• Field of Search: 315/111.11, 315/111.21, 315/111.01, 315/111.71, 315/111.91, 315/56, 315/61, 315/63, 315/339, 315/349
• US Class Current: 315/111.01
• CPC Class Codes: H01J 17/063 Indirectly heated cathodes, e.g. by the discharge itself
• CPC Class Codes: H01J 21/08 with movable electrode or electrodes
• CPC Class Codes: H01T 9/00 Spark gaps specially adapted for generating oscillations
• CPC Class Codes: H02M 3/15 using discharge tubes only

Abstract

A cold cathode vacuum discharge tube is used in a circuit for generating pulsed autoelectronic emissions which are particularly intense and frequent in the abnormal glow discharge region, and involve much lower current densities than predicted by the Fowler-Nordheim vacuum arc discharge region law. The discharge tube is characterized by a large electrode area at least of the cathode, and a large interelectrode gap. The electrodes are preferably spaced at least 2 cm apart in a parallel relationship. A probe may be introduced between the electrodes to reduce still further the field required to generate the emissions. In another configuration the probe forms the anode and two plates form cathodes. The circuit is driven from a direct current source of having an impedance sufficient to prevent establishment of a vacuum arc discharge.

Claims

1. A pulse generator comprising a cold cathode vacuum discharge tube having an anode and a cathode enclosed within an evacuated housing, wherein the cathode has an extended surface facing the anode and the cathode is capable of auto-electronic emissions under abnormal glow discharge conditions, which emissions have an extinction potential substantially higher than the sustaining potential of a vacuum arc discharge in the same tube, said discharge tube being connected in an external circuit comprising a continuous direct current source connected between the anode and the cathode, the external circuit being capable of delivering a potential sufficient to initiate auto-electronic emissions, and sufficient current at sufficient potential to drive said tube into a negative resistance region of abnormal glow discharge, the external circuit having an impedance sufficient that, as the tube is driven into said negative resistance region, potential between the anode and the cathode collapses below said extinction potential before a vacuum arc is established, whereby an endogenous cyclical pulsed abnormal glow discharge (PAGD) will occur, the cathode being of sufficiently robust construction to enable it to withstand sustained PAGD and erosion resulting therefrom without disruption or substantial thermionic emission, the surface of the cathode facing the anode being of a metal and having an area which promotes auto-electronic emission at much lower currents than predicted by the Fowler-Nordheim field emission theory, and the minimum separation of the cathode from the anode being at least about 2 cm.

2. A pulse generator according to claim 1, wherein the housing has an axis, and the tube further comprises:

a substantially pure tungsten probe disposed along the axis within the housing, the probe extending through a hermetic seal in a wall of the housing;

first and second electrodes disposed within the housing on opposite sides of the probe, the electrodes being suspended in parallel relationship and spaced apart by a minimum distance of 2 cm;

each electrode being respectively connected to an electrical lead which passes through a hermetic seal in a wall of the housing, at least one of said electrodes forming a cathode, and either the probe or the other electrode forming an anode.

3. A pulse generator according to claim 1, wherein the housing has an axis, and retains a residual gas atmosphere;

and the tube further comprises;

a probe disposed along the axis within the housing;

first and second electrodes disposed within the housing on opposite sides of the probe, the electrodes being in parallel relationship and separated by a distance of at least 3 cm;

electrically conductive means for respectively connecting the electrodes exterior to the housing to form the anode and the cathode;

and means for making an electrical connection with the probe from outside the housing.

4. A pulse generator as claimed in claim 3, wherein the probe comprises a first and second probe element arranged in a coaxial spaced-apart relationship, the first and second probe elements being spaced apart at least 2 cm.

5. A pulse generator as claimed in claim 1, wherein at least the cathode is a plate having an extended surface area facing the anode, and of at least about 0.5 mm thickness.

6. A pulse generator as claimed in claim 1, wherein the cathode is formed from aluminum or its alloys, tungsten, nickel and its alloys, zinc, iron or silver.

7. A pulse generator as claimed in claim 1, wherein both the anode and cathode are symmetrical and formed from the same metal.

8. A pulse generator as claimed in claim 1, wherein the anode is formed from tungsten.

9. A pulse generator as claimed in claim 1, wherein the tube is evacuated to at least 10 Torr.

10. A pulse generator as claimed in claim 1, wherein the tube is evacuated to at least 1 Torr.

11. A pulse generator as claimed in claim 1, wherein the housing encloses a residual gas atmosphere selected from argon, krypton, helium, neon, an inert gas mixture, air, oxygen, hydrogen and nitrogen.

12. A pulse generator as claimed in claim 1, wherein the tube has multiple cathodes.

13. A pulse generator as claimed in claim 12, wherein the cathodes are arranged symmetrically relative to a common anode.

14. A pulse generator as claimed in claim 1, wherein the cathode has an area of at least 64 sq. cm.

15. A pulse generator as claimed in claim 1, wherein the surface of the cathode facing the anode is a curved surface coaxial with the anode, which is rod-like.

16. A pulse generator as claimed in claim 1, wherein the cathode is planar.

17. A pulse generator as claimed in claim 1, wherein the tube has an anode to cathode spacing of at least 3.5 cm.

18. A method of operating a cold cathode vacuum discharge tube in a pulse generator, the tube having a metallic cathode with extended surface area facing an anode and spaced therefrom sufficiently to allow a plasma eruption from the cathode associated with an abnormal glow discharge to occur without reaching the anode to form a continuous vacuum arc discharge channel, the area and metal of the cathode being selected to promote low field emission at much lower current densities than predicted by the Fowler-Nordheim vacuum arc discharge region law, while withstanding repeated abnormal glow discharges without substantial thermionic emission, connecting a circuit including a continuous direct current source between the anode and the cathode, the source having an open circuit potential and initial current capacity sufficient to initiate an abnormal glow discharge from the cathode and drive the discharge tube into a negative resistance region of abnormal glow discharge, and an impedance sufficient to ensure that the potential across the tube falls below that necessary to sustain the abnormal glow discharge before a vacuum arc discharge can be established.