US3474281A

US3474281A - Electron beam production system for electronic discharge

Info

Publication number: US3474281A
Application number: US601623A
Authority: US
Inventors: Diether Vitzthum
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1965-12-23
Filing date: 1966-12-14
Publication date: 1969-10-21
Anticipated expiration: 1986-10-21
Also published as: DE1251876B; NL6615033A; GB1162108A; FR1505956A

Description

D. VITZTHUM Oct. 21, 1969 ELECTRON BEAM PRODUCTION SYSTEM FOR ELECTRONIC DISCHARGE Filed Dec. 14, 1966 ATTYS.

US. Cl. 313-337 6 Claims ABSTRACT OF THE DISCLOSURE An electron beam production system with heating of the main cathode, constructed as a dispenser cathode but not including a supply of emission substance or storage chamber therefor, by electron bombardment from an auxiliary cathode likewise constructed as a dispenser cathode.

The invention relates to an electron production system for electronic discharge vessels, in particular to an electron beam production system for HF power tubes, in which system a main cathode is provided at the end of an United States Patent G auxiliary electron discharge space, as an operating electrode, for the heating thereof through electron bombardment.

It is of particular importance for high power tubes operating with an electron beam, in tubes of such type, for example, traveling wave tubes with high power, an important difficulty resides in the necessity of maintaining the electrode which is required for the beam formation and which is immediately adjacent to the cathode sufficiently cool that it does not deliver any thermal emission when emission-promoting substances are vapor-deposited thereon. This requires a cathode with as low a filament power as possible, heretofore sought to be obtained, at the respective operating temperature by eifecting certain measures such as the utilization of a small volume for the reduction of the 'heat capacity, and of a small surface area for the reduction of the heat conduction, as well as by the utilization of a supporting structure of light weight and poor thermal conductivity for the reduction of the dissipation of heat.

It has already been proposed to heat the beam or main cathode of such an electron production system by cathodic bombardment from an auxiliary cathode disposed in an auxiliary electron discharge space and in this case to construct at least the main cathode as a dispenser cathode, in particular as an MK cathode.

The invention is directed to the reduction of the heat capacity of a dispenser cathode disposed at the end of an auxiliary electron discharge space and heated by cathodic bombardment by means of a special constructional arrangement to effect an increase in its heat economy.

In an electron beam production system of the type initially described, according to the invention this is achieved by the feature that there is provided a main dispenser cathode, in particular an MK (metal capillary) cathode, which does not possess its own storage chamber and supply, and the porous carrier disk for the emission substance which normally would close the chamber, receives its emission promoting substance as a basic part of the auxiliary cathode arranged therebehind and constructed as a dispenser cathode, in particular as an MK cathode, and its filament energy as a working electrode of the auxiliary discharge system.

Through extensive tests it has been ascertained that the quantity of emission promoting substance migrating from a normal capillary metal cathode towards the emis- 3,474,281 Patented Oct. 21, 1969 sion side during operation, i.e., the evaporation rate of, for example, barium, 1s completely sufiicient to activate a further porous emission substance carrier disk disposed in front of it, and which may even be larger, to a sufficient degree, for the emission function and to maintain it capable of emission during operation, in which arrangement, in contrast to heretofore existing concepts, it is not even necessary to construct this basic main cathode in such a manner that the pores of the emission disk are its largest openings.

In a practical example, the supporting cylinder of this sheet material or foil for the main cathode is so connected with the mounting enclosure for the auxiliary cathode by an insulating part to form a semi-closed container, that the two porous carrier disks for the emission substance of the two capillary metal cathodes approximately form the end closures of such space.

In this case the two mounting or supporting cylinders are especially advantageously constructed and arranged in such a manner and provided with such potentials that the occurring cathode bombardment achieves a uniform predetermined heating of the porous emission substance carrier disk of the main cathode.

One of the two mounting members or enclosures, or a further additional cylinder of thin sheet material coaxial to such member may also include an aperture diaphragm and parallel thereto, an apertured partition corresponding to a Wehnelt electrode may also be provided, by means of which the flow of electrons for the electron bombardment on the emission substance carrier of the main cathode may be regulated with respect to the cross section of the electron beam as well as with respect to the intensity, to permit a better adjustment of the desired operating temperature,

In especially advantageous manner, among other things in view of the technical arrangement, the porous emission substance carrier disk forming the main cathode may be mounted in such a manner that no completely closed space is formed between it and the following auxiliary cathode. The pores of the emission substance carrier disk in this case do not necessarily form the largest openings in the space existing between the two porous disks.

Since the height of the required operating temperature is essentially determinative for the filament power to be employed, an additional metal layer, for example out of a light or heavy platinum metal, may be applied as an emission base or surface upon the porous body, for example of tungsten, for the lowering of the temperature on the basis of a reduction of the electron atfinity.

Additional details of the invention will be explained in connection with the form of construction illustrated purely schematically in the drawing, which represents a longitudinal section of such a cathode system, in which parts which do not absolutely contribute to an understanding of the invention have been omitted or have not been designated.

The reference numeral 1 designates a carrier disk for an emission substance, having a relatively large surface which is represented, so to speak, as a basic part of a dispenser cathode, in particular an MK cathode, forming the main or beam cathode thereof. Such cathode possesses no supply of emission substance or storage space therefor, but instead is disposed at the end of an auxiliary discharge space as a working electrode thereof for the attainment of its necessary heating by a cathodic bombardment. For this purpose, its retaining cylinders 2, of thin sheet material, for example tantalum, may be connected through an insulating piece 3 with the extended portion of a mounting enclosure 4, also of thin sheet material, for the accompanying auxiliary cathode 6, like Wise constructed as a capillary metal cathode, in particular with its porous carrier 5 for the emission substance. The arrangement is such that between the two

carrier disks

1 and 5 for emission substance, as end members, a mechanically closed space is formed. However, in contrast to the above described arrangement, it will be apparent that the space between the main cathode and auxiliary cathode also may be open, and in an extreme case, the main cathode may, in ultimate form, consist of a porous disk. Consequently, for example, the insulating intermediate piece 3, instead of comprising a closed ring, may consist of individual pieces which bridge the space between the cylinders 2 and 4. The main cathode is activated in suflicient measure and maintained in operating condition by the emission-promoting substance. In addition, the applied potentials are so selected that the porous carrier disk 1 is loaded in the manner of a draw anode, as working electrode by the electrons of the auxiliary discharge system accelerated toward it and its proper heating during operation is thus provided in such manner.

Advantageously, an additional metal layer may be applied to the porous disk of the main cathode, which may, for example, be constructed of tungsten, to eifect a lowering of the temperature by means of a reduction of the electron afiinity, said layer comprising metal selected from the platinum group comprising platinum, cadmium and iridium.

Beside the small heat requirements of the main beam cathode, an importance advantage of the described electron beam production system resides in the reduction of the danger of vaporization on the principal electrodes, and in particular on insulating parts of the discharge vessel, with evaporating substances originating from the cathode, as well as the possibility of an especially simple construction.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

I claim:

1. An electron production system for electronic discharge vessels, in particular for power tubes, in the electron production system of which a main cathode is arranged as an operating electrode at the end of an auxiliary electron discharge space and heated by cathodic bombardment, comprising a main cathode constructed in the form of a dispenser cathode having a porous carrier disk from the front face of which the main electron beam is emitted, an auxiliary electron discharge space disposed behind said porous carrier disk, an auxiliary electron discharge system including an auxiliary cathode disposed in said space arranged to discharge electrons on the rear face of said main cathode, said auxiliary cathode also being constructed in the form of a dispenser cathode, operative to provide the emission-promoting substance for said main cathode which is received thereby as a basic part of such auxiliary cathode, said main cathode receiving its heater energy by cathode bombardment as an operating electrode of the auxiliary electron discharge system.

2. An electron production system according to claim 1, wherein said cathodes are individually supported by respective cylindrical members of thin sheet material, said cylinders and cathodes being arranged to form said auxiliary electron discharge space with said cathodes being disposed at opposite ends thereof, and insulating means disposed between and connecting the respective cylinders.

3. An electron production system according to claim 2, wherein said insulating means is cooperable with the respective cylindrical members and cathodes to form a closed discharge space. i

4. An electron production system according to claim 1, wherein means are provided for supporting said main cathode in operative position with respect to said auxiliary cathode, which means is so constructed that said auxiliary electron discharge space is not completely closed and the pores of the porous carrier disk of the main cathode do not form the largest openings in such space.

5. An electron production system according to claim 1, wherein the geometrical arrangement and construction of the electrodes of the system are such that with'predetermined operating potentials applied thereto, the cathodic bombardment eflects a predetermined uniform heating of the porous carrier disk of the main cathode.

6. An electron production system according to claim 1, wherein the porous carrier disk of the main cathode is constructed of tungsten and is provided with a layer of metal selected from the group consisting of osmium, iridium and platinum, which layer forms the emission surface of such cathode.

References Cited UNITED STATES PATENTS 2,830,917 4/1958 Kern 313-346 X 2,843,785 7/1958 Iversen 313-346 X 2,953,701 9/1960 Gale 3l3346 X 3,070,724 12/1962 Herbert et al. 313346 X 3,159,461 12/1964 MacNair 3 l3346 X 3,348,092 10/1967 Beggs 313-346 JOHN W. HUCKERT, Primary Examiner R. F. POLISSACK, Assistant Examiner U.S. Cl. X.R. 313-338, 346