US2687488A

US2687488A - Gas tube construction

Info

Publication number: US2687488A
Application number: US316425A
Authority: US
Inventors: Lawrence J Giacoletto
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1952-10-23
Filing date: 1952-10-23
Publication date: 1954-08-24
Anticipated expiration: 1971-08-24

Description

Aug. 24, I954 J. GIACOLETTO GAS TUBE CONSTRUCTION Filed Oct. 23, 1952 4 2. .u. a v v 4 a 4 a 2. a a. 2 0 v I. M Q. 0 x .2 w 2 r Wm M Mr? m C N W W. M.

WFMU ORNEI Patented Aug. 24, 1954 GAS TUBE CONSTRUCTIQN Lawrence J. Giacoletto, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 23, 1952, Serial No. 316,425

Claims. 1

This invention relates to electron discharge devices of the type in which an ionizable medium is employed to support a discharge. In particular, this invention relates to such devices in which a control electrode may continuously control or modulate the current through the device at a very high rate.

In an article appearing in IRE, volume 40, number 6, June 1952, page 645, by Malter, Johnson, and Webster, gas discharge devices are described which can be used in applications in which prior art gas tubes have been unsatisfactory or could not be used. As is pointed out in the above identified article, this type of discharge device separates the functions of (1) ionizing the tubes ionizable medium and (2) providing a path for the load current through the tube.

The type of tubes with which this invention relates normally includes 1) a group of auxiliary electrodes, comprising an auxiliary cathode surrounded by an apertured electrode, to provide an auxiliary discharge and thus ionize the medium; and (2) a group of main electrodes comprising a main thermionic cathode, a control electrode and an anode. Although this general type of discharge device has offered many advantages it has, prior to this invention, had certain structural limitations. One of the structural limitations of this type of discharge device has been the requirement of two cathode heaters to heat the two cathodes.

A further structural limitation of this type of discharge device has been that the positive ions formed by the auxiliary discharge are not efliciently nor effectively directed into the main current path. This disadvantage has made necessary the generation of a greater number of positive ions.

It is therefore an an object of this invention to provide a new and novel gas discharge device of the type described that overcomes the above mentioned disadvantages.

Another object of this invention is to provide a new and novel gas discharge device of the type described that effectively and efiiciently utilizes the ions formed by the auxiliary discharge.

A further object of this invention is to provide a new and improved gas discharge device of the type described that utilizes a single heating element to heat both the auxiliary and main cathodes.

A still further object of this invention is to provide a new and improved gas discharge device of the type described that contains cylindrically shaped and concentrically placed elements and thus is easier to manufacture.

These, and other objects, have been accomplished in accordance with the general aspects of this invention by providing a concentric arrangement of electrodes including a single centrally located heater element. The single heater element is surrounded by a control electrode and an anode. Intermediate the control electrode and the heater element there is provided an apertured cathode having a coating of thermally heated electron emissive material thereon. Immediately surrounding the heater element there is an electrode which is in one embodiment an auxiliary cathode, and in another embodiment is an auxiliary anode. The single heater element heats the electrode which in turn heats, by radiation, the apertured cathode and the desired emission occurs.

These and other features and advantages will best by understood from the following descriptions of the illustrated embodiments when read in connection with the accompanying drawings wherein like reference characters designate similar parts throughout the several views and in which:

Figure 1 shows a sectional view in elevation of an embodiment of a gas discharge device constructed in accordance with this invention;

Figure 2 is a sectional view taken along line 2-2 of Figure 1;

Figure 3 is a sectional View in elevation of a further embodiment of a gas discharge device constructed in accordance with this invention; and

Figure 4 is a sectional view taken along line 44 of Figure 3.

Referring now more particularly to Figures 1 and 2, the gas discharge device includes an envelope 8 having an ionizable medium therein. Any suitable gas or mixture of gases may be utilized as the ionizable medium. The gas pressure for any particular embodiment will be in accordance with its specific electrode geometry and spacing but is not at all critical and may be varied over wide ranges. A number of tubes of the type under consideration have been found to operate satisfactorily with a filling of helium at a pressure of approximately 750 microns. However, as is well known, other gases and other pressures may be used.

The electrode assembly includes two groups of electrodes, the electrodes for ionizing the medium, and the electrodes included in the load 01' Work circuit. The group of electrodes for ionizing the medium includes an auxiliary cathode Hl, and the heating element l2. The auxiliary thermionic cathode I is an indirectly heated, oxide coated cathode of the conventional type. Surrounding the auxiliary cathode iii are the load circuit group of electrodes. The load circuit group of electrodes includes an apertured, or perforatedpmain cathode l4;"a control clestrode l6, and an anode l8 spaced in that order.

All of the electrodes are supported in the envelope in a conventional manner by means of support rods l9 and by the two and insulating members 29 and 2|. The main apertured, or perforated, cathode is coated'with any of the Well known thermally activated electron emissive materials 22. The emissive material may be coated on apertured main cathode by-any of the well known means, such as spraying and it may be coated on both sides or only on the side adjacent the control electrode [5. The entire electrode structure and theend insulating members 20 and 21 are supportedbythe re-entrant stem, as shown, and are energized in a conventional manner.

In operation of the device, the single heater l2 will supply a sufiicient amount of thermal energy both to the auxiliary cathode l2, and to the apertured main cathode i ito heat the electron emissive materials to cause electron emission. The heat is transferred by radiation between the two cathodes. A potential is applied to the auxiliary cathode K! that is negative with respect to the apertured main cathode l4. The difierence in potential existing between auxiliary cathode IG and apertured main cathode-Iii is greater than the ionization potential and may be approximately 100 volts. Due to this difference-in potential, the electrons emitted by-the auxiliary cathode ii) are attracted to the apertured main cathode l4 and ionize the medium as they progress from the auxiliary cathode-l0 to the apertured main cathode [4. These ions-diffuse outward through the apertures of main cathode I4 and form a plasma for themain discharge'between the main cathode M-andtheanodelt; The difference of potential between the apertured maincathode M and the main anode l8, i. e. the main current electrodes, is normally less than the ionization potential of the medium'and may be approximately 20 volts; Control electrode [6 normally is negative with respect to anode l3 and may have a signal'applie'dthereto; Control electrode 16 controls ithe'main. current in a manner as is more fully explained inthe aforementioned article.

Referring nowto Figures 3 and 4, there is shown a gas discharge device comprising a sealed envelope 9 having an ionizable medium therein. The electrode structure'includes a concentric array of a heater element 28; an auxiliary anode 26, an apertured 0r perforated cathode 39, a control electrode 32;and ani'anode 34 arranged in that order with the heater element 28 being centrally located. The electrodes are supported by'support rods 35 and end insulating members 37 and 39' as described in connection with Figures 1 and 2.

The apertured, or perforated, cathode 3!) is coated on both sides witlra thermally activated electron emissive material-3|: Any ofthe well known electron emissive coatings will be suitable as will be any of the-conventional methods of applying the electron emissive coating. The side of the apertured cathodetc adjacent auxiliary anode 26 acts as an auxiliary cathode, and the emissive material is thermally activated by means of the radiant heat energy from the heater element 28. The side of apertured cathode 30 adjacent control electrode 32, since it is also coated with electron emissive material, will also act as a cathode but this side of the apertured cathode 353 will function as a main cathode for the main group of electrodes. The control electrode 32 and main anode 34 are similar to those described in connection with Figures 1 and 2, so that further description is not deemed necessary.

In operation of the embodiment of the invention shown in Figures 3 and 4, auxiliary anode 26 is heated by means of the heater element 28. The auxiliary anode 2B is also electrically energized so that it is positive with respect to apertured cathode30 by means of the connection through resistor All to source 36. When desired resistor ill may be connected to a tap on source 36. The apertured cathode 38 may be at ground potential, as shown, if desired. As in conventional structures, main anode S lls positive with respect to apertured cathode so by being connected through load 38 tosource 35, and a signal may be applied to control electrode 32 as shown. It

should be noted that the device is completely connected while using only a single source 36. The heater elements 23 may also be connected to this source if desired by conventional taps on the source 38.

The heat from heating element 23 heats the auxiliary anode 25 which in turn radiates heat to apertured cathode 39 so that the electron emissive material is heated. Thus electron emission occurs from both sides of the apertured cathode St. the apertured cathode are attracted toward the auxiliary anode 2E and will cause ionization in this region. The positive ions that are formed by this ionization are repelled from the auxiliary anode 2t and travel out through the apertured cathode 3! into the main current path and thus form a plasma in this region. The electrons from the outside or apertured cathode 38 are, because of the attraction of main anode 3t, attracted toward the main anode 3t and may be modulated as explained in the above identified co-pending application.

This invention should not be limited to the method of connecting the various elements that are shown in Figure 4 for this diagram i given merely to show a method of connecting the tube so that only one power supply is required. It

should be understood that conventional circuits may also be utilized.

I claim:

1. A gas-discharge device, comprising a sealed envelope having an ionizable medium therein, a heater element, an array of electrodes including an electrode, an apertured indirectly heated thermionic cathode, a control electrode and an anode spaced in that order from said heater element and within said envelope.

2. A gas discharge device, comprisin a sealed envelope having an ionizable medium therein, a single heater element, an array of electrodes including an electrode for afiecting charged particles of said medium, an apertured indirectly heated thermionic cathode, a control electrode and an anode spaced in that order from said heater element and within said envelope.

3. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, a single heater element, a concentric array of electrodes including an electrode for afiecting charged The electrons emitted from the inside of particles of said medium, an apertured indirectly heated thermionic cathode, a control electrode and an anode spaced in that order around said heater element and within said envelope.

4. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, a single heater element, an array of electrodes including an electrode for afiecting charged particles of said medium, an apertured indirectly heated thermionic cathode, a control electrode and an anode spaced in that order within said envelope, said single heater element being centrally located.

5. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, a heater element within said envelope, a hollow anode surrounding said heater element but spaced therefrom and within said envelope, 2. control electrode surrounding said heater element and spaced intermediate said anode and said heater element, an apertured cathode surrounding said heater element and spaced intermediate said control electrode and said heater element, said apertured cathode having a coating of electron emissive material thereon, and a hollow electrode for affecting charged particles of said medium spaced around said heater element and intermediate said heater element and said apertured cathode.

6. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, a heater element within said envelope, a hollow tubular shaped anode coaxially spaced around said heater element, a hollow tubular shaped control electrode coaxially spaced around said heater element and intermediate said heater element and said anode, a hollow tubular shaped apertured cathode coaxially spaced around said heater element and intermediate said control electrode and said heater element, said apertured cathode having a coating of electron emissive material thereon, a hollow tubular shaped electrode for afiecting charged particles of said medium coaxially spaced around said heater element and intermediate said heater element and said perforated cathode.

7. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, a hollow tubular shaped auxiliary anode surrounding a heater element and within said envelope, a hollow tubular shaped main anode coaxially spaced around said auxiliary anode, a control electil trade coaxially spaced around said auxiliary anode and intermediate said auxiliary anode and said main anode, a hollow tubular shaped perforated cathode coaxially spaced around said auxiliary anode and intermediate said auxiliary anode and said control electrode, and said perforated cathode having a coating 0t electron emissive material on both sides.

8. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, a hollow tubular shaped indirectly heated auxiliary thermionic cathode surrounding a heater element and within said envelope, a hollow tubular shaped anode coaxially spaced around said auxiliary cathode, a tubular shaped control electrode spaced coaxially around said auxiliary cathode and intermediate said auxiliary cathode and said anode, an apertured main cathode coaxially spaced around said auxiliary cathode and intermediate said auxiliary cathode and said control electrode, and said main cathode having a coating of elec tron emissive material on the side adjacent said control electrode.

9. A gas discharge device comprising, a sealed envelope having an ionizable medium therein, a heater element, an array of electrodes including an auxiliary anode, an apertured indirectly heated thermionic cathode, a control electrode and a main anode spaced in that order from said heater element and within said envelope.

10. A gas discharge device comprising, a sealed envelope having an ionizable medium therein, a heater element, an array of electrodes concentrically spaced around said heater element and including an auxiliary anode, an apertured indirectly heated thermionic cathode having an electron emissive coating thereon, a control electrode and a main anode spaced in that order around said heater element and within said envelope.

References Cited in the file of this patent UNITED STATES PATENTS