US2292382A

US2292382A - Gaseous discharge tube system

Info

Publication number: US2292382A
Application number: US693294A
Authority: US
Inventors: James D Van Le
Original assignee: Raytheon Production Corp
Current assignee: Raytheon Production Corp
Priority date: 1933-10-12
Filing date: 1933-10-12
Publication date: 1942-08-11
Anticipated expiration: 1959-08-11

Description

Aug. 11, 1942.

J. D. L5 VAN GASEOUS DISCHARGE TUBE SYSTEM Original Filed Oct. 12', 1933 I ATTORNEY Patented Aug. 11, 1942 UNITED STATE GASEOUS DISCHARGE runs SYSTEM James D. Le Van, Belmont, Mass, assignor to Raytheon Production Corporation, Newton, Mass, a corporation of Delaware Application October 12, 1933, Serial No. 693,294 Renewed September 6, 1938 11 Claims.

This invention relates to systems utilizing gaseou s discharge tubes of the type in which an ionizing gaseous discharge serves as a source of current carriers for a controlled space discharge.

One of the objects of the invention is to provide a simple and effective means for controlling the mutual conductance of such a tube.

Another of the objects of this invention is to provide a particularly simple and effective amplifying circuit for the discharge tube of the type described above.

The objects and novel features of the invention will bebest understood from the following description of exemplifications thereof, reference being had to the accompanying diagrammatic drawing, wherein:

Fig. 1 is a diagram illustrating one embodiment of my novel system and showing a tube in section which may be used therein:

Fig. 2 is a diagram of another embodiment of my invention; and

Fig. 3 is a curve showing one of the characteristics of the tube illustrated.

In Fig. 1 the gaseous discharge tube which I utilize consists of a gas-filled envelope I, preferably of glass, having a reentrant stem 2, the upper 'end of which carries a press 3 in which are sealed a number of lead-in electrode supporting wires. Above the press and within the envelope I are supported a number of electrodes. these electrodes consists of a cathode 4. This cathode is of the usual type of indirectly heated cathode ordinarily used in vacuum tubes, and consists of a hollow metal cylinder 5 coated on the exterior thereof with electron-emitting material 6, such as, for example, the oxides of alkali earth metals. The coating is heated to thermionic emission by means of an internal heater consisting usually of a coil of fine wire. The two ends of the heating filament 1' and 8 are connected to the two' wires 9' and I0 sealed in the press 3. Surrounding the cathode 4 is the socallo'd cathanode I. This cathanode consists of an ':extended electrode having perforations over its .surface, and preferably is in the form of a fine wire grid. Surrounding the cathanode 'I and substantially concentric therewith is the control element 8 which likewise consists of an electrode of substantial area having perforations over its surface and which is preferably in the form of a fine wire grid. Surrounding all of the other electrodes and substantially concentric therewith is the anode 9 which is preferably formed of a thin solid metal plate. The cathanode is preferably supported in position by means of supporting One of standards II and I2. Two metal-plates l3 and I4 close the upper and lower open ends of the cylindrical cathanode I. The plates I3 and I4 have an opening it in the center thereof through which the cathode 4 passes freely. The cathode 4 is supported from the two plates l3 and I4 by means of insulators I6 and H. The control electrode 8 is supported by supporting standards [8 and I9 while the anode 0 is supported from a supporting standard by havinga radial member 2| extending from said anode 9 and engaging said supporting standard 20. All of said electrodes are maintained in a definite relative position by the two

insulating plates

22 and 23, which have small openings whichreceive the upper andlower ends respectively of the various supporting standards. External connections to the heatporting standard 20 for the anode 9 also has its lower end sealed in the press 3, and an external conductor 30 connected thereto establishes an external connection for said anode. An additional supporting standard 3| whose lower end is sealed in the press 3 passes through openings in the upper and lower

insulating members

22 and 23, respectively, and serves. as an additional support for the electrode structure. The

lower end of the supporting standard IQ of the control electrode 8 is welded to the supporting standard 3|. An external conductor 32 connected thereto establishes an external connection to the control element 8. The envelope I is evacuated in accordance with the usual vacuum technique. After the tube has been evacuated, it is filled with a gas filling, such as helium The gas pressure of the fill.-

ever, this gas pressure is sufficiently high so that an ionizing discharge can be maintained between the cathode 4 and the cathanode l whichproduces suflicient positive ions to neutralize the space charge between said two electrodes. When a vapor is used, such as, for example, mercury vapor, a quantity of mercury 33 is introduced into the utbe.

The tube as described above operates substantially in accordance with the principles as set forth in my co-pending application, Serial. No. 477,495, filed August 25, 1930. By establishing a discharge between the cathode 4 and the cathanode I, the gas in the space between said two electrodes is ionized. A large number of the electrons which pass into the gaseous discharge space between the cathode and the cathanode and flow toward the cathanode I will pass through the screen openings in said cathanode, and once having gotten into the space outside of said cathanode, will come under the influence of the control electrode 8. The spacing between the anode 9 and the cathanode l is such that under the pressure conditions existing in the tube, the distance between the opposing electrode surfaces is of the order to magnitude ofthe mean free path of the molecules in the gas. Due to this spacing, a comparatively large voltage can be impressed across these electrodes without introducing independent ionizing discharges therebetween. With greater spacing, such voltages would produce independent ionizing discharges which are very difficult to control by such a control member as 8. With the shorter spacing, any dischar'ges'which occur between the anodes 8 and the cathanode l are directly the result of electrons which pass from the gaseous discharge space through the openings in the cathanode I. Under these conditions a complete control of this discharge can be secured by a potential on is laid off along .the horizontal axis; Gm represents the mutual conductance of the tube, and is laid off along the vertical axis. As the values of mutual conductance are plotted against the values of cathanode current, we obtain the curve C as shown in Fig. 3. From such a curve I have determined that the mutual conductance bears substantially the following relationship to the cathanode current:

. where K is a constant depending upon the pathe controlmember 8. It will be noticed that in the construction, as shown, there are various elements, such as the supporting standards connected to the anode, the cathanode and the control grid, between which paths of substantially greater length than the spacing between these various electrodes exist. If free electrons in considerable number .were allowed to escape from the gaseous discharge space between the -cath ode and the cathanode into these relatively long discharge spaces, independent and uncontrollable gaseous discharges might occur between the anode, the control electrode, and the cathanode. Such discharges would very likely destroy the control features of the control grid, and therefore it has been necessary to adopt some means for preventing such uncontrollable discharges from occurring. This has been done by preventing electrons or other current carriers generated in the discharge space between the cathanode and the cathode from escaping into said long discharge spaces. First of all, the upper and lower ends of the cathanode have been closed by the two plates l3 and I4, thereby preventing escape of electrons from the discharge space through the ends of the cathanode. After the electrons have passed from the cathanode, the spacing between the cathanode, the control grid, and the anode is so small that there is substantially no tendency for the electrons to escape mutual conductance of the tube and the cathanode current of certain tubes of the present type which I have tested is shown in Fig. 3, in which Ica represents the amount of current flowing between the cathode and the cathanode, and

rameters of the tube. While this condition exists in certain tubes which I have examined, it may be possible that the particular relationship between these qualities may differ with different types of construction. However, in each gaseous discharge tube of the general type which I have illustrated, there will be some such definite relationship between the mutual conductance of the tube and the cathanode current as I have indicated above.

In order to utilize the above feature of my invention, the tube illustrated may be connected in some such circuit as illustrated in Fig. 1. In this system the heating filament is furnished with heating current by connecting the wires 24 and 25 to some suitable source of heating current, such as the battery 34, the amount of current being determined by the resistance 35 in series with said battery. The signal to be I amplified is impressed upon the

terminals

36 and 31 of the primary 38 of a coupling transformer. The secondary 39 of said coupling transformer may have connected across its terminals a variable tuning condenser 40. One terminal of said secondary 39 is connected through the conductor 32 to the control electrode 8. The other end of said secondary 39 is connected through the biasing battery 4| to cathode conductor 28. In this manner the signal impressed across the

terminals

36 and 31 is in turn impressed between the cathode 4 and the control electrode 8, the biasing battery 4| giving to the control electrode 8 a negative bias. This bias may be of any convenient value. In typical embodiments of my invention I have used values of negative bias ranging from 0 to 5 volts. The potential for the maintaining of the ionizing discharge between the cathode 4 and the cathanode l is supplied by a battery 42, the positivepole of which is connected to the cathanode 1 through the conductor 29, and the negative pole of which is connected through a controlling device 43 to the conductor 28 leading to the oathode 4. The condition which the value of the potential supplied by the battery 42 must satisfy is that it must be sufiicient to impress between the cathode 4 and the cathanode l a potential sufficient in magnitude to sustain an ionizing discharge between said electrodes. In order to prevent the anode current from producing undesirable changes in cathanode current, I prefer to utilize a high value of potential for the battery 42 and connect in series therewith a device across which the passage of the current from the battery 412 will produce a comparatively high drop, preferably several times the potential appearing between the cathode 4 and the cathanode 7. If a high vacuum tube is utilized as the control device 43, such a tube will have a sufficiently high drop across it to take care of this effect. If, however, some other type of control device having an inherently low voltage drop is used, it may be necessary to connect an additional resistance in series therewith to produce the necessary total voltage drop external to the cathode-cathanode discharge path. In typical embodiments of my invention I have utilized values of potential of the battery 2 ranging from about 50 volts to 150 volts. A battery 44 has its negative pole connected to the cathode & through the cathode conductor 28, and has its positive pole connected to one end of the primary 45 of an output coupling transformer. The other end of said primary 45 is connected to the conductor 39 which in turn is connected to the anode 9. The voltage of this battery 44 should be sufiiciently high to impress between the cathode 4 and the anode 9 a potential substantially higher than that appearing between the cathode 4 and the cathanode T. The voltage between the cathode 4 and anode 9 in typical embodiments may be between 50 and 500 volts. Of course higher or lower voltages may be used with difierent types of tubes. The secondary 46 of the output coupling transformer may have connected across its terminals a tuning condenser 41. Said secondary 46 and condenser 41 may constitute portions of a detector stage it. This detector stage may take any conventional form which possesses as one of its features an automatic volume control output voltage. A great number of detector stages of this type are known in the art, and it is believed to be unnecessary to illustrate any particular form of said detector stage 48. The automatic volume control voltage may be taken off from the detector stage from the two terminals 59 and 50 to which are connected the conductors and 52, respectively. As is well known, in an automatic volume control device, the voltage appearing across this portion of the detector stage is one which varies in magnitude in accordance with the magnitude of the signal voltage impressed upon the detector stage. In the particular embodiment which I have shown, the control device 43 may take the form of a space discharge tube having a cathode 53 and an anode 54, between which the discharge is controlled by a control grid 55. The detector stage as is arranged in such a way that the terminal dd becomes increasingly negative with an increase in the magnitude of the signal voltage impressed upon the detector stage. The terminal as which is positive with respect to the terminal as is connected through the conductor 52 to the positive terminal of the battery d2 while the terminal as is connected through the conductor St to the control grid 55.

Upon connecting the device as shown and impressing a signal voltage across the

terminals

38 and 3?, the signal will be amplifia by the gaseous amplifier tube, and the amplified output thereof will be impressed upon the detector stage $8. With a very weak signal, the negative potential upon the control grid 55 will be very low, thus allowing a comparatively large amount of current to flow through the control device as,

. and between the cathode and the cathancde i.

From Fig. 3 we see that by allowing a compara tlvely large amount of current to how from the the amount of current flowing through said con-- trol device. Therefore, upon such an increase in impressed signal, the current flowing between the cathode and the cathanode will decrease. Such a decrease in cathanode current will produce a decrease in the mutual conductanc of the tube in accordance with the characteristic as shown in Fig. 3. Therefore, an increased signal impressed upon the device will be amplified by the gaseous amplifier tube to a lesser degree than a weaker signal. The various constants of the system can be so selected that the resultant effect is to produce a substantially constant out-- put from the detector stage 48 with a varying intensity of signal input at the

terminals

36 and 31. Thus the arrangement as shown produces a particularly simple and effective automatic volume control for the system disclosed.

Although in 1 I have illustrated variation in the mutual conductance of my gaseous amplifie'r tube by automatic means responsive to the intensity of a signal impressed upon the amplifier, yet there are a great number of other systems in which it may be desired to have the mutual conductance of the gaseous discharge tube vary in accordance with some other quantity. Thus in Fig. 2 I have illustrated an amplifier systemutilizing my gaseous discharge tube, in which I have indicated diagrammatically means to independently vary the current between the cathode and the cathanode in order to vary the mutual conductance of the amplifier tube. In Fig. 2 the same reference numerals are applied to elements corresponding to those disclosed in Fig. 1. However, instead of controlling theamount of current between the cathode 4 and the cathanode 1, due to the impressed voltage of the battery 42 by such a controlling device as shown in Fig. 1, I utilize any other convenient controlling device. such as an adjustable resistance 55 in series with the battery 42 in the cathodecathanode circuit. manually adjustable. or any other desired means of varying this resistance may be utilized. Thus,

for example, if it is desired to control the dethe cathanode and the control electrode, I have found that the device shown herein operates in a much more satisfactory manner if the signal to be amplified is impressed directly between the cathode 4 and the control electrode 8, as shown in Figs. 1 and 2.. Due to the fact that the current between the cathode and the cathanode flows through a circuit which issubstantiaily in dependent of the output flowing in th anode circuit. the amount of anode current has substantially no effect upon the cathode-cathanode current. Thus with any setting of the system shown. either in Fig. l or Fig. 2, in which a dellnite amount of cathanode current is permitted to how between the cathode and the cathanode This resistance 56 may be I GUYS.

of the controlling device, the mutual conductance of the tube will remain substantially constant even with large variations in anode current.

Of course it is to be understood that this invention is not "limited to the particular details or construction as described above, as many equivalents will suggest themselves to those skilled in the art. For example, instead of taking the automatic volume control voltage from a detector stage, this voltage may be taken from any other part of a system in which a voltage varying in accordance with the magnitude of the signal oc- Further, although I have shown my system associated with the particular kind of gaseous amplifier device, this system can be utilized of current carriers for a controlled discharge with any gaseous amplifier in which a gaseous V discharge is to be utilized as as'ource of current carriers for a discharge space controlled by some control element. Various other changes in my system will readily suggest themselves.

It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art. i

What is claimed is:

1. In a gaseous discharge tube system, a gaseous space discharge tube comprising a gas-filled envelope containing means for producing a gaseous discharge through a space within said envelope, said gaseous discharge serving as a source of current carriers for a controlled .dis-

charge space, control means for controlling the discharge through said controlled discharge space, and an output electrode to which the controlled space discharge passes, and means for automatically varying the amount of current in said gaseous discharge space for varying the mutual conductance of said. tube in response to a predetermined controlling factor.

2. In a gaseous discharge tube system, a gaseous space discharge tube comprising a-gas-filled envelope containing means for producing a gaseous discharge through a space within said envelope, said gaseous discharge serving as a source of current carriers for a controlled discharge space, control means for controlling the discharge through said controlled discharge space, and an output electrode to which the controlled electrode can pass into a controlled discharge space discharge passes, means for impressing a signal on said control means, and means responsive to the magnitude of said signal for automatically varying the amount or current in said gaseous discharge space for varying the mutual conductance of said tube in accordance with the magnitude of said signal.

.3. In a gaseous discharge tube system, a gaseous space discharge tube comprising a gas-filled envelope containing means for producing a gaseous discharge through a space within said envelope, said gaseous discharge serving as a source of current carriers for a controlled dis charge space, control means for controlling the discharge through said controlled discharge space, and an output electrode to which the controlled space discharge passes, a controlled space discharge tube associated with said means for producing said gaseous discharge for varying the amount of current in said gaseous discharge space for varying the mutual conductance of said tube. I

4. In a gaseous discharge tube system, a gaseous space discharge tube comprising a gas-filled envelope containing means for producing a gasespace, control means for controlling the discharge through said controlled discharge space, and an output electrode to which the controlled space discharge passes, a controlled space discharge tube associated with said means for producing said gaseous discharge for automatically varying the amount of current in said gaseous discharge space for varying the mutual conductance of said tube in accordance with a predetermined controlling factor.

5. In a gaseous discharge tube system, a gaseous space discharge tube comprising a gas-filled enevelope containing means for producing a gaseous discharge through a space within said envelope, said gaseous discharge serving as a source of current carriers for a controlled discharge space, control means for controlling the discharge through said controlled discharge space, and an output electrode to which the controlled space discharge passes, means for impressing a signal on said control means, a controlled space discharge tubeassociated with said means for producing said gaseous discharge for varying the amount of current in said gaseous discharge space for varying the mutual conductance of said tube, said last-named tube being controlled by a control element, means ior varying said control element in accordance with the magnitude of said signal, whereby said last-named tube automatically varies the mutual conductance or said tube in accordance with the magnitude of said signal.

6. In a gaseous discharge tube system, a gaseous space discharge tube comprising a gas-filled envelope containing a cathode and a cooperating electrode between-which a gaseous discharge is adapted to take place, said cooperating electrode having openings through which electrons from the space between said cathode and cooperating space, control means for controlling the discharge through said controlled discharge space, and an output electrode to which the controlled space discharge passes, and means for automatically varying the amount of current in said gaseous discharge space for varying the mutual conouctance of said tube in response to a predetermined controlling factor.

7. In a gaseous discharge tube system, a gaseous space discharge tube comprising a gas-filled envelope containing a cathode and a cooperating electrode between which a gaseous discharge is adapted to take place, said cooperating electrode having openings through which electrons from the space between said cathode and cooperating electrode can pass into a controlled discharge space, control means for controlling the discharge through said controlled discharge space, and an output electrode to which the controlled space discharge passes, said output electrode being spaced from said cooperating electrode a distance sufficiently short to prevent independent ionizing discharges between said output electrode and cooperating electrode under comparatively high potentials applied therebetween, means for preventing ions or electrons from the space in which said first-mentioned discharge takes place from passing into spaces through which comparatively long ionizing paths between said output electrode and cooperating electrode exist, and means for automatically varying the amount of current in said gaseous discharge space for varying the mutual conductance of said tube in accordance with a predetermined controlling factor.

8. In a gaseous discharge tube system, a gastrode through said cooperating electrode into a controlled discharge space, control means for controlling the discharge through said controlled discharge space, and an ouput electrode to which the controlled space discharge passes, a circuit for impressing a" positive potential on said output electrode with respect to said cathode, a circuit substantially independent of and unaffected by current flowing in said first-named circuit for impressing a potential between said cathode and said cooperating electrode, means in said second-named circuit for varying the amount of space current flowing between said cathode and said cooperating electrode for varying the mutual conductance of said tube, and an output device connected to said output electrode.

9. In a gaseous discharge tube system, a gaseous space discharge tube comprising a gasfilled envelope containing a cathode and a cooperating electrode between which a gaseous discharge is adapted to take place, said cooperating electrode being adapted to pass electrons from the space between said cathode and cooperating electrode through said cooperating electrode into a controlled discharge space, control means for controlling the discharge through said controlled discharge space, and an output electrode to which the controlled space discharge passes, a circuit for impressing a positive potential on said output electrode with respect to said cathode, a circuit substantially independent of said firstnamed circuit for impressing a potential between said cathode and said cooperating electrode, a relatively high impedance in series with said cathode and cooperating electrode in said second-named circuit, and an output device connected to said output electrode.

10. In a gaseous space discharge tube comprising a gas-filled envelope containing means for producing a gaseous discharge through a space within said envelope, said gaseous discharge serving as a source of current carriers for a controlled discharge space, control means for controlling the discharge through said controlled discharge space, and an output electrode to which the controlled space discharge passes, the method of varying the mutual conductance of said tube which consists in varying the amount of current in said gaseous discharge space.

11. In a gaseous discharge tube system, a gaseous space, discharge tube comprising a gasfilled envelope containing means for producing a gaseous discharge through a space within said envelope, said gaseous discharge serving as a source of current carriers for a controlled discharge space, control means for controlling the discharge through said controlled discharge.