US2747121A - Gaseous conduction device - Google Patents

Description

May 22, 1956 M. N. SILVER 2,747,121

GASEOUS CONDUCTION DEVICE Filed July 23, 1953 2 Sheets-Sheet 1 FIG. I

INVENTOR. MODULATED OSGlLLATOR MARVN SLVER ATTORNEY M. N. SILVER 2 Sheets-Sheet 2 AMPLIFIER MARVIN N. SILVER INVENTOR Wm ATTORNEY May 22, 1956 GASEOUS CONDUCTION DEVICE Filed July 23, 1953 FIG. 5

/FIG. 6

GASEOUS CGNDUCT ION DEVICE Marvin N. Silver, New York, N. Y., assignor, by mesne assignments, to Gera Corporation, New York, N. r., a corporation of New Jersey Application July 23, 1953, Serial No. 369,799

3 Claims. (Cl. Pulls- 54) This invention relates to gaseous conduction devices which include two or more triodes and which may be used as amplifiers, limiters, modulated oscillators, or

emodulators. It has particular reference to gas filled devices which contain a quantity of radioactive material which causes constant ionization within an envelope. A restricted space between electrodes is supplied with ions and electrons and current is thereby permitted to flow between an anode and a cathode under the application of applied potentials.

Radioactivity within a gaseous discharge device has been used to produce constant ionization and constant current operation under certain conditions. Such devices have been employed as circuit components having the characteristics of very high resistors. They have been described in patent applications by W. L. Meier, filed November 22, 1952, Serial Number 321,999, and

by M. H. Shamos, filed November 22, 1952, Serial Number 322,020, now abandoned. Other disclosures which described similar devices having three or more electrodes include applications by W. L. Meier, Serial Numbers 354,218 and 354,219, filed May 11, 1953. When constant ionization is provided throughout the entire tube envelope the impedance between a cathode and a control electrode is relatively low and if these electrodes are used as the input circuit of an amplifier the high input current results in a high input power and low amplification.

The present invention restricts the ionization to a small space between two control electrodes out of range of the cathode and the electric field between the cathode and anode separates the positive ions and the negative electrons, drawing them through the control electrodes to the anode and the cathode respectively. Because the ionization is restricted to a region which does not include the control electrodes, the current to these electrodes is small and the input impedance to an amplifier circuit can be made quite high.

Ionization of the gas molecules is caused only by the radiation from the radium or other radioactive material within the envelope. The pressure in the envelope is high enough to prevent ionization by collision with ionized particles and the potentials used are low enough so that electron field emission and corona discharge cannot occur.

One of the objects to this invention is to provide an improved gaseous discharge device which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the invention is to provide a gaseous discharge device'which does not require a heated cathode.

Another object of the invention is to provide a gaseous discharge device which can be operated at low voltages and low current and can therefore be used to transmit small amounts of power.

Another object of the invention is to separate the negative electrons and the positive ions formed by radionited States Patent 6 2,747,121 Patented May 22, 1956 ice active radiation and to use these electrons and ions for the passage of current.

The invention comprises a gaseous discharge device which comprises an envelope filled with an ionizable gas. A cathode and an anode are positioned within the envelope on either side of a source of ionizing radiation such as radium which is arranged to ionize a restricted region between the two electrodes. A first control elec-' trode is positioned between the anode and the restricted ionized region while a second control electrode is posi-- tioned between the cathode and the ionized region. EX- ternal sources of potential are applied to the electrode to cause control conduction within the envelope.

For a better understanding of the present invention together with other and further objects, thereof, reference is made to the following description taken in connection with the accompanying drawings.

Fig. l is a cross sectional view of the discharge device.

Fig. 2 is a cross sectional view of the tube shown in Fig. 1 taken along line 2-2 of that figure.

Fig. 3 is a schematic diagram of connections indicating one of the methods of connecting the tube shown in Fig. l to act as an amplifier.

Fig. 4 is a schematic diagram of connections indicating the method of connecting the tube as a modulated oscillator.

Fig. 5 is a diagram of connections showing an alternate method of connecting the tube to act as an amplifier.

Fig. 6 is a diagram of connections showing how the conduction tube may be connected as a switch, actuated by positive and negative input pulses.

Referring now to Figs. 1 and 2 an envelope 10 which may be of glass contains five electrodes and a quantity of radioactive material. A flat plate 11 which may be either an anode or a cathode is mounted near the envelope wall. A similar plate 12 which also may be used either as an anode or a cathode is mounted in opposite relation to plate 11. Two channels 13 and 14 are mounted within the tube with their open ends facing each other and substantially mid-way between the two plates 11 and 12. Radioactive material 15 and 16 is deposited within the channel electrodes 13 and 14 in such manner as to restrict the alpha particles and other ionizing radiation to a central portion of the tube. Two control electrodes 17 and 18 are mounted so as to be inter mediate between the flat plates and the central region which is to be ionized. The two plates 11 and 12 have separate lead-in conductors which are sealed in the usual type of vacuum seal 20 for external connection. The two control electrodes 17 and 18 also are provided with separate lead-in conductors but the channels 15 and 16 are connected together and need only one leadin conductor.

It has been found by experiment that a very satisfactory pressure for such a tube is about one atmosphere, but the pressure is not critical and pressures ranging from 500 mm. to 5 atmospheres have been successfully employed. The best source of ionizing radiation is radium and when this material is used it is common practice to embed the material under a very thin coating of gold. This permits the ionizing radiation to pass through the film but prevents Radon from escaping into the gas. It is well known that alpha particles produce far more ionization than either the beta or gamma rays, therefore, any substance which is a good alpha emitter is satisfactory for this type of discharge device. However, experiment has shown that radioactive cobalt (27) which emits only beta rays may be employed for this type of gaseous discharge device.

The operation of this device as an amplifier is illustrated by a diagram of connections shown in Fig. 3. ,One

I trode a cathode.

of the plates is connected through an output winding 22 to the positive terminal of a source of potential 23 thereby making the electrode an anode. The other plate is connected through a similar output winding 24 to a negative source of potential 25 thereby making this elec- The negative terminal of the source of potential 23 and the positive terminal of the source of potential 25 are connected together and also connected to the two channels 13 and 14 which contain the radioactive material. The control electrode, which is positioned adjacent to the anode, is connected through an input winding 26 to the negative terminal of a biasing source of potential 27. The control electrode which is adjacent to the cathode is connected through a second input winding 30 to the positive terminal of a second biasing source of potential 31. An input winding 32 is coupled to input windings 26 and 30 and serves as a common input circuit component to deliver an electric voltage to both control electrodes. Another winding 33 is coupled to windings 22 and 24 and produces a single output voltage on a pair of output terminals.

When the sources of potential 23 and 25 are connected to the discharge device the electrons from the central ionized region are drawn to the anode while the positive ions formed at the same region are drawn toward the cathode. These two streams of charged particles pro duce the average current through windings 22 and 24. Now let it be assumed that an alternating electric wave is applied to winding 32 and produces at one interval of time a negative potential on the control electrode connected to winding 26 and a positive potential on the control electrode connected to winding 30. This condition causes a decrease in the average current through coils 22 and 24. When reverse potentials are applied at a second time interval to the two control electrodes the current through windings 22 and 24 will be increased.

- This provides output power in winding 33 which is available to a load circuit.

The diagram of connections shown in Fig. 4 generates sustained oscillations, the intensity of which are controlled by an input circuit having terminals 35, 36. The frequency of oscillation is determined by an inductive winding 37 and a capacitor 38. A source of potential 40 is connected between the electrodes 13, 14 which contain the radioactive material and one of the plates 11. Feedback potential is provided by coupling a winding 41 to winding 37, winding 41 being connected between conthereby changing the intensity of the anode-cathode current and-varying the amplitude of the generated oscillations. A voltage which is proportional to the modulated oscillations may be derived from several parts of i this circuit but it has been found desirable to connect the output terminals 42, 43 to the junction of the sources of potential which supply the two plate electrodes 11 and 12 and the electrode side of a resistor 44 which is in series with the source of potential 45.

The circuit shown in Fig. is an alternate form of amplifier circuit and is designed to be used when the input and output voltages and currents are small. Input terminals 50, 51 are connected across an input resistor 52 which is grounded at its mid'point. Blocking capacitors 53, 54 isolate the two control electrodes 17 and 13 and permit a direct current bias to be applied to each by bias batteries 55 and 56. The anode-cathode current is maintained by anode battery 57 in series with a resistor 58. Output terminals 60, 61 are connected to ground and to the anode 11 in series with a blocking capacitor 62. The operation of this circuit is substantially the same as a push pull amplifier stage with minor modifications as explained above.

The circuit shown in Fig. 6 can be made to block itself in either one of two conditions, no anode current, or maximum anode current. The input terminals 64, 65 are connected to the cathode 12 and one of the control electrodes 18 through a blocking capacitor 66. Electrode 18 is biased to a positive potential by battery 67. A second control electrode 17 is biased to a negative potential with respect to ground by battery 68. The anodecathode current is generally maintained by an anode source of potential in series with a resistor 71. Output terminals 72, 73 are indicated as connected across resistor 71 but the output voltage may be derived from other points in the circuit.

In order to explain the operation of this circuit, let it first be assumed that no current is flowing through the tube and that bias batteries 67 and 68 are of a sufficient value to keep the tube cut off. If now a negative pulse is applied to terminal 64 the potential of control electrode 18 is made more negative and conduction is started in the tube by permitting the ions to migrate from the central ionized region. The current through the tube provides a voltage drop across resistor 77 (which in the non-conducting condition has been zero) and the upper end of the resistor is made more positive than the lower end. This action inserts a potential in series with bias battery 63 and partly counteracts its effect, making the potential of control electrode 17 less negative and permitting more anode-cathode current to flow. The action continues until the maximum current is flowing through the tube or until a limiting circuit establishes a stable condition. Such a circuit is shown connected between battery 68 and ground and comprises a bias battery 75 and a rectifier 76. No current flows in this circuit as long as the voltage across its terminals is less than the voltage of battery 75, but when this voltage is exceeded a current flows through the rectifier, the battery 75, and cathode resistor 77, limiting the voltage to that value.

When it is desired to cut off the current through the tube, a positive pulse is applied to terminal 64 and the current through the tube is thereby reduced. This reduction causes a reduction of the voltage drop across resistor 77 and further reduces the current by providing a greater negative potential for control electrode 17. The action is cumulative and the anode current is immediately reduced to zero, at which value it remains until a negative pulse is again applied to terminal 64.

Since there is a constant source of ionization within the tube, both positive ions and negative electrons will be present within the gas at all times and for this reason current flow between electrodes 11 and 12 may be reversed.

From the above description it will be evident that the tube has most of the characteristics of a double triode vacuum discharge device with a heated cathode, and that it can be used as a mixer as well as an amplifier and oscillator. It should also be evident that similar dis charge devices can be constructed with multiple grids. While there have been described and illustrated specific embodiments of the invention, it will be obvious that various changes and modifications can be made therein without departing from the field of the invention which. should be limited only by the scope of the appended claims.

I claim:

1. A gaseous conduction device having at least four electrodes comprising, an envelope filled with an ionizable gas, a cathode and an anode within said envelope, a source of ionizing radiation positioned between two control electrodes for ionizing the gas, a first control electrode positioned adjacent to the anode, a second control electrode positioned adjacent to the cathode, and barrier means partly enclosing the source of radiation for restricting the ion- 5 izing action to a region between the first and second control electrodes.

2. A gaseous conduction device having at least four electrodes comprising, an envelope filled with an ionizable gas, a cathode and an anode within the envelope, a source of ionizing radiation positioned between two control electrodes for ionizing the gas, a first control electrode positioned adjacent to the anode, a second control electrode positioned adjacent to the cathode, and a metallic support for said source of ionizing radiation which restricts the ionizing action to a region which lies between the first and second control electrodes, said region spaced apart from the control electrodes.

3. A gaseuos conduction device having at least four electrodes comprising, an envelope filled with an ionizable gas, a cathode and an anode within the envelope, a source of ionizing radiation positioned between the cathode and the anode for ionizing the gas, a first control electrode positioned adjacent to the anode, a second control electrode positioned adjacent to the cathode, and a metal channel open at one side for supporting said source of ionizing radiation and for restricting the ionizing action to a region which lies between the first and second control electrodes, said region spaced apart from the control electrodes.

References Cited in the file of this patent UNITED STATES PATENTS 1,145,735 Ainsworth July 6, 1915 1,269,534 Gray June 11, 1918 2,304,412 Kern et a1. Dec. 8, 1942 2,616,986 Coleman Nov. 4, 1952

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