US2578571A - Electron discharge device - Google Patents

Description

Dec. 11, 1951 w. L. MEIER ELECTRON DISCHARGE DEVICE 2 SHEETSSHEET 1 Filed March 21, 1951 all INVENTOR. WILBER L. MEIER ATTORNEY Dec. 11, 1951 w. 1.. MEIER ELECTRON DISCHARGE DEVICE 2 SHEETS-SHEET 2 Filed March 21, 1951 FIG.8

FIG.7

N H w u mag INVENTOR. WI LBER L. MEIER BY w- ATTORNEY Patented Dec. 11, 1951 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to electron discharge devices, and has particular reference to improvements in such devices having a gaseous atmosphere and capable of being continuously controlled over a wide range of anode supply potentials.

In the conventional gas-filled tube having a cathode, an anode, and a control electrode, ionization of the gas and the creation of a plasma causes the control electrode to lose its control of the electron stream so that while initiation of ionization can be controlled, the current cannot be controlled by the control electrode after ionization takes place. Also the conventional gasfilled tubes employ anode voltages which are many times the gas ionization voltage, a fact which limits its use considerably.

An attempt has been made to design a gasfilled discharge device, the anode current of which can be controlled by a small amount of input power. Patent No. 2,130,191, issued September 13, 1938, and Patent No. 2,158,564, issued May 16, 1939, disclose a discharge device comprising a main cathode and a main anode. An auxiliary cathode-grid-anode combination positioned outside the main cylindrical anode furnishes the flow of electrons which controls the main anode-cathode current. The disadvantage of this system is due to the fact that the main anode voltage cannot exceed the ionization potential of the gas used. A six volt anode battery is suggested for this type of tube. The present invention comprises a discharge tube having a controllable anode-cathode current and at the same time using an anode voltage which may be many times the ionization voltage of the gas.

One of the objects of this invention is to provide an improved gas-filled electron 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 gas-filled discharge device which permits the flow of several amperes between the anode and cathode while subject to the control of a circuit which consumes a small amount of power.

Another object of the invention is to provide a discharge device which permits an extremely high mutual conductance.

Another object of the invention is to generate high voltage alternating current by the use of an oscillating circuit and tube using a comparatively low anode voltage.

One feature of the invention comprises an auxiliary cathode-grid-anode system, arranged thereof, reference is made to the following description taken in connection with the accompanying drawings.

Fig. 1 is a cross sectional view, partly schematic, of an electron discharge device.

Fig. 2 is a cross sectional view, taken along lines 22 of Fig. 1. I

Fig. 3 is a schematic diagram of connections showing how the discharge device may be connected as an amplifier with modulation voltages applied to the main control electrode.

Fig. 4 is a schematic diagram of connections of an alternate type of tube having an additional grid and used as an oscillator.

Fig. 5 is a cross sectional view, partly schematic, of a, discharge device similar to that shown in Fig. 1, but employing a different arrangement of parts. I

Fig. 6 is a cross sectional view of the tube shown in Fig. 5 taken along line 6-6 of that figure.

Fig. 7 is a schematic diagram of connections showing the tube connected as an amplifier with modulation voltages applied to the auxiliary control electrode.

Fig. 8 is another schematic diagram of connections showing the tube connected as an amplifier and modulation voltages applied to both control electrodes.

Referring now to Figs. 1 and 2, the discharge device is' contained in a glass envelope l0, and is mounted in a conventional manner on a reentrant stem 1 l which also serves to seal a number of the electrode leads. The envelope contains gas at a reduced pressure. A main anode I2 consists of a cylindrical conductor partially closed at the top and bottom ends. A main control electrode I3 is mounted inside the anode and in close proximity to its inside surface. This control electrode may be made of a wire mesh or a system of parallel wires mounted on conventional supporting means. The spacing between electrode I3 and the anode I2 is considerably less than the mean free path of electrons in the gas so there will be no glow discharge between these two electrodes. Connection of the main control electrode is made by means of a conductor M which is brought out through the glass envelope H1 near the top of the tube. A main cathode I5 is positioned at the center of the anode and may be either the filament or heater type. Fig. 1 indicates the usual heater type of cathode having a cylindrical tube l6 and heater wires II. In order to securely anchor the cath ode. a bead I8 is formed near the upper end and two insulating washers 20 are secured to the anode, clamping the bead i8 between them, thereby holding the cathode in place. A cathode lead 2| is brought out through the envelope near the top of the tube, as are also the heater leads I].

At the bottom portion of the anode, a hole 22 is provided to permit high speed electrons to enter the discharge chamber. These electrons are formed by an auxiliary triode which comprises a heater cathode 23, a control electrode 24, and a perforated anode 25. The anode 25 may be made of mesh or a series of parallel, closely spaced wires. While there are some applications where the anode 25 is connected directly to anode l2, the two anodes usually must be separate and have their own source of potential. For this reason separate leads are brought out through the seal I I. In the description that follows, these three electrodes 23, 24, 25, will be termed the auxiliary cathode," auxiliary grid," and "auxiliary anode. The spacing between these electrodes is made considerably less than the mean free path of the electrons in the gas so that the auxiliary electrodes function in the same manner as the electrodes in a triode in a high vacuum envelope.

When the tube described above is operated, the voltage between the main anode I5 and the main control electrode I3 is always less than the ionization potential of the gas used and, therefore, there is no glow discharge started or maintained by this potential field alone. The voltage difference between the control electrode l3 and the anode l2, however, may be several times the ionization potential.

The auxiliary electrodes 23, 24, and 25, positioned in Figs. 1 and 2 outside the main anode space, are used to generate fast moving electrons which are projected through the perforated auxiliary anode 25 and ionize the region adjacent to the main cathode IS. The ionization may be of a steady continuous nature or may be modulated by a varying potential applied to the auxiliary control electrode 24. In either case the amount of ionization caused by the auxiliary electrodes determines the amount of current that may flow from the main cathode toward the anode. If the main control electrode I3 is held at a steady potential which is approximately equal to the potential of the cathode, the modulations of the main anode current are controlled by the potentials applied to the auxiliary control electrode 24. If a steady stream of fast moving electrons is projected into the cathode-anode space, the potentials applied to the main control electrode l3 determine the main anode current. It will be obvious that various combinations involving separate potentials applied to the two control electrodes may be used to control the anode current.

The diagram of connections in Fig. 3 illustrates one method of wiring the tube for use as an amplifier. An input transformer 25 is arranged with its secondary winding 21 connected between the main control electrode l3 and ground. The main anode I2 is connected to the primary Coil 28 of an output transformer 30 and an anode battery 3|. The auxiliary electrodes 23, 24, and 25, project a stream of high speed electrons into the anode-cathode space and cause a supply of electrons and positive ions to be available at all times between the central cathode I5 and the control electrode l3. A battery 32 or other source of potential is connected between auxiliary perforated anode 25 and ground, and a bias battery 33 is connected between control electrode 24 and ground. This latter battery may be made variable to function as a manual volume control. When the control electrode I3 is varied in potential it maintains control of the main anode current because no ion sheath can be formed between the two electrodes.

The diagram of connections shown in Fig. 7 illustrates another method of wiring the tube for use as an amplifier. In this illustration the main control electrode [3 is directly connected to'the main cathode l5 and for this reason there can be no electric field surrounding the main cathode space. An intense electric field exists between the main control electrode I3 and the main anode l2, hence all available electrons near the control electrode perforations are drawn to the anode l2. Under these conditions the amount of anode cur-. rent is proportional to the ionization of the gas in the main cathode space. This ionization can be caused only by the projected elec rons from the auxiliary electrodes and the intensity of this ionization is controlled by the potential of auxiliary control electrode 24 which is connected to the secondary winding 21 of input transformer 26. It should be evident that the potential of the main anode l2 may be many times the value of the ionization potential of the gas since the entire field is confined between electrodes I2 and I3, the spacing of which is too small to permit ionization to start unaided by some outside source.

The diagram of connections shown in Fig. 8 is a combination of the two circuits described above. An input transformer 35 is employed having two secondary windings 35 and 31. Winding 36 is connected between the main cathode l5 and the main control electrode I3. Winding 31 is connected between the auxiliary control electrode 24 and the auxiliary cathode 23. Windings 36 and 31 are connected so that both control electrodes are varied in potential in the same polarity. Bias batteries 33 and 38 are added to reduce the flow of current to the two control electrodes. The result of this method of operation is an amplifier of high sensitivity having a high input impedance and low output impedance.

Figs. 5 and 6 illustrate an alternate arrangement of the electrodes shown in Figs. 1 and 2. In this design the auxiliary cathode 40 is mounted in the center of the tube (envelope not shown) and the auxiliary control electrode 4| and auxiliary perforated anode 42 are mounted in concentric alignment as shown in Fig. 6. The main cathode is composed of a plurality of small cylindrical heater cathodes 43 (six shown in Fig. 6). These are all connected to a single terminal and function in the same manner as the single main cathode 15 shown in Figs, 1 and 2. The main anode I2 and the main control electrode l3 are similar to the corresponding electrodes shown in Figs. 1 and 2. The operation is the same as that already described except that the auxiliary electrodes project the high speed electrons through the perforated anode 42 past the cathodes 43 and directly toward the main electrode I3.

Fig, 4 illustrates the use of the tube (with an additional electrode 48) connected as anoscillator for class C operation. For this application the auxiliary electrode structure need project electrons into the main discharge space only a small part of each cycle. To accomplish this the control electrode 24 is coupled to the main anode H by two windings 46, 41 of a transformer. Coupling the auxiliary cathode 23 and the main control electrode I: by similar coils 48, 50 makes the action more positive and reliable. However, even with these couplings the circuit does not start each time the power is connected because a positive voltage pulse on electrode 24 is needed to project the first beam of electrons into the main discharge space and cause a negative current pulse in the main anode conductor. To supply the initial pulse a relaxation oscillator circuit is coupled tothe additional electrode 45 and capacitor 52 which is connected across ground and the positive battery terminal.

While there have been described and illustrated specific embodiments of the invention, it will be obvious that various changes and modifications may 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. An electron discharge device comprising, an envelope containing a gas, a main thermionic cathode within said envelope for emitting electrons, a hollow main anode surrounding the thermionic cathode for enclosing the space between the main cathode and main anode, a main control electrode mounted adjacent to the inside surface of the main anode, and means for ionizing the space between the main cathode and the main control electrode, said means including an auxiliary cathode and an auxiliary perforated electrode through which electrons from the auxiliary cathode can pass into the space between the main cathode and the main control electrode.

2. An electron discharge device comprising, an envelope containing a gas, a main thermionic cathode within said envelope for emitting electrons, a hollow main anode surrounding the thermionic cathode for enclosing the space between the main cathode and main anode, a main control electrode mounted adjacent to the inside surface of the main anode, means for ionizing the space between the main cathode and the main control electrode, said means including an auxiliary cathode and an auxiliary perforated electrode through which electrons from the auxiliary cathode can pass into the space between the main cathode and the main control electrode, and means for applying a voltage between the auxiliary cathode and the auxiliary perforated electrode for causing electrons to be projected into the space between the main cathode and the main control electrode with suflicient energy to ionize the gas therein.

'3. An electron discharge device comprising, an envelope containing a gas. a main thermionic cathode within the envelope, a hollow main anode surrounding the thermionic cathode for enclosing the space between the main cathode and the main anode, a main control electrode mounted adjacent to the inside surface of the main anode spaced therefrom a distance which is small in comparison to the mean free path of electrons in the gas, and means for ionizing the space between the main cathode and the main control electrode, said means including an auxiliary cathode and an auxiliary perforated anode through which electrons from the auxiliary cathode can 6 pass into the space between the main cathode and the main control electrode.

4. An electron discharge device comprising, an envelope containing a gas, a main thermionic cathode within the envelope. a hollow main anode surrounding the thermionic cathode for enclosing the space between the main cathode and the main anode, a main control electrode mounted adjacent to the inside surface of the main anode spaced therefrom a distance which is small in comparison to the mean free path of electrons in the gas, and means for ionizing the space between the main cathode and the main control electrode, said means including an auxiliary cathode, an auxiliary control electrode, and an auxiliary perforated anode through which controlled electrons from the auxiliary cathode can pass into the space between the main cathode and the main control electrode.

5. An electron discharge device comprising, an envelope containing a gas, a main thermionic cathode within the envelope, a hollow main anode surrounding the thermionic cathode for enclosing the space between the main cathode and the main anode, a main control electrode mounted adjacent to the inside surface of the main anode spaced therefrom a distance which is substantially less than the mean free path of electrons in the gas, means for ionizing the space between the main cathode and the main control electrode: said means including an auxiliary cathode, an auxiliary control electrode, and an auxiliary perforated anode; and means for applying voltages to said auxiliary electrodes to cause high velocity electrons to pass into the space between the main cathode and the main control electrode with sufficient velocity to ionize the gas therein.

6. An electron discharge device comprising, an envelope containing a gas, a main thermionic cathode within the envelope, a hollow main anode surrounding the thermionic cathode for enclosing the space between the main cathode and the main anode, a main control electrode mounted adjacent to the inside surface of the main anode spaced therefrom a distance which is substantially less than the mean free path of electrons in the gas, means for ionizing the space between the main cathode and the main control electrode; said means including an auxiliary cathode, an auxiliary control electrode, and an auxiliary perforated anode; means for applying a voltage between the auxiliary cathode and the auxiliary perforated anode to cause electrons to pass from the auxiliary cathode through the perforations in the auxiliary anode into the space between the main cathode and the main control electrode with sufficient velocity to ionize the gas therein: and means for app ying a control voltage to the auxiliary control electrode for controlling the electrons from the auxiliary electrodes and the resulting gas ionization.

7. An e ectron discharge device comprising, an envelope containing a gas at low pressure, a main thermionic cathode within the envelope, a hollow main anode surrounding the thermionic cathode for enclosing the space between the main cathode and the main anode, the main anode having an aperture provided therein, a main control electrode mounted adjacent to the inside surface of the main anode spaced therefrom a distance which is substantially less than the mean free path of electrons in the gas and having an aperture aligned with the aperture in the main anode, means for ionizing the space between the main cathode and the main control 1 electrode; said means including an auxiliary cathode, an auxiliary control electrode, and an auxiliary perforated anode positioned in alignment with the apertures in the main anode and main control electrode; and means forapplying voltages to said auxiliary electrodes to cause high velocity electrons to pass through the perforations in the auxiliary anode and through the apertures in the main control electrode and the main anode with suflicient velocity to ionize the gas between the main cathode and the main control electrode.

8. An electron discharge device comprising, an envelope containing a gas at low pressure, a. main thermionic cathode within the envelope, a hollow main anode surrounding the thermionic cathode for enclosing the space between the main cathode and the main anode, the main anode having an aperture provided therein, a main control electrode mounted adjacent to the inside surface of the main anode spaced therefrom a distance which is substantially less than the mean free path of electrons in the gas and having an aperture aligned with the aperture in the main anode, means for ionizing the space between the main cathode and the main control electrode; said means including an auxiliary cathode, an auxiliary control electrode, and an auxiliary perforated anode positioned in alignment with the apertures in the main anode and main control electrode; means for applying voltages to said auxiliary electrodes to cause high velocity electrons to pass through the perforatlons in the auxiliary anode and through the apertures in the main control electrode and the main anode with sufficient velocity to ionize the gas between the main cathode and the main control electrode; and means for applying a control voltage to the main control electrode for controlling the passage of electrons from the main cathode to the main anode.

9. An electron discharge device comprising, an envelope containing gas at low pressure, a plurality of main thermionic cathodes within the envelope arranged in circular formation, a hollow main anode surrounding the main cathodes, a main control electrode mounted adjacent to the inside surface of the main anode spaced therefrom a distance which is substantially less than the mean free path of electrons in the gas, means for ionizing the space between the main oathodes and the main control electrode; said means comprising an auxiliary cathode, an auxiliary control electrode, and an auxiliary perforated anode; all of said auxiliary electrodes positioned within the circular formation of the main cathodesyand means for applying voltages to said auxiliary electrodes to cause high velocity electrons to pass through the perforations in the auxiliary anode and between the main cathodes with suflicient velocity to ionize the gas between the main cathodes and the main control electrode.

WILBER L. MEIER.

No references cited.

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