US2239749A - Electron beam tube - Google Patents

Description

April 29, 1941. A. A. VARELA ELECTRON BEAM TUBE Filed April 24, 1959 2 Sheets-Sheet l ARTHUR A. VARELA ATTORNEY April 29, 1941. VARELA 2,239,749

ELECTRON BEAM TUBE Filed April 24, 1939 2 Sheets-Sheet 2 20 iii :5

INVENTOR ARTHUR A. VARELA ATTORNEY Patented Apr. 29, 1941 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, .1928; 370 O. G. 757) 3 Claims.

This invention relates to vacuum tubes of the type wherein the electron stream from the cathode to the anode is concentrated into beams.

Among the several objects of my invention are:

To provide grid controlled electron tubes of great sensitivity and high efficiency at high frequencies;

To provide vacuum tubes wherein the space charge transit time is very short;

To provide electron beam tubes wherein the space charge is essentially constant;

To provide high frequency tubes of useful power and sensitivity.

In the drawings:

Fig. l is a schematic drawing of the arrangement of the electrode elements of an oscillatoramplifier tube embodying my invention, the evacuated envelope and other parts being omitted for the purpose of simplicity;

Fig. 2 shows the equipotential lines in a section of a tube constructed as depicted in Fig. 1;

Fig. 3 is a schematic illustration of the electrode elements in a detector tube embodying my present invention;

Fig. 4 shows a suitable circuit for utilizing the tube of Fig. 3;

Fig. 5 is a schematic showing of the electrode arrangement for a detector tube having a screen grid and additional deflection grids for increased stability and sensitivity;

Fig. 6 depicts a form of my invention useful as a detector tube wherein secondary emission elements are used. 7

As employed hereinafter, the term linear cathode or linear member is intended to in- Y clude both a wire and a narrow strip. In all the figures, the reference character E designates a suitable envelope.

It is well known that conventional tubes employing grid control of the electron flow have that are very useful in the ultra-high frequency radio field.

Referring to Fig. l, the cathode l is a straight wire which may be of thoriated tungsten and is heated to cause the emission of electrons therefrom. symmetrically arranged about the oathode, 1 are the linear grid elements 8, 8 and 9, 9 which may be either narrow metal strips mounted parallel to cathode l and with their widths lying along radial planes of a circle whereof cathode 1 is the center or straight wires parallel to the cathode. The grid members 8, 8 are connected together as are also the members 9, 9.

Disposed around the grid members are anode members I0, I0 and. II, II, each of which is transversely arcuate and subtends substantially a quadrant and thus the four anode members constitute approximately a cylinder around the cathode 1 and grid members 8, 8 and 9, 9. Linear suppressor elements l2 are disposed one between each two anode members to prevent transfer of secondary electrons from one anode member to the other. All the suppressor elements l2 are connected together and the anode members l0, l0 and H, II are respectively connected to each other in pairs. The grid members 8, 8 are connected, when in operation, to one side of a balanced or push-pull input or tuned grid circuit with negative D. C. bias being supplied through the radio frequency node point in the conventional manner. Anode members [0, [0 are connected to one side of a radio frequency output circuit and the anode members H, II are connected to the opposite side thereof with the output circuit usually tuned to the same frequency as the input circuit. Positive potential is maintained on the anodes through connection at the node point of the output circuit. Suppressor plates I 2 are connected to a somewhat lower positive potential than that applied to the anodes. When used as an oscillator the grid and plate circuits are suitably coupled together. Conventional external circuits are shown to illustrate the connections to the tube elements.

The operation of this form of my invention is illustrated in Fig, 2 showing substantially one quadrant. Here it is assumed, for purposes of illustration, that grid members 9 have a negative voltage of 5 volts and grid members 8 are at negative 4 volts, which is equivalent to a fixed bias of negative 4 /2 volts with an instantaneous radio frequency voltage of A volt applied. Also, the D. C. voltage applied to the anodes is assumed to be +100 and if the amplification in the tube is 10 times,'which may reasonably be, the instantaneous anode voltages are 95 and 105. It

is assumed that suppressor plates l2 are at +80 volts. The equipotential lines l3 then show the distribution of the electrostatic field and the path of the electron beam is indicated by dotted .line M, with the dot and dash line [5 giving the disposed around the cathode. The grid members.

l6, l6 and I1, I! are substantially parabolic in transverse cross section and, due to the potential field between the limbs of each grid member the path of the electron stream between each two grid members is confined to a narrow beam. Opposite the openings between each two grid members is a narrow anode plate I8, all of which v are connected together and asubstantially U-shaped suppressor element isdisposed-around each anode plate 18. Anode members 22 ar disposed between thesuppressors 20 to constitute parts of a cylinder whereof the anode plates l8 form parts. As in the previously described form of my invention, the like-numbered grid members are connected together but in Fig. 3 all the anode members are connected together.

Fig. 4 illustrates a circuit suitable for use with the tube structure shown in Fig. 3. The pairs of grid elements l6 and I! are connected to opposite sides of an input circuit which is here shown as a Lecher quarter-Wave frame 23. Anode members 22 are connected to a source of positive potential through a resistor and anode plates l8 are likewise connected to source 24 through resistor 25 while suppressors 20 are connected to a somewhat lower positive potential on the same source 24. Cathod 1 and grid members l6 and H are suitably biased by a source 21. The grid negative bias is so adjusted that in the absence of radio frequency excitation the currentto anode members 22 is very slight with the great majority of theelectrons going to anode plates I8;

When excitation is applied to thegrid members the electron beams swing backand forth on the radio frequency cycle and the average current to anode members 22 increases while the average current to "anode plates I8 decreases. Thus, a voltage which varies in accordance with the modulation of the input signal is developed across resistors 25 and 26 and may be introduced to an amplifier or a load circuit by means of coupling condensers 21.

In Fig. 5 four filament wires 28 in parallel symmetrical arrangement at the corners of a square are employed as thesource of electrons. Parallel to and radially aligned with each cathode element 28 is an interior grid member 29 and an outer grid element 30 with the grid elements29 on opposite sides of the cathode elements being connected to the'grid elements 30 at the other two corners of the square, and the two groups of inter-connected. grid elements respectively connected to opposite sides of the input circuit. It is thus evident that when two of th grid elements 29 are swung more negative the other two elements 29 will go more positive and consequently the .electron beam will be deflected.

Disposed around the elements of Fig. 5 heretofore described is a screen grid 3| that may be spiral in form or may be amesh in some cases. Anode members 32, 32 are connected together asare anode members 33, 33. The equipotential lines 34, show the form of the electrostatic field. This. form of myinventionmay be used as. an

amplifier but is equally well adapted for detection when supplied with anode elements similar to anode plates [8 of Fig. 3. As the grid voltages vary, the electrons are drawn from the alternate pairs of the filament wires and are deflected to the diagonally opposite anode plates. Instead of separate wires 28, the cathode may be in the form of a single element that is square in cross section. The intensity of the beams increases with deflection and the tube may therefore be openated as class AB or class B and reasonably high efliciencies as an oscillator may be obtained.

Fig. 6 shows a form of my invention wherein the cathode 35 is at the center of-a square defined by four separate grid elements 36, 36 and 31, 31 which are connected together in pairs as shown. Opposite and. parallel to each grid element is a focusing electrode 38 and the anode members 40 are disposed with their center lines in: substantially the same lateral plane as the center lines of focusing electrodes 38. Between each two anode members is disposed an anode plate 4| with a substantially C-shaped suppressor element 42' around each anode plate. The exterior surfaces of the suppressors 42 are treated to give high secondary electron emission and the curvature of the suppressors is such as to present a treated area to be impacted by electrons moving toward the anode elements, thereby giving off a large number of secondary electrons and increasing the output. Conventionalv external circuits are shown to illustrate the connections to the tube elements.

In Fig. 6 the connectionof the anode members is for detection as in Fig. 3. The electron beams are normally focused to impinge upon the anode plates H but when the'beams are deflected by voltage changes on the grid members, the beams are swung from one anode member 40 to the other. The focusing electrodes 38 may be wires instead of strips as shown and in either case they have impressed upon them a small fixed bias. The electrodes 33 focus the beams and at the same time allow the deflection grid'elements 36 and 31 to operate in a low intensity field to give high sensitivity. The suppressor elements 42 are previously given a positive bias on the order of volts while'an'ode elements 40 and 4| have impressed upon them a somewhat higher positive potential. The anode members 42 are connected to an output circuit through a suitable impedance to develop an output voltage.

The invention herein described and claimed may be used and/or manufactured by or for the Government of the United States of America for governmental purposes without the payment of any royal-ties thereon or therefor.

I claim:

1. A beam vacuum tube, comprising a linear cathode, four grid members substantially parabolic'in transverse cross section symmetrically disposed about and withtheir length parallel to said cathode, a plurality of anode plates spaced equidistantly from said cathode and each disposed parallel to said cathode opposite a space between two grid members, a radially inwardly opening U-shaped suppressor member disposed around each of said anode plates, and a transversely arcuate anode member disposed between each two of said anode plates, the grid members on opposite sides of said cathode being connected together, said anode plates .being connected together and said anode members being connected together, whereby when said grid members, said anode members and said anode plates are properly biased the electrons from said cathode are caused to travel in beams to said anode plates, and when a varying signal potential is applied to said pairs of grid members the said beams are caused to shift between said anode members on opposite sides of said anode plates.

2. A beam vacuum tube, comprising a linear cathode, four linear grid members symmetrically disposed about said cathode at the corners of a square, the oppositely disposed said grid members being connected together in pairs, a linear focusing electrode disposed adjacent each said grid member and radially alined therewith, four transversely arcuate anode members disposed around said focusing electrodes with the longitudinal center line of each said anode member in the same radial plane as a respective grid member, a narrow anode element between each two of the aforesaid anode members, and an inwardly opening substantially C-shaped suppressor member around each said narrow anode element, said narrow anode elements being connected together, said suppressor members being connected together, and said anode members being connected together, whereby when the said members and elements are respectively properly biased the electrons from said cathode are caused to travel in beams, and varying signal voltages applied to said groups of grid members cause said beams to shift from a narrow anode element to an adjacent ber, a narrow anode element between each two of the aforesaid anode members, and means disposed between each said anode element and the adjacent anode member having a surface emissive of secondary electrons when impacted by electrons from said cathode, said anode elements being connected together, said means being connected together and said anode members being connected together, whereby when said members and said elements are properly biased the electrons from said cathode are caused to travel in beams, and varying voltages applied to said groups of grid members cause said beams to shift from a narrow anode element to an adjacent anode member and said means are impacted to yield secondary electrons.

ARTHUR A. VARELA.

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