US1920863A - Amplification of radiant energy - Google Patents

Description

Patented Aug. 1, 1933 AMPLIFICATION or RADIANT ENERGY Matthew S. Hopkins, Jr., Washington, D. C. Appelation october 7, 1932. seriaiNo. 636,732

11 Claims.

This invention relates to improvements in the method and apparatus of the amplification of electrical energy. This result is obtained by producing a narrow beam of electrons and successively decelerating, guiding, accelerating and causing said beam to impinge alternately on two diierent receivers which may be the faces of two independent output electrodes or the faces of another electrode having two faces capable of emit- 0 ting secondary electrons, where bombarded. These secondary electrons so emitted are attracted either to more secondary electron-emitting electrodes or alternately to one and then the other of a pair of final electrodes.

15 More particularly described, the method of ampliflcation consists in sending a narrow beam of electrons between two or more input plates which are charged electrostatically by the input. At a distance from these input plates there is a screen 0 or grid so placed and charged that it will protect the electrons in the vicinity of the input elec-I trodes from the accelerating influence of the more highly electropositive iield beyond the screen or grid. In addition a plane partition or other dividing means is placed behind the screen or grid normally in line with the electron beam in its neutral position with its plane perpendicular to the direction of the movement of the electron beam when the latter is deected by u changes of difference in potential of the input plates.

This partition terminatesA at its edgev toward the input plates. within an inverted V-shaped member which when bombarded by the electron beam will emit secondary electrons on one or another side of the member. These electrons in turn migrate to the more positively charged electrodes on each side of the said partition.

The secondary electrons at the positively charged electrodes may migrate and in turn generate further secondary electrons from another electrode beyond the one from which they are emitted. This further electrode is more positively charged than the preceding one. The ilnal electrode in the series, which is determined by the degree of amplification desired, delivers its current to one end of a resistanceor impedance, the other end being similarly connected to the iinal electrode of the opposite series. The resistance or impedance is tapped at the center for connection to a source of positive potential greater than that of the series of secondary electronemitting electrodes. The output or load circuit may be shunted between the ends of this resistance or impedance.

CII

The object of this invention is to make possible an electron valve in which any of the following characteristics which it may be desired to incorporate simultaneously may be incorporated simultaneously to practically any desired degree Without sacrificing long life, durability or high eiiiciency; large amplification factor; small active control current; ability to give high voltage output, high current output, or both; no output background current; any desired mutual conductance curve and aperiodicity. y

Other objects will be apparent in the following description.

In the drawing I have shown a system for periodic amplification of weak radio waves, and 7e to avoid unnecessary illustration I have shown a special shield which would find most use in audio amplifiers or power ampliiiers. This shield will be explained with the amplier in the following description.

The shell 6 is a long glass cylinder enlarged at one end, 7. At the small end 8, is a filament 9, held' at a positive potential with relation to concentrating cylinder 10 by potential source l2. Co-axially mounted in front of concentrating cylinder 10 is a cone-shaped accelerating shield 13 with its apex, which has a hole in it,

' pointing toward filament 9.

This accelerating shield is held at a positive potential with relation to filament 9 by potential 85 source 14. Co-axially mounted with the accelerating shield 13 and 4extending into the interior of the large end of the said accelerating shield is a concentrating tube 15. This concentrating tube is held at a negative potential with relation to shield 13 by connecting it near filament 9.

In front of concentrating tube 15 is a pair of control electrodes 2 and 2'. Electrodes 2 and 2 are shunted by inductance 5 and capacitance 6. 95 To avoid confusion the effect of inductance 5 and capacitance 6 will be .ignored until they are further mentioned. I

Electrode 2' is connected to antenna 3 and electrode 2 is connected to ground 4 through in- 100 ductance 1. In front of control electrodes 2 and 2 is a screen or grid 16, which is held at a potential similar to that of the concentrating cylinder 15 by conductively connecting it thereto. In place of the electrodes 2 and 2' I may use 105 the customary helices for deflecting the beam.

The enlarged end of the tube contains a press 17 which is in axial line with electrodes 2 andre, 2'. The press 17 serves as a point of entry for conductors 18, 19, 20 and 21 and also, together 110 with a plane metallic partition 22, which is symmetrically mounted in the same axial line, to divide theenlarged end 7, of the shell 6, into two similar compartments-- A metallic member 23, having an inverted V- shaped cross-section is so conductively mounted on the electrode 22 that its apex isparallel with the plane of metallic partition or electrode 22 and its,two arms point away from screen 16. Conductively mounted on the apex of the inverted V-shaped member 23, is a shield 24, having two V-shaped apertures with their apices pointing in line and almost meeting at the center of the shield.

Electrode 22 is held at a positive potential with relation to the screen or grid 16 by potential source 25. Electrodes 26 and 26 are symmetrically placed, one on each side of partition 22 and behind the inverted V-shaped member 23. Electrodes 26 and 26' are connected to conductor 19 and held at a relatively'high positive potential with respect to electrode 22 by potential source 27.

Electrodes 28 and 28' are connected to conductor 20 and held at a high electropositive potential with respect to electrodes 26 and 26 by potential source 29. Electrodes 30 and 30' are placed one on each side of partition 22 and behind electrodes 28 and 28'.

Electrodes 30 and 30 are connected to conductor 21 and held at a high electropositive potential with relation to electrodes 28 and 28' by potential source 31.

It is to be understood that the-above electrodes 23; 26; 26'; 28; 28'; 30 and 30 are to be coated with some form of an 'alkali earth metal.

Electrodes 32 and 32' are placed one on each side of the press 1'7, and at a good distance behind electrodes 30 and 30.'. Electrodes 32 and 32 are connected one to arm 33 and the other to arm 33' of center-tapped resistance 33; 33' respectively. Electrodes 32 and 32 are held at a high electropositive potential with respect to electrodes 30 and 30' by connecting the centertap 34 to potential source 35.

As a means for tuning the output I have shown condenser 36.

In the tube, electrons are emitted from lament 9 and concentrated by the repulsion of cylinder 10 and attracted by the accelerating shield 13. Of the electrons approaching shield 13 some strike it and others pass through the hole in it. Those which pass through the hole are decelerated and concentrated by tube 15 and pass be- 'tween the ccntrol plates 2 and 2'.

The electrons can be decelerated to any desired degree by increasing the negativity of concentrating tube 15.

Input plates 2 and 2 act as a condenser which, with inductance 1 forms a series-resonant circuit. When an alternating electromotive force of the same frequency as theresonant frequency of the series-resonant circuit is set up between the ground 4, and antenna 3, a current will flow through the said series-resonant circuit. This current will be limited chiefly by the resistance of inductance 1. This current will set up an E. M. F. between electrodes 2 and 2' whose magnitude will vary directly with the current and inversely with the eiective capacitance between electrodes 2 and 2'.

drawn by the resonant circuit from the antenna 3 will be limited, no matter how low the resistance of inductance' 1. Therefore a method for obtaining a radical potential step-up cannot be had by The current, which can be decreasing the resistance of the inductance 1 but by decreasing the effective capacitance between plates 2 and 2 and neutralizing the increased capacitive reactance by increasing the inductance 1, without increasing its resistance.

Since decreasing the size of or the distance between electrodes 2 and 2 would decrease thev sensitivity ofthe vtube their effective mutual capacitance may not be decreased in this manner.

To avoid a limiting condition at this point I have conceived a method which I believe to be new and novel for neutralizing the effective capacitance between input electrodes. This consists in shunting the input electrodes 2 and 2 with inductance 5. The smaller the resistance and inductance of inductance 5, the less will be the effective mutual capacitance between electrodes 2 and 2', but the resistance of inductance 5 will tend to increase the power loss and thus decrease the potential between electrodes 2 and 2. (It is here assumed that the inductance 5 has an inductance relatively high to its resistance.) By increasing inductance 1 and properly propor- 'tioning inductance 5 while keeping the effective resistance of the network low, practically any degree of potential step-up may be obtained for any given frequency. However, since it would be diflicult to build a very high grade inductance that is variable I choose to shunt a small variable condenser 6, across the input electrode as a means for varying the point of resonance.

As the electrons pass between electrodes 2 and 2 they will be attracted toward either electrode 2 or 2 at any given point between electrodes 2 and 2' according to the potential difference between the said plates at that particular point at that particular time. (It is here assumed that the distance between the control electrodes is much less than a wave length.)

From this rule it can be seen that the electron stream emerging from tube 15 will be deflected the most when the active length of the electrodes is equal to one half the product of the wave length of the E. M. F. being amplied and the distance travelled by an electron in the beam during one cycle of the E. M. F. divided by the difference between the wave length of the E. M. F.

and the distance travelled by an electron in the beam during one cycle of the E. M. F.

Thus it will be seen that if the velocity of the electrons were made equal to the velocity of the radio waves it would be possible to increase the length of the electrodes 2 and 2' almost indefinitely. It is, however, practically impossible to make the electrons travel as fast as the radio waves and there must, therefore, be a compromise between the length of the control electrode and the velocity of the electrons.

Since to have long electrodes would entail an increase in the bulk of the tube I choose to have comparatively short electrodes and a very low electron velocity. Using only one pair of control electrodes a limit would be reached to the angle to which the beam could be deflected for a given potential difference between control electrodes.

A method for overcoming -this limit will be mentioned later but is not employed in the tube in the diagram. y 4

The scr een or grid 16 prevents the highly electropositive eld of the electrodes in the enlarged end of the tube from accelerating the electrons while they are in the vicinity of electrodes 2 and 2. After the electrons have passed from between electrodes 2 and 2' they pass through grid 16 and are highly accelerated by the highly electroing it to emit secondary electrons.

positive eld of the shield 24. Those passing electrode 2 when and where it was positively charged will some strike shield 24 and others pass through it. The number passing through it will be determined by the size of the opening in the shield 24 at the point where the beam approaches it and therefore, the degree to which the electrons of the beam were attracted toward electrode 2.

Those striking the inverted V-shaped member 23 cause it to emit secondary electrons. These secondary electrons are in turn violently attracted by electrode 26 and strike it with sumcient force to cause it to emit secondary electrons. The secondary electrons emitted by electrode 26 in turn are violently attracted to electrode 28, thus caus- The electrons from electrode 28 are violently drawn against electrode 30, thus causing it to emit secondary electrons. These electrons from electrode 30 are attracted by electrode 32. However, since no more positive electrode is adjacentto electrode 32 any secondary electron emitted therefrom returns thereto. Therefore, an electron current will ow from electrode 32 into arm 33 of centertap inductance 33 33'.' When electrode 2 is most positive, electrons travelthrough the other aperture in shield 24 and strike the other side of the inverted V-shaped member causing ,it to emit `electrons which in' turn ultimately cause a cur rent to oW into arm 33' of center-tapped inductance 33; 33'.

The apertures in the shield 24 need not be exactly V-shaped but can be shaped in any desired way according to the desired mutual conductance curve or any lack of linearity in the secondary emission. If the distance between the apices of the apertures in this shield is properly which can be had between the last pair of secondary electron emitting electrodes and the final electrodes. Therefore, tubes of this type can be built for virtually any output voltage.

Since -any number of stages of secondary emission can be built into the tube the'current output with which a tube can be built is practically unlimited. Both current output and voltage output can be increased almost indefinitely regardless of `the input because one aids an increase of the other and because the sensitivity of the tube is independent of its output.

The sensitivity of the tube can be increased almost indefinitely because the velocity o f the electron beam can be decreased almost indefinitely. A limit need not be reached when the electrons are decelerated to such an extent that the differences in velocity due to the differences in the amount of thermal energy imparted to the electrons while leaving the lament because they can be sent through an aperture and then ltered for differences in velocities by spreading them into a spectrum With an electrostatic or electromagnetic field.

Changes in the quantity of electrons having given velocity as they leave the filament and therefore in the number which bombard the inverted V-shaped member 23 for a given potential difference between control electrodes 2 and 2' can be compensated by placing an appropriate resistance at the point marked by the X which is next to potential source 25; or if necessary, by replacing the potential source 25 with an appropriate network of resistances and potential sources. y A n y VThe tube may be made aperiodic as desired without sacrificing eiiciency because both ,the capacitance between input electrodes and that between joutput electrodes can be increased indenitely. By connecting an appropriate resistance with t'he input electrodes and shunting this series circuit with an equal resistance connected in series with an appropriate inductance `the power factor and equivalent resistance of the input circuit can be kept constant regardless of frequency. I

Since the lament emits only-a very small portion of the electrons in the tube it can be made small and operated `at an unusually low potential, thus increasing the life of the tube.

I do not wish to confine the scope of [my claims to apparatus of the exact form described, for I realize that such things are possible as the use, in place of the hard vacuum and lean beam, a soft vacuum and a dense beam and a lower `operating voltage, and the use of screens or grids in place of plates for control electrodes and the use of a photo-electric surface in place of a filament as an initial source of electrons.

1. The combination in an electronic valve, of an electron beam and a pair of control electrodes so located thata change in potential difference between said electrodes will sway the beam means toproduce from the beam an intermittent stream of electronsY and one or more other electrodes re- 'ceiving said intermittent stream of electrons and amplifying this stream in the form .of emitted secondary electrons.

` 2. The combination within an4 electronic .tube valve, of an electron-beam, a pair of control electrodes so placed that a potential diierence between said electrodes will sway the said electron beam, a partition or other separating means held at a negative bias with respect to the output circuit of the valve, at the end of the tube so placed that when the beam is swayed by either of said control means itwill pass from one side of said partition or separating means to the other and a,

pair of collecting electrodes positively charged with relation. to source of said electron beam, said electrodes being connected to opposite terminals of an output circuit, one of said collecting electrodes being placed on either side of said partition or separating means.

3. The combination within an electronic tube valve, of an electron beam, a pair of electrodes so placed that a change in potential difference of said electrodes willsway said electron beam, a partition or other separating means so placed at the end of the tube opposite the source of the said electron beam, such that -when said electron beam is swayed by said control means its point of impingement will pass from one side of said partil the said partition or other separating means and both of which' are held at a positive potential with relation to said partition and to all other electrodes in the tube.

4.A The combination within an electronic tube valve, of an electron beam, a pair of control electrodes so placed that a change of potential difference of said electrodes will sway said beam, and one or more electrodes so placed and charged that in the operation of the tube they will intermittently emit secondary electrons, and one or more electrodes positively charged with relation to all other electrodes in the tube, for absorbing said secondary emitted electrons.

5. The combination within an electronic valve, of a source of electrons, one or more secondaryelectron-emitting electrodes held at a positive 1 potential with relation to said source of electrons, a control electrode, and a grid between said source of electrons and said secondary-electron-emitting electrodes held at such an electronegative potential with relation to said secondary-electron-emitting electrodes that it will shield the electrons in the vicinity of said control electrodes from the strong electropositive eld of said secondary-electron-emitting electrodes, and an electrode more electropositively charged than an'y others in the tube and placed behind the most electropositively charged secondary-electron-emitting electrode in the tube.

6. The combination within an electronic tube valve, of anelectron beam, a pair of electrodes so placed on opposite sides of the beam normally that a change of potential difference between said electrodes will sway saidv beam, one or more secondary-electron-emitting electrodes held at a distinctly positive potential with relation to the source of said electron beam, a pair of electrodes held at a more electropositive potential than all the other electrodes and also placed onV opposite sides of the normal position of said beam so that the one of the pair of most positively charged electrodes which is on the same side of the tube as `the input electrode at that instant deflecting the beam, will receive the greatest bombardment of secondary electrons from the secondary-electron-emitting electrode and a grid placed between said pair of input electrodes and the secondary-electron-emitting electrode and negatively charged with relation to said secondaryelectron-emitting electrode.

7. The combination in an electrical amplifying system .of an electronic tube valve having within it an electron beam, a pair of control electrodes so placed on opposite sides of the normal position of said beam that a change of potential difference of said electrodes will lsway beam that the one of the pair of most positively charged electrodes which is on the same side of the tube as the control platel at that instant deflecting the beam will receive the greatest bombardment of secondary electrons from the secondary-electron-emitting electrode, a grid placed between said pair of control electrodes and the secondary-electron-emitting electrode and negatively charged With relation to said secondaryelectron-emitting electrode, and a center-,tapped resistance or impedance whose extremities are connected each to one of the most positively charged electrodes in the tube and Whose centertap is given a potential in excess of that of any of the above electrodes.

8. The combination in a vacuum tubeelectronic valve of one or more secondary-electronemitting electrodes, separate means receiving said secondary emissions, an electron beam, a pair of input electrodes so placed that a change in potential diierence of said input electrodes will sway said electron beam, and a shield so placed and charged that the number of secondary electrons emitted from the rst named electrodes is varied by the position of the'electron beam with respect to the shield.

9. In combination with an inductance, a vacuum tube having spaced electrodes connected in series with said inductance and forming therewith a series resonant circuit, and a second inductance shunted across the said electrodes for decreasing the eiective capacitance between the said electrodes.

10. The combination in an amplifier, of means to produce an electron beam, means for utilizing variations in the input to cause said beam to sway, and means cooperating with said beam to produce intermittently therefrom a stream of secondary electrons.

11. Means for amplifying a pulsating electron stream, comprising locating one or more members in the path of said stream for emitting secondary electrons and means located beyond said members for collecting said secondary electrons, with means for maintaining said members relatively positive with respect to the electron source and means for maintaining said collecting means relatively positive to said members.

' MATTHEW S. HOPKINS, JR.

DISCLAIM E R 1,920,863.Maithew S. Hopkins, Jr., Washington, D. C. AMPLIFICATION oF RADI- ANT ENERGY. Patent dated Au 1936, by the patentes.

gust l, 1933. Disclaimer filed March 25,

Hereb enters this disclaimer to claim l1 in said specification.

[ 'al Gazeta April as, 1.936.]

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