US2240713A

US2240713A - Electron multiplier

Info

Publication number: US2240713A
Application number: US151440A
Authority: US
Inventors: Orthuber Richard; Steudel Eberhard
Original assignee: AEG AG
Current assignee: AEG AG
Priority date: 1936-07-07
Filing date: 1937-07-01
Publication date: 1941-05-06
Anticipated expiration: 1958-05-06

Description

R; ORTHUBER :rm. 2,240,713

ELECTRON MULTIPLIER May 6, 1941.

Filed July 1, 1957 INVENTORS RD ORTHUBE/Q HARD STEUDEL RIC/IA 585R BY HIGH . 6 FREQ EA/CY AMPLIFIER ATTORNEY Patented May 6, 19-41 ELECTRON nur'rrrrma Application July 1, 1937, Serial No. 151,440 In Germany July 7, 1936 10 Claims.

This invention relates to electron multipliers and more particularly, to the use of electron multipliers for providing an electron source for producing a beam of electrons in cathode ray tubes.

In accordance with the invention in using a multiplier in an intensity controlled cathode ray tube, the control of the cathode ray tube is carried out by a detuning of the multiplier. The detuning can be accomplished in accordance with the invention, by the variation of any of the quantities determining the electron current. A cathode ray tube so operated is used preferably as receiver apparatus for television purposes, but it may, however, also be used wherever intensity controlled cathode ray tubes are required.

The invention will be explained and described in detail referring to the drawing in which Fig. 1 shows one embodiment of the invention in which a dynamic multiplier is used to provide a source of electrons for a cathode ray tube and in which control is supplied by varying the anode voltage of the dynamic multiplier;

Fig. 2 shows a modification of the embodiment shown in Fig. 1 in which the control of the dynamic multiplier is effected by varying the potential of the cathodes of the multiplier;

Fig. 3 shows a further modification of the em bodiment shown in Fig. l in which a static electron multiplier is used instead of a dynamic multiplier; and

Fig. 4 shows another modification of the embodiment shown in Fig. 1 in which a cathode ray is used to control the electron multiplier.

Figure 1 shows a cathode ray tube with a multiplier of the so-called dynamic type as electron source. The control of the intensity is hereby obtained through modulation of the plate potentil. i and 2 represent the plates of the multiplier between which a high frequency alternating field is produced by means of a short wave generator and oscillatory circuit 3. The electron ray amplifled by the release of secondary electrons can enter through the hole t in the plate I into the reproducing system 5 of the cathode ray tube constructed in the ordinary manner. 6 represents the deflection elements. Furthermore, an anode 1 is provided between the plates of the multiplier.

It is known that the intensity of the current produced by electron multiplication largely depends on the voltage applied to the anode I of suitable shape of the multiplier. In accordance with the invention, therefore, the receiving potential supplied by the receiver 8 is applied to the anode. The anode furthermore may have a fixed or adjustable bias potential. The setting of the bias potential can be carried out by suitably choosing the tap point 9 at the oscillatory circuit 3, or by the insertion of a direct voltage source If When suitably choosing the frequency and amplitude of the alternating potential applied to the plate of the multiplier, as well as that of the bias potential of the plate. a small variation of the potential supplied by the receiver 8 causes a considerable variation in the plate current. The manner in which the said electrical constants are to be chosen in a'suitable way depends among other things on the geometrical shaping of the multiplier, and the values for theseelectrical quantities can, for instance, be taken from characteristic curves recorded in the known manner. The intensity control according to the invention has the advantage that a small amplification of the receiving potentials is suihcient. Thus, for instance, for modulation voltage variations in the order of 1 volt are sufficient. The steepness of the current voltage characteristic is further increased by the-high electron current that can be attained, and which is of the order of 10- amp.

- Figure 2 shows a further mode ci.co-nstruction of the arrangement according to the invention. In the cathode ray tube herein shown with a dynamic type multiplier as electron source, the intensity control takes place through modulation of the alternating voltage of the multiplier. The numbers I to l have the same significance as in Fig. 1. 1

The intensity of the multiplier current at constant plate potential, and frequency, depends as is known on the amplitude of the alternating potential existing between the plates. The same is true in the absence of the anode, for the case that the frequency is maintained constant. In accordance with the invention, therefore, the high frequency receiving potential is applied as multiplier potential to the plates l and 2. This is readily possible, for instance, in television receiving tubes, since the frequencies which the multiplier requires and which are used in television transmissions are generallyof the same order, namely, 50 megacycles. potential is increased to about 30 to 109 volts by the high frequency amplifier ii. The anode l of the multiplier can be omitted, but it may also have a fixed potential applied thereto, which may also be adjustable for controlling contrasts or brilliancy. This case is shown in Fig. 2, in

The receiving 7 which item i2 is a direct potential source and [3 an adjustable resistor.

The variation of brilliancy of the image point on the luminescent screen in accordance with the modulation of the receiving potential indicates a detuning of the multiplier at the same rate and periodicity as the variation of the brilliancy and hence a corresponding intensity control of the electron ray. For the use of the arrangement as receiving apparatus for television transmissions the particular advantage is that the synchronizing impulses impressed upon the carrier wave cause an especially strong detuning of the multiplier. It is possible so to design the multiplier, that it ceases functioning at this detuning, so that without further auxiliary means, a blocking of the returning electron ray is achieved. A' further advantage resides in that the detectors are not required, and that as receiver simply a highfrequency amplifier can be used.

According to a further idea of the invention, the relaxation potentials required for the productioii of the'image can be produced by means of a furthermultiplier, which is tuned to the ampli-.

tude of the carrier wave which is decreased or increased during the synchronizing impulses, and which multiplier is so constructed that it is ineffective during the remaining time i. e. during the passing of the image line.

In the same manner and same circuit as shown in Fig. 2, an arrangement, according to the invention can be used in case of intensity control through frequency modulation. Such an arrangement is useful if, for instance, the sending of television images is so carried out that the variation of the brilliance of the image point, causes a variation in the frequency.

In the hitherto described arrangements, dynamic type multipliers have been used in such mode of operation that the value of the derived electron current was determined only by the operating data independent of the originally present number of electrons, or eventually electrons released through stray light. In the following arrangements will be described in which the fact is utilized that the multiplier of dynamic type as well as that of static type can be so operated that the final current is proportional to the initial current or also to the'exposure of themultiplier. In the Figs. 3 and 4 two modes of con struction of the cathode ray tube according to the invention are shown by way of example.

Fig. 3 shows a cathode ray tube with a multiplier of the static type. 44 and I5 represent several plates of the static type multiplier of which I4 is the first plate and IS the second one on which electrons are released. shall be operated in the known manner, i. e. a magnetic field is provided directing the electrons from one plate to the other one in the manner shown by the curves l7, and whereby potentials are applied between the plates, which may for instance be supplied by batteries it. In accordance with the invention a grid I9 is ar ranged ahead of the plate l-t and to which are impressed the voltages controlling the intensity. The plate l4 needs not have the photoelectric effect, it may also be adapted as any other electron source, for instance, as glow cathode. The electron current supplied by I 4 is controlled by the potentials impressed upon the grid l9, and the current so controlled is amplified in the multiplier, so that finally the electron current leaving through the hole 4 reveals the desired brilliance variations. The degree of the ampliderive all potentials Hi from a single potential source across a potentiometer.

Instead of controlling the electron current by means of a grid placed ahead of the first plate, this can also be done in that, for instance, the value of the potential existing between two or a greater number of multiplier plates, is modu lated, or in that the magnetic field which curves the electron path is modulated. Figure 4 shows an arrangement in which dynamic multiplier supplies an end current which is proportional to the initial current. The plate 2 of the multiplier has an aperture 2% through which there enters into the multiplier an elec- The multiplier I tron ray supplied from a constant electron source 2!. The control potential is here applied to a deviation element 22 which sends the electron current past the aperture 20, so that the intensity entering the multiplier corresponds to the control potential. Also in this case it is necessary so to arrange the degree ofamplification of the multiplier that the electrons passing through the aperture 4 have the intensity necessary for recording on the fluorescent screen.

An advantage of the arrangement according to the invention is the long life of cathode ray tubes equipped with a multiplier as compared with tubes having glow cathodes. In addition thereto, such a tube resists much more favorably mechanical vibrations and the like.

In order to attain a sufficiently high electron amperage in cathode ray tubes, in which a multi plier is used as electron source, it is not necessary that the plates I and 2, or i4, E6 of the multiplier have a layer with specially high emission property. In many cases it is sulficient to utilize plates which are not combined, and

whereby aluminum or beryl were found to be especially favorable. The operation of such a tube becomes especially simple. For exceptional requirements it is of course advisable to provide the plates of the multiplier with a layer having a high emission property.

\Vhat we claim is: 1. A cathode ray tube system' comprising a dynamic secondary electron multiplier having a plurality of secondary emissive electrodes, a tar get electrode positioned in register with said multiplier and spaced longitudinally therefrom, means to withdraw electrons from said multiplier, means to direct toward and focus upon said target electrode the withdrawn electrons, means interposed between said multiplier and said target electrode for producing a deflection of the focused electrons in two mutually perpendicular directions across said target electrode, means to receive signalling energy, and means to vary the electron multiplication ratio of the multiplier in accordance with the received signalling energy.

2. A cathode ray tube system comprising a dynamic secondary electron multiplier having a plurality of secondary emissive electrodes, 2. target electrode positioned in register with said multiplier and spaced longitudinally therefrom, means to withdraw electrons from said multiplier, means to direct toward and focus upon said target electrode the withdrawn electrons, means interposed between said multiplier and said target electrode for producing a deflection of the focused electrons in two mutually perpendicular directions across said target electrode, means to receive signalling energy, and means to vary the electron multiplication ratio of the multiplier in accordance with the fre quency of the received signalling energy.

3. The method of reproducing images upon a luminescent screen which comprises the steps of releasing electrons from a source, producing secondary electrons by the released electrons, multiplying the produced secondary electrons, re ceiving signalling energy, controlling the multiplication ratio of the produced secondary electrons in accordance with the received sig nalling energy, focusing the multiplied electrons upon the luminescent screen, and deflecting the focused electrons in two mutually perpendicular directions across said screen.

4. The method of reproducing images upon a luminescent screen which comprises the steps of releasing electrons from a source, producing sec- I ondary electrons by the released electrons, multiplying the produced secondary electrons, receiving signalling energy, controlling the multiplication ratio of the produced secondary electrons in accordance with the frequency of the received signalling energy, focusing the multiplied electrons upon the luminescent screen, and deflecting the focused electrons in two mutually perpendicular directions across said screen.

5. The method of reproducing images upon a luminescent screen which comprises releasing electrons from a source, producing secondary electrons by the released electrons, multiplying the produced secondary electrons, receiving signalling energy representative of an image to be reproduced, said signalling energy being interspersed with synchronizing signals, controlling the multiplication ratio of the produced secondary electrons in accordance with the signals representativ of the image to be reproduced, reducing the multiplication ratio to zero upon the receipt of said synchronizing signals, focusing the multiplied electrons upon said luminescent screen, and deflecting the focused electrons in two mutually perpendicular directions across said screen.

6. A cathode ray tube system comprising a dynamic secondary electron multiplier having a plurality of secondary electron emissive electrodes, a luminescent screen in register with and displaced longitudinally from said multiplier, an electron optical system positioned in register with and intermediate said multiplier and said screen, an electron beam deflecting system positioned intermediate said electron optical system and said screen, means for receiving signalling energy and connections from said receiving means to said multiplier to control the multiplication of said multiplier in accordance with the frequency of the received energy.

'7. A cathode ray tube system comprising a dynamic secondary electron multiplier having a plurality of secondary electron emissive electrodes, a luminescent screen in register with and displaced longitudinally from said multiplier, an electron optical system positioned in register with and intermediate said multiplier and said screen, an electron beam deflecting system positioned intermediate said electron optical system and said screen, means for receiving signalling energy and connections from said receiving means to said multiplier to control the multiplication ratio of said multiplier in accordance with the received energy.

8. A cathode ray tube system comprising a dynamic secondary electron multiplier having a plurality of secondary electron emissive electrodes, a luminescent screen in register with and displaced longitudinally from said multiplier, an electron optical system positioned in register with and intermediate said multiplier and said screen, an electron beam deflecting system positioned intermediate said electron optical system and said screen, means for receiving signalling energy and connections from said receiving means to said multiplier to control the multiplication ratio of said multiplier in accordance with the frequency of the received energy.

9. A cathode ray tube system comprising a dynamic secondary electron multiplier having a plurality of secondary electron emissive electrodes, a luminescent screen in register with and displaced longitudinally from said multiplier, an electron optical system positioned in register with and intermediate said multiplier and said screen, an electron beam deflecting system positioned intermediate said electron optical system and said screen, means for receiving signalling energy, a resonant circuit connected between two of said plurality of electrodes, and means to transfer energy from said receiving means to said circuit to control the multiplication ratio of said multiplier in accordance with the received energy.

10. A cathode ray tube system comprising a dynamic secondary electron multiplier having a plurality of secondary electron emissive electrodes, a luminescent screen in register with and displaced longitudinally from said multiplier, an electron optical system positioned in register with and intermediate said multiplier and said screen, an electron beam deflecting system positioned intermediate said electron optical system and said screen, means for receiving signalling energy representative of an image to be reproduced interspersed with synchronizing signals, a resonant circuit connected between two of said plurality of electrodes, and means to transfer energy from said receiving means to said circuit to control the multiplication ratio of said multiplier in accordance with the image energy and to reduce the multiplication ratio to zero in accordance with the synchronizing signals.

RICHARD ORTHUBER. EBERHARD S'I'EUDEL.