US3609595A - Beam-control semiconductor oscillator - Google Patents

Abstract

An electron beam high frequency generator and circuit arrangement in which a pencil of electrons (i.e., an electron beam) is trained at an acute angle against an elongated semiconductor bar in series with a current source and an electrode. A pair of deflector plates flank the beam to provide static or varying spreading of the latter while a grid permits control of the beam current and, therefore, the frequency of the device. By applying varying potential to the deflector plates, a modulation is superimposed upon the carrier frequency.

Description

United States Patent [72] Inventor Kiyoshi lnoue 100 Sakato, Kawasaki, Kanagawa, Tokyo, Japan [21 Appl. No. 603,971 [22] Filed Dec. 22, 1966 [45] Patented Sept. 28, 1971 {32] Priority May 12, 1966, June 11, 1966 [3 3] Japan [31] 41/30181 and41/37634 [54] BEAM-CONTROL SEMICONDUCTOR OSCILLATOR 5 Claims, 10 Drawing Figs. [52] 0.8. CI 332/25, 331/107 R, 313/65 AB, 332/16, 313/64, 313/311 [51] Int. Cl ..H01j 31/58, 1103c 3/34, 1103b 5/12 [50] Field of Search 313/89, 65 A; 330/33; 315/31; 331/107, 107 G; 332/25 [56] References Cited UNITED STATES PATENTS 2,540,490 2/ 1951 Rittner 330/33 2,588,292 3/1952 Rittner et a1 313/89 X 2,589,704 3/1952 Kirpatrick et a]... 313/89 X 3,344,300 9/1967 Lehrer et a1. 313/89 X 2,678,400 5/1954 McKay 313/68 3,144,575 8/1964 Babits.... 313/65 A 3,230,473 1/1966 Adler 330/4.7 X

Primary Examiner-Robert Sega] Attorney-Karl F. Ross ABSTRACT: An electron beam high frequency generator and circuit arrangement in which a pencil of electrons (i.e., an electron beam) is trained at an acute angle against an elongated semiconductor bar in series with a current source and an electrode. A pair of deflector plates flank the beam to provide static or varying spreading of the latter while a grid permits control of the beam current and, therefore, the frequency of the device. By applying varying potential to the deflector plates, a modulation is superimposed upon the carrier frequency.

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, i BEAM-CONTROL SEMICONDUCTOR OSCILLATOR My present invention relates to a beam-control electronic device, and, more particularly, to a high current vacuum tube suitable for use in switching, amplifying, electronic display, or the like.

Beam-type vacuum tubes of conventional character can be divided into two categories, namely amplifying arrangements and display devices. In an amplifying system of the usual type, a thermionic emitter is energized directly or indirectly to produce electrons which drift from a cathode to an anode, e.g. the plate of the vacuum tube, under the intervening control of one or more grids maintained at various potentials so as to regulate the current-carrying capacity of the electron cloud or stream. in practice, therefore, the amplification characteristics are determined by the density of the electron cloud and, of course, the current represented thereby. The application of relatively small potentials and electric currents to the control grids permits a relatively small amount of energy (the grid-dissipation power) to regulate a comparatively large amplitude (e.g. the current-carrying capacity to the electron beam). Devices of this type are prone to malfunction because of thermal considerations and have current-carrying capacities which are limited by technical considerations in this respect. In fact, the amount of heat generated at the anode or plate by kinetic impact of the impinging beam thereon is directly related to the current carried by the beam so that heat sinks, gas or liquid cooling means and the like must be provided for the higher power tubes. Even with such expedients, difficulties are encountered since higher energy and amplitude electron beams produce mechanical erosion with deterioration of the grids, the cathode and the anode.

In display-type devices, such as cathode-ray tubes, the electron beam does not necessarily impinge upon a plate, so that the kinetic energy of the beam is dissipated at this anode, but is projected against a fluorescent surface which is energized by the beam and creates visible light. In this case, the usual control grids are provided to switch the beam on and off while regulating the amplitude (beam current) of the beam and the illumination produced thereby. Acceleration of the electron cloud is effected by anodes forwardly of the grids and orientation of the beam is determined by deflecting plates, In such beam devices, it is also a common practice to use magnetic fields to focus, concentrate, deflect or disperse the beam and, indeed, magnetic lenses of various types are available for this purpose.

In all such systems, the controlled current is in effect the beam current and thus the electron current passing through the tube. While relatively higher grid currents are necessary to regulate the principal current flow, this latter is limited by mechanical considerations.

It is therefore the principal object of the present invention to .provide a beam-controlled electron tube in which the controlled current is not limited by the electron current of the beam, which has a longer life than conventional tubes with control of correspondingly larger current flows, and has greater flexibility than conventional beam-power tubes.

Another object of this invention is to provide a high response, high current vacuum tube having a relatively high impedance at the control element such that larger currents can be regulated with low control power.

Still another object of this invention is to provide a system for controlling the power supply of an electrochemical machining or electric discharge machining process with greater accuracy and efficiency than has been possible heretofore.

Still another object of my invention is to provide a display tube with better control than has been possible with conventional cathode-ray systems.

These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, with a vacuum-tube system in which an electron beam acts as the control element of a solid-state three-element switching device. Thus, if the solid-state switching system can be considered to be the equivalent of a transistor of high current-carrying and switching capacity, the solid junction or sandwich-type control layer being sensitive to photon energization, a electron beam is directed against the solid-state body such that it regulates the current flow characteristics between the collector and emitter (if the system is of transistor type), between the anode and the cathode (e.g. if the system is of the controlled-rectifier type), or between the terminals of a resistance element (e.g. when the system is of the photoresistive or photoconductive type).

In practice, the solid-state element will have at least two terminals and a resistivity characteristic modifiable by the impinging electron beam and will be disposed in the path of such a beam which may be generated by a conventional electron gun or other thermionic source. According to this invention the electron gun is itself provided with one or more control grids and/or high voltage beam-deflection means for regulating the intensity of the electron beam or its orientation and thereby controlling the conductivity characteristics of the solid-state device. Since a relatively low beam current can serve to switch comparatively large solid-state currents, the thermal dissipation of the vacuum tube will be much less than the dissipation required in beam-power tubes in which the full controlled current appears as the electron current flow. Furthennore, a still smaller energy is necessary at the grid or deflection plate since the very nature of the beam is one involving amplification of whatever parameter has been applied thereto. Thus, the control grid of the electron gun can have an extremely high impedance input and require very meager control power by comparison with the beams and energy necessary for conventional beam-power tubes.

According to another aspect of the present invention, the electronic device is used to generate a high frequency pulse or a periodic fluctuating output by repetitively sweeping an electron beam against a longitudinally extending solid-state element energized with direct current. If this elongated element is connected at terminals at its opposite ends with a DC source and a load, the electron beam sweeping along this element from one side to the other will cause, in effect, an electron drift (i.e. of excess electrons) in the direction of the sweep of the beam or will progressively cancel electron depletion of the semiconductor as it sweeps thereacross. As a consequence, the load current will appear as a series of pulsations at the cadence of the sweep of the beam. By properly timing and controlling the beam-sweep rate, the generator can be used effectively as a variable-frequency oscillator of substantially any output with considerable insensitivity to transients, since neither the time-control elements, nor the solid-state device are hypersensitive thereto. Since the current-carrying capacity of the solid-state device is only a function of the characteristic of the semiconductive material employed, the oscillator can control relatively high powers without difilculty. Moreover solid-state control of high frequency signals is possible.

Another feature of this invention resides in the provision of a variable-frequency oscillator using a semiconductor in the manner generally described above. I have discovered, in accordance with this aspect of the invention, that a continuous electron beam directed against an elongated semiconductor body at an acute angle will cause the state of the body to switch periodically at high frequency between a conductive state and a nonconductive state. Thus, when the semiconductor is connected in series with a source of electric current and a load, a high frequency current will'be applied to the latter at a frequency determined by the beam current impinging upon the semiconductor.

According to yet another aspect of this invention, the electron-beam-controlled conductivity of a semiconductive substance is used to intensify the image displayed upon a television screen. The phosphors used upon the screen, in this case, are not only energized by the electron beam but are intensified in their fluorescent output by an electroluminescent effect. For this purpose, the phosphor is laminated to the semiconductive layer between a pair of electrodes anda source of direct current or pulsating current connected across the laminate. Normally, the semiconductor is in a nonconductive state and no emission-intensifying current passes through the phosphor. when, however, the phosphor is activated by the electron beam at a particular region of the screen, the translumination of the immediately adjoining semiconductor material renders this region of the switching layer conductive so that an electroluminescent intensification of the emission results from the passage of current through the semiconductor or phosphor layers.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. l is a diagram of a beam-control tube in accordance with the present invention;

FIG. 2 is a graph showing some of the characteristics of this tube;

MG. 3 is a circuit diagram of a system for the electricdischarge machining of a workpiece and using an electronbeam tube of the present invention;

FIG. 8 is a diagram of another tube arrangement embodying these principles;

FIG. 5 is a diagram of a high frequency generator using an electron beam as the control means;

FIGS. 5A and 5B are graphs showing characteristics of the tube of FIG. 5;

FIG. 6 is a view similar to FIG. 5 of another embodiment of this invention;

FIG. 7A is a diagram of a cathode-ray television tube for the display of color images according to this invention; and

FIG. 7B is a cross section of the face of this tube drawn to an enlarged scale and illustrating certain principles of the inventron.

In FIG. 1 I show an amplifier-type beam-power tube which is here illustrated in diagrammatic form. The evacuated tube 10 has a filament or heater 11 which serves to raise a thermionic-emission cathode 12 to a temperature sufficient to cause the latter to emit electrons. juxtaposed with cathode 12 on the opposite side of an electron-drift space 13, I provide an anode 14 in the form of a plate of semiconductive material to which a pair of terminals are spacedly fused at 15 and 16. In effect, therefore, the terminals 15 and 16 can be considered equivalent to the emitter and collector of a transistor or to the anode and cathode of a solid-state controlled rectifier switch in which the plate 14- controls flow of current through the junctions of the terminals and the plate and, therefore, between the electrodes. If the photon-activatable semiconductive body 14 is only a photoresistive material, the terminals 15 and I6 are interchangeable in function and can be connected in series with any load (e.g. as shown at 15') to be controlled by varying the resistivity of the semiconductor device 14-16.

Between the cathode 12 and the semiconductive plate 14 of the vacuum tube, I provide the usual control grid 17 and, as is common in beam-power tubes, a screen grid 18. While an electron-accelerating circuit may be provided at B to promote the electron flow between a cathode and an anode, it will be understood that the screen grid 18, which has been provided with a relatively positive potential by comparison with the cathode, can also have an accelerating function.

Input is through the control grid 17 as represented at I, the controlgrid being maintained at a potential below the potential of the cathode in the usual manner. Thus when the grid 17 is so poled as to prevent electron drift in the direction of the plate 14, the semiconductive device 14-16 can be totally nonconductive or cut off to prevent any current flow between the terminals 15 and 16.

In FIG. 2, I show the characteristics of such a system using a cadmium sulfide semiconductive plate 14, a plate voltage from battery B of 600 volts and an output as represented along the ordinate. Along the abscissa, I have plotted the beam current in microamperes. Thus it can be seen that a current flow between the terminals 15, 16 of 0-500 milliamps (0 to 0.5 a.)

can be controlled with a beam current ranging between 0.01 and 0.07 microamperes and a fraction of this current at the grid. I-leat dissipation is no longer a problem while a reduced dimensioning of the entire system is possible.

EXAMPLE I Using a tube of the type illustrated in FIG. 1 with a plate voltage of 600 volts, a cadmium sulfide anode 14 as the plate, a control grid and a screen grid as illustrated in FIG. 1, the plate resistance was found to be variable between 2,000 ohms and 24 ohms. With the aid of the control grid 17, the beam or electron current between cathode l2 and plate 14 was varied from 0.01 to 0.07 microamperes to yield outputs through the plate 14 as shown along the ordinate of FIG. 2. Similar results were obtained when the cadmium sulfide plate 14 was replaced by semiconductive materials from the following group: silicon, germanium, gallium arsenide, silicon carbide, cuprous oxide, zinc sulfide, lead tritelluride, lead sulfide, indium phosphite, aluminum antimonide and indium antimonide.

It will be understood, of course, that the beam-power tube of FIG. 1 can be used in substantially any semiconductive circuit with a degree of amplification selected by modifying the plate voltage and the input signal applied to the control grid 17.

In FIG. 3, I show an electron-beam tube as incorporated in an apparatus for regulating the power of an electric discharge machining (EDM) system. It will be understood that the system is also applicable whenever control of relatively high current pulses is required with a triggering system of low capacity designed to feed into a high impedance controlling device.

In the system of FIG. 3, the beam-power tube is evacuated and contains a heater 11] across which an A battery 121 is connected to represent any source of heater current. This heater or filament raises the temperature of a thermionicemitting cathode 112 which is connected to the negative terminal of the plate supply 5" battery 122 whose positive terminal is connected via a balancing potentiometer 123 to a pair of deflecting plates 124, 125 which are normally at precisely the same potential so as to ensure undeflected passage of the electron beam. The plates 124, 125 here act as accelerating anodes for the electron beam which, because of its high velocity and kinetic energy, impinges upon a semiconductive electron-activatable body 114 whose terminals 115 and 116 are connected in series with the power supply for an electricdischarge machining apparatus 126. A focusing shield 127 is provided adjacent the cathode 112 and is maintained at a positive potential somewhat above that of the cathode by a battery 128. The tube 110 also is formed with a control grid 117 which serves to switch the electron beam under the control of a triggering device 130 which may have a very high output impedance and be of low power. The triggering device is here constituted as a transistor multivibrator whose PNP transistors 131, 131 are connected in the usual free-running multivibrator network with a pair of RC networks 132 determining the pulse frequency and duration. The multivibrator 130 has a supply voltage source such as a battery 133. The transistor 131' thus acts as an amplifier and has its emitter-collector terminals in series with a biasing C battery 129 and the control grid 117. The battery 129 is returned to the cathode.

The semiconductive variable-resistance block or plate 114, which is disposed in the path of the electron beam or cloud, is connected in series with the EDM power supply represented as a battery the electrode system, here illustrated diagrammatically, is a machining electrode 141 and a vessel 142 retaining the dielectric medium and serving as a support for the workpiece.

A pulse-shaping resonating network of inductances 143 and capacitances 144 is connected across the EDM machining system 141, 142 in order to promote the development of electric discharges thereacross. When the electron beam of tube 110 is pulsed by the application of electric pulses at high frequency to the grid 117 by the multivibrator 130, the semiconductor 114 is rendered operative and closes a circuit through the battery 140 and the machining gap formed between the electrode 141 and the workpiece. Current surges from capacitors 144 are superimposed upon the discharge produced by the instantaneous conductivity of the semiconductor 114. I have found that with a cadmium sulfide plate 114 having a thickness of 2 mm. and using a control current of microamperes to I00 microamperes at the grid 117 it is possible to control a current flow in the EDM circuit of 250 amperes at 50 volts of the source 140. Accurate control is provided even at frequencies greater than 55 kilocycles/sec.

A feedback regulation of the power can be supplied by another grid 118 which is biased by a feedback amplifier and sensor 145.

The arrangement illustrated in FIG. 4 represents a modified tube for operating in sequence a multiplicity of EDM, ECM or other material removal systems or for generating pulsing currents therefore. The tube of FIG. 4 comprises an evacuated envelope 210 whose cathode 212 is heated by a filament 211 and is part of an electron gun including a focusing plate 227, a control grid 217, a feedback grid 218 and a pair of deflector plates 224 and 225 respectively flanking the electron beam or pencil which is represented by the dot dash line 246.

In this system, the semiconductive plate 214 is subdivided into a plurality of zones 214a, 2l4b and 214c in a direction transverse to the beam in which the beam may be deflected by electrostatic potentials applied to the plates 224 and 225. A common electrode 214d is provided for all the sections 214a-2140 and consists of a vapor-deposited metal foil substantially transparent to electron irradiation. This conductive layer 214d can be connected with the B+ terminal of the battery 222 (whose B-terminal is connected with the cathode 212) as well as with one side of the machining source 240. Each of the sections 2140, 214k and 2140 can be connected with a respective electrode similar to that shown at 141 in FIG. 3 of a respective machining arrangement or to the respective portion of a single electrode. The other side of battery 240 is, of course, connected to the other terminal of the machining system. It will be apparent, therefore, that when the electron pencil or beam 246 is deflected laterally (arrow 247) by the application of suitable polarities to the deflector plates 224 and 225, the beam 246 will sweep successively or alternately into impinging relationship with each of the semiconductive sections 214a-214v which are electrically insulated from one another. These sections will be rendered conductive in turn.

When, for example, an alternating current is applied across the deflector plates 224, 225 from the sweep-voltage source 230, a three-mode operation can be discerned. In the first mode, the plate 224 is relatively positive and the plate 225 relatively negative during part of each cycle such that the beam 246 is deflected to impinge upon the section 214a and render the latter conductive. The machining electrode connected with this section is then triggered as described with reference to FIG. 3. During the opposite portion of the cycle the deflecting plate 224 is relatively negative and plate 225 relatively positive whereupon the beam impinges upon the section 2140 to energize its electrode or electrode portion. During the intervening period, the beam 246 sweeps across the section 214b and energizes its electrode or electrode portion. Thus if all three sections 214a-2140 are connected to a single electrode, three pulses will be delivered of amplifying current for each cycle of the control current supplied to the deflecting plates 224.

The magnitude of the current flowing to the machining system will depend upon the bias at the grid as previously indicated. The triggering source 230 can, however, be pulsed to alternately energize the deflector plates 224, 225 so that, in the unenergized position of the plates, the beam impinges upon section 2141: whereas alternate energization of the plates 224. 225 causes deflection of the beam 246 to the-corresponding side with energization of the sections 214a and 214b for the duration of the energizing pulse.

In FIG. 5, I show a modified beam-tube system according to the present invention wherein the evacuated envelope 310 encloses an electron gun consisting of a filament or heater 31 1, a cathode 312 adapted to be brought to thermionic emission temperature by the heater, a control grid 317 in the path of the electron beam (diagrammatically represented by its axis 346), and an anode formed by a pair of deflecting plates 324 and 325. The heater 311 is connected to the usual A" battery 321 while a 8" battery or other source 328 has its negative terminal tied to the cathode 312 while its positive terminal is connected via the wiper of a balancing potentiometer 323 to the deflecting electrodes 324 and 325. The level of the positive potential at these deflecting electrodes can be set by adjustment of the potentiometer 323 so that the spread of the electron beam 346 can be controlled and the beam caused to impinge at an acute angle upon a semiconductor body 314. The latter may be composed of cadmium sulfide and may have a length of, say, 20 mm., a width of 1 mm. and a thickness of about 0.5 mm. so as to constitute a bar of photoconductive material in the plane of the axis of the beam.

The terminals 315 and 316 of the semiconductor bar 314 are joined to plates 315a and 316a printed onto the semiconductor or otherwise retained as electrodes thereon. The terminals are connected in a load circuit including a source of electric current, such as the battery 340, and a resistance 341 representing any load requiring a high frequency input. The electron beam 346 is trained at an acute angle a, of 30 to a, of 12 as shown in FIG. 5) to the semiconductor bar 314, it has been found that the impingement of a high energy electron beam at an acute angle upon a P-type, N-type or an impuritytype semiconductor will induce an oscillation of the current carriers within the layer and thus constitute of the semiconductor a high frequency generator. As can be seen in FIG. 5, the beam includes the acute angle with the bar in the direction of impingement of the beam.

The frequency of the generator can be controlled by varying parameters of the electron beam, namely, its energy and velocity and the number of particles, with the aid of the control grid and the plate voltage. Thus I have discovered that the high frequency output across the load 341 varies in frequency with the plate current of the system and with the number of electrons constituting the beam.

EXAMPLE II In FIG. 5A, I show a graph in which the high frequency output across the load 341, in kilocycles per second, is plotted as the ordinate against the plate current in microamperes (plotted as the abscissa). The curve was obtained with a plate voltage of 200 VDC using a cadmium-sulfide semiconductor with the dimensions given earlier. It can be seen, therefore, that the output frequency of the system varies with the beam current and thus the number of electrons permitted by the grid 317 to pass. With the aid of conventional circuitry for modifying the grid potential, the system can be used to selectively generate a wide range of frequencies. In FIG. 58, I have plotted the output current in milliamperes (at 500 kilocycles per second for purposes of example) as the ordinate against the plate voltage as the abscissa. From this graph, it is apparent that the output power, as well as the output frequency, can be selectively adjusted within a wide range.

In FIG. 6, there is illustrated a modified oscillator system according to the present invention, which embodies principles described in connection with FIGS. 4 and 5. In this system, the evacuated envelope 410 again provides an electron gun training a beam 446 of electrons upon the semiconductive bar of plate 414. The electron gun includes the heater or filament 411, a cathode 412, a control grid 417 and an anode formed by a pair of deflection plates 424 and 425 flanking the beam 446. The electron-responsive semiconductor 414 is connected in circuit with a battery 440 and the load 441. As illustrated in FIG. 6, however, an AC source 430 of low power but adjustable frequency is inductively connected at 4300 in circuit with the plate source 428 and the deflecting plates 424 and 425.

Thus, in addition to the natural oscillation of the current-carrying means of the semiconductor 414, as described in connection with FIG. 5, the electron beam 446 is spread and contrasted in the direction of arrow 447 across the length of the semiconductor to superirnpose upon the natural frequency determined by the plate current and beam power, a modulating alternating current determined by the oscillation frequency of the source 430.

The present invention also is applicable to cathode-ray tubes of the display type, for analog-to-digital conversion, or the like. In an analog-to-digital conversion, the analog parameter is used to deflect the beam (e.g. as indicated in FIG. 4) and thus sweeps it across a plurality of semiconductors, thereby providing an output at each of them capable of digital process. In the improved system of the present invention, an amplified current flow is provided when the semiconductive bodies are connected in series with the battery or other source and an amplified pulse is obtained upon energization.

It is possible, moreover, to obtain a light amplification using similar techniques as illustrated in FIGS. 7A and 7B. In FIGS. 7A and 7B, 1 show a cathode-ray television picture tube for the display of color images, As is conventional, the picture tube comprises an evacuated glass envelope 510 having a screen 514 at its forward end. A magnetic deflecting yoke is represented at 550 and is disposed forwardly of the three electron guns adapted to respond to primary colors (e.g. red, blue, green and yellow). Each electron gun includes a respective filament or heater 511, a cathode 512, a control grid 517 representative of the several grids normally provided in such systems, the plate 527 and the usual focusing and sweep deflectors 524a and 524k disposed in pairs flanking the respective electron beams. The anodes 524a, of course, represent the vertical-sweep electrodes while plates 5241; represent the horizontal sweep electrodes. Insofar as the aforedescribed structure is concerned it is conventional and need not be discussed fully. The color kinescope tube has a phosphor dot screen upon the inner surface of its face plate, the screen 514 being of a laminated construction. Thus, as can be seen in FIG. 78, a vapor-deposited electrode layer 515a of aluminum, tin, copper or silver (transparent to electron irradiation) is provided inwardly of an electron-activatable semiconductor layer 514a of cadmium sulfide, zinc oxide or zinc cadmium sulfide.

A further layer 551 of the conventional phosphor then underlies the semiconductive layer 514a while a final electrode layer 5160 (transparent to visible light) forms the final electrode of the laminate adjacent the faceplate 552 of the picture tube 510.

A DC source 540 is connected in series with a high frequency alternating current source 540a between the terminals 515 and 516 respectively connected with the electrode layers 515a-516a. In this system, the electron-activatable material 514a (which may not respond to X-rays or photons) or photons acts as an electronic switch energized by the electron beam to increase or decrease the current flow through an energized portion of the phosphor 551 which is electroluminescent and, therefore, glows with the desired color and an intensity augmented by the electric energizing current from sources 540 and 5400. Thus, by contrast with conventional color tubes for television display, which produce images of an intensity directly related to the energy of the electron beam and photon or X-ray image intensifiers and also requiring high beam currents and accelerating voltages, the present invention can make use of only limited beam currents and obtain an intensive phosphorescence by the electroluminescent efiect controlled by the semiconductive layer 514 a. In this respect, therefore, the layer 514a serves as a control device regulating the current flow through a load (the electroluminescently intensifiable phosphor 551) and controlled in turn, by the electron beam which serves the double purpose of energizing the phosphor and triggering the semiconductor switching device.

EXAMPLE III In practice, the system of H68. 7A and 78 has been found to be operative when the outer layer 515a of conductive material transparent to the electron beam has a thickness of about 200 angstrom units and is composed of aluminum, copper, silver or tin, when the semiconductive layer 5140 of cadmium sulfide, zinc oxide or zinc cadmium sulfide has a thickness of 10 microns, when the phosphor layer 551 consists of one or more of the phosphors of the following table (with the doping substance indicated with the color) for the respective colors and having a thickness of about 10 microns, when the vapor-deposited electrode layer 5160 is composed of aluminum, copper, silver or tin and has a thickness of 200 angstroms, and when the sources 540 and 540a have a voltage and a frequency of volts and l kilocycle per second respectively.

The invention described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the appended claims.

I claim:

1. An electronic device comprising an envacuated envelope; an elongated semiconductor member in the path of said beams, said member being composed of an electron-activatable material of a degree of conductivity variable in dependence upon the intensity of a stream of electrons impinging thereon; an electron gun in said envelope trained permanently on said member for projecting thereupon an electron beam always at an acute angle with a surface of said member in the direction in which said beam is projected thereagainst; deflector means for spreading said beam between said gun and said surface while maintaining the axis of the beam continuously inclined to said surface at an acute angle; and means for connecting said semiconductor member at its ends in circuit with a source of electric current for energization of a load said means including terminals affixed to said member at locations spaced therealong in the direction of impingement of said beam whereby said member switches between relatively conductive and relatively nonconductive states at a high frequency determined by said intensity.

2. The device defined in claim 1 wherein said axis and said member are generally coplanar and said electron gun includes a thermionically emissive cathode, and a control grid forwardly of said cathode in the path of said beam, said device further comprising control means connected to said grid for varying said intensity.

3. The device defined in claim 1 wherein said deflector means comprises a pair of deflecting electrodes of variable electrical polarity for spreading said beam prior to its impingement upon said member.

4. An electric circuit including the electronic device of claim 1 wherein said member is a semiconductor bar and said electron gun includes a thermionically emissive cathode for generating said beam, at least one control grid in the path of said beam for varying selectively the beam current, and means along the path of said beam for accelerating the electrons thereof toward said semiconductor member, said circuit including means connecting said source of electric current and said load in series with said semiconductor member.

Claims (5)

1. An electronic device comprising an envacuated envelope; an elongated semiconductor member in the path of said beam, said member being composed of an electron-activatable material of a degree of conductivity variable in dependence upon the intensity of a stream of electrons impinging thereon; an electron gun in said envelope trained permanently on said member for projecting thereupon an electron beam always at an acute angle with a surface of said member in the direction in which said beam is projected thereagainst; deflector means for spreading said beam between said gun and said surface while maintaining the axis of the beam continuously inclined to said surface at an acute angle; and means for connecting said semiconductor member at its ends in circuit with a source of electric current for energization of a load said means including terminals affixed to said member at locations spaced therealong in the direction of impingement of said beam whereby said member switches between relatively conductive and relatively nonconductive states at a high frequency determined by said intensity.

2. The device defined in claim 1 wherein said axis and said member are generally coplanar and said electron gun includes a thermionically emissive cathode, and a control grid forwardly of said cathode in the path of said beam, said device further comprising control means connected to said grid for varying said intensity.

3. The device defined in claim 1 wherein said deflector means comprises a pair of deflecting electrodes of variable electrical polarity for spreading said beam prior to its impingement upon said member.

4. An electric circuit including the electronic device of claim 1 wherein said member is a semiconductor bar and said electron gun includes a thermionically emissive cathode for generating said beam, at least one control grid in the path of said beam for varying selectively the beam current, and means along the path of said beam for accelerating the electrons thereof toward said semiconductor member, said circuit including means connecting said source of electric current and said load in series with said semiconductor member.

5. The electric circuit defined in claim 1, further comprising means for varying the electrical potential of said deflector means for applying a modulation to the frequency determined by said intensity of said beam.

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