US2096415A - Electron discharge device - Google Patents

Description

Oct. 19, 1937. H. w. WEINHART ELECTRON DISCHARGE DEVICE Filed Dec. 27, 1933 2 Sheets-Sheet l //V|/ENTOR fin. WE/NHART MAM 7M A TTORNE V Oct. 19, 1937. H. w. WEINHART ELECTRON DISCHARGE DEVICE Filed Dec. 27, 1933 2 Sheets-Sheet 2 FIG. 5A

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UNITED STATES ELECTRON DISCHARGE DEVICE Howard W. Welnhart, Elizabeth, N. 3., asaignor to Bell Telephone laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 27, 1933, Serial No. 704,101

8 Claims.

This invention relates to electron discharge devices and more particularly to a device of the type in which a cathode ray beam is projected toward a fluorescent screen on one end of the device.

In an evacuated cathode ray device in which it is desired to focus electrons projected from an vessel evacuated to a high degree in which gas ionization is wholly eliminated so that all the electrons emitted by the emission source reach the fluorescent screen in a small and well defined spot.

Another object of the invention is to control the focusing of the beam by a system of electron optical lenses to insure concentration of the beam of electrons.

These and other objects may be attained in accordance with this invention in an enclosing vessel which is evacuated to a very high degree and in which no gas is present to form an ionized sheath to affect the focusing of the cathode ray beam. The vessel is provided with a stem at one end from which the main electrodes are supported and with a fluorescent screen at the other end which becomes luminous at the spot struck by the electrons so that deflections of the beam, due to impressed forces, can be seen or 5 photographed. The electrode structure for producing the cathode ray beam comprises an electron source or emitting cathode supported by the stem in the axis of the vessel and surrounded by a tubular shield having a closure at one end provided with a central aperture. An enclosing chamber is superimposed on the tubular shield and overlaps it to avoid stray paths for the electrons to the wall of the vessel. This chamber supports a tubular anode in the axis of the vessel and two baflle plates spaced apart in the chamber between the anode and tubular shield form a trapping enclosure for any stray electrons which are not projected axially through the aperture in the bafile plate adjacent the anode. The anode is of sufficient length to compel the electrons to follow an axial path in the form of a pencil or beam. When the beam emerges from the end of the anode it is electrostatically controlled by a long tubular member which has one end overlapping the anode. When the beam emerges from the end of the long tubular member it is further acted upon by a second electrostatic member that may be in the form of a conductive coating on the wall of the glass, or a second metallic cylinder overlapping the end of the first electrostatic mem- 5 her. After the beam passes through the electric fields created by the electrostatic members it may be deflected by pairs of oppositely disposed ele ments and projected on the fluorescent screen formed on the end of the vessel. 10

In order to maintain the intensity of the beam after deflection and to overcome charging of the vessel wall and also to eliminate reflection which might deleteriously affect the indication of the tracing on the screen, the remaining portion of 16 the wall of the vessel is coated with a non-metallic coating, such as colloidal graphite.

A method of forming the coating on the vessel and the necessary apparatus therefor is disclosed and claimed in my copending application, Serial 20 No. 740,877, filed August 22, 1934, and comprises a coating receptacle involving a reservoir containing "Aquadag or colloidal graphite which is connected to an enclosing vessel by a suitable passageway and air under pressure forces the graph- 25 ite material to rise into the vessel to a proper level. The air trapped above the incoming liquid is removed through an outlet pipe and when the desired amount of coating material is injected into the vessel the air supply is removed from the res- 30 ervoir and applied to the outlet pipe. The pressure of air entering the vessel forces the coating liquid to flow back into the reservoir and when all the excess liquid is removed a uniform coating of colloidal graphite adheres to the wall of the vessel. 5 The coating is dried and baked by heating to form a hard and adherent coating on the vessel. This method facilitates the application of the coating and insures a uniform layer of material on the glass wall. Furthermore, the boundary of the 40 coating on the glass wall adjacent the screen is uniformly spaced from the screen so that thecoating does not mask the fluorescent screen material.

Another feature of the invention is the elimi- 45 nation of stray discharges on the wall of the vessel. This is due to the overlapping arrangement of the electrodes so that no electrons can escape toward the wall, to build up electric fields which cause spreading of the beam of rays. 50

Another feature relates to the arrangement of the electrodes so that the beam emanating from the electron source is focussed by a system of ternary electron optical lenses which is produced in the vicinity of the shield and trapping chamber and the ends of the anode and electrostatic member. The potentials applied to these elements set up electric fields which serve to focus the electron stream in the same manner as physical optical lenses focus a beam of light. Further-'- more, the field present at the adjacent ends of the electrostatic members functions as a combination of two lenses to correct distortion in the same sense that two optical lenses are used to correct for spherical aberration.

A more detailed understanding of the invention may be obtained from the following description and drawings:

Fig. 1 shows in cross-section one embodiment of a device made in accordance with this invention and illustrates the detailed arrangement of the various elements;

Fig. 2 illustrates another embodiment of the invention in the form of unitary assemblies of the electrodes which may be inserted in a vessel similar to that shown in Fig. 1;

Fig. 3 shows in cross-section the detailed structure of the electron emitting cathode;

Fig. 4 illustrates one embodiment of the apparatus for performing the operations for applying a coating on the vessel in accordance with a method of this invention; and

Figs. 5 and 5A show another embodiment of the invention in which the electrodes are arranged in two units which cooperate to project a cathode stream to a large screen on the: end of the device.

Referring to Fig. 1, the discharge device in one aspect of this invention, is embodied in an elongated enclosing vessel |ll having an inwardly pro-- jecting stem terminating in a press I2 in which the leading-in wires for some of the electrodes are embedded. This vessel has a long tubular portion I3, an outwardly tapered portion 4 forming an extension of the tubular portion and a dome-shaped window portion I5. A fluorescent coating or screen I 6 is deposited on the inner 1 surface of the window portion. A highly efficient fluorescent coating may be formed on the window portion of the vessel in accordance with the disclosure in U. S. Patent 1,603,284, granted October 19, 1926 to J. B. Johnson. The screen I6 becomes fluorescent upon impact by an electron beam and shows a figure on the screen when the beam is influenced or deflected by circuit under test which gives an indication of the type of curve or variation desired to be shown. The electron beam emanates from a primary source, such as an equipotential cathode or emitter ll, shown more clearly in Fig. 3. This cathode comprises a metallic thimble 8 having an emissive coating l9 on the closed end of thermionically active substances, such as barium and strontium oxides. Within the thimble is an insulating plug 20 having twin bores through which a heater element 2| extends. Between the'end of the plug 20 and the dome of the thimble I8 is a cavity 22 in which the heater element is looped as shown at 23. The terminations of the heater element 2| are twisted together at 24, to prevent a ripple from being introduced into the cathode beam when alternating current is employed as the energizing source for the heater element. The heater element 2| is connected totwo leading-in wires 25 and 26 extending from the press l2, and the thimble I8 is connected to and supported by a conductor 21. The cathode I1 is arranged in the axis of the vessel so that a beam of electrons emanating therefrom is projected to the axis of the fiuorescent screen on the other end of the vessel l0.

The cathode I1 is surrounded by a tubular screen or shield 28, of non-magnetic material, such as aluminum, which is supported from the press |2 by a short wire 29 and a leading-in wire 30. The top of the shield 28 is closed by a disc 3| having a central aperture substantially in alignment with the end of the cathode ll. The disc 3| is attached to the shield 28 and together with the shield form an enclosure for the cathode IT. The enclosure around the cathode facilitates the concentration of the emission of electrons from the cathode since the tubular shield 28 prevents any electrons emitted from the cathode from leaving the confined space within the shield except through the aperture, and "also controls the number of electrons permitted to pass through the aperture 3|, by applying a suitable potential to the leading-in wire 30, and therefore may be used as a modulating electrode or trigger control electrode. It, furthermore, conserves the heat generated by the cathode.

An anode 32 is arranged in the axis of the vessel in alignment with the aperture in the modulating disc 3| and may be in the form of a tubular member. The tubular anode 32 is preferably of non-magnetic material, such as aluminum and is rigidly held in position by a chamber which extends beyond the modulating disc 3|. This chamber has a cup-shaped form and consists of a disc 33 having a central aperture through which the anode 32 extends, so that the anode may be afiixed to the disc by soldering or welding it the inner surface of the disc, and a cylindrical metallic shield or member 34 of similar material which extends downwardly from the disc 33 to a point well beyond the inner end of the shield 28 so that the modulating disc 3| is wholly within the boundary of the metallic member 34 and the shield 28 is reentrant with respect to the member 34. The anode 32 and the cup-shaped enclosure comprising the disc 33 and the cylindrical shield 34 are supported from outwardly extending wires which are held in supporting members, such as glass IOds 35 and 36, which extend from the stem in parallel relation outside the range of the electrodes.

A trapping chamber 31 may be formed intermediate the modulating disc 3| and the anode 32 by two parallel spaced discs 38 and 39, in the form of bafiie plates with central apertures which are arranged in the cylindrical member 34 and are secured to the walls thereof to form an enclosure to entrap any electrons that are not axially projected from the aperture in the primary modulating disc 3|. In order to draw the electrons from the emission source or cathode I! it is necessary to apply a positive potential to the anode structure. For this purpose a leading-in wire 40, projecting through the side of the cylindrical portion |3 of the vessel, is connected to the anode structure adjacent the supporting wire attached to the support 35 and the member 34. The positive potential applied to the trapping chamber and anode 32 causes an electric field to extend within the scope of the discs 38 and 39 and thereby produce, in effect, a primary electron lens for focussing the beam of electrons. an electric field extends into the end of the anode away from the disc 33 and therefore produces a second electron optical lens through which the beam of cathode rays is projected. In effect, the second lens is similar to the first lens, but due to its spacial relation with respect to the emission source, the beamof cathode rays is concentrated into a fine pencil of electrons.

' electrostatic electrode 4|.

An elongated electrostatic focusslng member or electrode 4|, in the form of a metallic cylinder 01' non-magnetic material, such as aluminum, is supported in axial alignment with the preceding electrodes by supportwires extending toward the support rods 35 and 36. This member should be preferably several times the length of the anode and have a diameter substantially the same as the length of the anode. Furthermore, the end nearest the anode should overlap the anode so that the end of the anode is reentrant with respect to the A higher positive potential is applied to this electrode through a leading-in wire 42 which extends from the cylindrical portion of the vessel and is connected to the electrostatic electrode 4| by a support wire extending to the support rod 36. The potential applied to this electrode produces the electric field which extends into the end of the anode 32 and forms the second electron optical lens for focussing the beam of cathode rays projected toward the screen at the other end of the vessel. An additional electric field is produced at the end of this electrode due to the potential applied to the conductive coating on the wall of the vesselwhich will be described hereinafter. This field forms a third electron optical lens to concentrate and focus the stream of electrons and also functions as a correctional lens similar to an optical lens for the correction of spherical aberration. The electrostatic focussing produced by the member 4| insures concentration of the beam of rays which is projected therethrough and the length thereof is closely related to the dimensions of the anode 32. As an example, the anode 32 may be a tube having an internal diameter of I; of an inch and a length of inch, while the inside diameter of the Iocussing tubular member 4| may be inch and the length thereof 3%; inches.

The three-lens system in accordance with this invention insures an optimum concentration of the cathode beam of electrons which is projected along the axis of the vessel toward the screen. Furthermore, the overlapping'assembly of the various electrodes insures that none of the electrons in the beam can be diverted to the glass wall of the vessel and there build up-electric fields which might influence the beam of cathode rays being projected along the axis of the vessel. It is well known that if the glass assumes a negative electric charge electrons in the beam will be repelled, and consequently such charges on the glass wall will seriously affect the concentration of the electron beam emanating from the cathode. Since the cathode is completely shielded by the cylinder 28 and only the aperture in the modulating disc 3| permits a projection of cathode rays and the'area in the vicinity of this disc is completely shielded by the depending edge of the shield 34, it is evident that no electrons can escape from the beam toward the wall of the vessel. In the same manner the travel of the beam through the trapping chamber is completely shielded by the cylindrical wall of the shield 34 and when the beam enters the anode 32 it is completely shielded by the tubular construction of this electrode. Similarly, the path of the beam is protected along the, whole length of the electrostatic electrode 4|, due to its cylindrical form.

and the end of the anode is protected because of its reentrant arrangement with respect to electrostatic member 4|. It will therefore be seen that along the whole path of the beam it is completely shielded from the wall of the vessel so 1 that no electric charges can build up on the wall to influence the cathode beam.

After the beam is projected from the end of the electrostatic focusslng member 4| it must still travel a considerable distance to the screen IS on the end of the vessel and in order to prevent electric charges from building up on the wall portion between the electrode 4| and the screen, this wall is provided with a non-metallic coating or layer 43, of colloidal graphite, commercially known as Aquadag. It will be noted that the coating extends beyond the edge of the electrostatic member 4! so that the end of the member 4| is reentrant with respect to the coating 43. This prevents any charges spreading to the wall of the vessel in the horizontal plane of the end of the member 4!. The graphite coating on the wall of the vessel prevents the building up of electric charges or fields on the glass wall which might influence the beam of rays projected to the screen IS. A leading-in wire 44 is sealed in the wall of the vessel adjacent the coating 43 and is connected thereto to apply a still higher potential to the coating so that the graphite material in the coating forms a conductor for establishing a focussing field at the end of the cylinder 4| for the beam of rays projected toward the screen.

In view of the fact that the conductive coating 43 should not ordinarily flow over the surface of the fluorescent screen l6 it is evident that considerable care must be employed in forming the coating on the inner surface of the vessel wall. An eflicient apparatus for producing this coating in the vessel is shown in Fig. 4 in which the vessel I0 is provided with a removable plug 45 having an inlet tube or connection 46 which extends into the vessel ill a slight distance beyond the inner surface of the plug 45. An elongated outlet tube 47 extends through the plug 45 and terminates within the vessel ill at a point slightly beyond the line to which the coating is desired. The inlet connection 46 is an elongated U-shaped tube which is connected to a reservoir 48 provided with a valve 49 between the reservoir and the inlet tube 46. A similar valve 50 is inserted in the mouth of the reservoir and normally is in a closed condition except when it is desired to replenish the colloidal graphite material 5| within the reservoir. Adjacent the valve 50 and above the level of the colloidal graphite coating material Si is a tubular projection 52 to which may be connected any source of pressure, such as air.

The method of coating the inner wall of the vessel I 0 consists in opening the valve 49 and applying air pressure to the tube 52 to inject air into the reservoir 48 whereby the coating material is forced into the vessel It) through the inlet connection 46. The pressure of air is maintained constant until the level of the coating liquid reaches the level of the dotted line 53 in the vessel It). During the filling of the vessel ID with the colloidal material all of the imprisoned air in the vessel displaced by the liquid is ejected through the outlet pipe 41 and when the level of the coating material reaches the line 53 the air pressure is removed from the out of the end of the vessel II]. It is to be understood that in practice the U-shaped tube is mounted in such a position that the end projecting into the vessel I0 is approximately at the same height as the level of liquid in the reservoir 48 and that the vessel I0 is above the elevation of the reservoir 48. After the coating operation is completed the vessel Ill is dried in an oven and baked to form a hard and adherent coating on the inner wall of the vessel. This methodthe glass and the coating such as might be pres-- ent if a metallic coating is applied to the vessel.

While the beam of cathode rays emanating from the cathode is completely controlled electrostatically to insure a concentrated beam of electrons and the production of a bright and intense spot on the fluorescent screen, this spot being of very small diameter, for instance, one millimeter, it is evident that this beam may be deflected, in any well known manner, to cause the indication of the deflection to be reproduced on the fluorescent screen. For instance, the beam may be deflected electrostatically by two pairs of oppositely disposed plates such as plates 55 and 56 supported by leading-in wires 51 and 58, respectively, which are sealed through the side wall of the vessel III. A similar plate 59 is shown above the plates 55 and 56 and this plate together with a similar parallel plate, not shown, is arranged at right angles to the plates 55 and 58 and provided with suitable terminals and supports through the side wall of the vessel. The vessel I0 is highly evacuated by well known pumping equipment to such a degree that no gas ionization occurs in the vessel to influence the focussing of the beam of electrons or enter into the discharge from the emission source. The vessel is hermetically sealed at 63. after the evacuation is completed.

In the device shown in Fig. 1 the anode structure and the electrostatic element are shown supported from glass standards and the deflecting plates are supported from wires extending through the wall of the vessel. It is evident that this invention may also be embodied in a structure in which the leading-in wires are contained in the stem of the vessel so that all the electrodes may be mounted as a unit on the stem and the unit inserted in the vessel without the need of any other connections through the wall of the vessel. Such a structure is shown in Fig. 2 in which a stem I having a press l2 surrounding leading-in wires 25 and 25 for the heater element 24 and a leading-in wire 21 for the emission source or cathode IT. The cathode is surrounded by a cylindrical shield 28 attached to the press by wire 28 and leading-in wire 38. The shield 28 is provided with amodulating disc 3| similar to the disc shown in Fig. 1. A pair of collars BI and 62 embrace the stem II and carry support rods 53 and 64 which are attached to the shield member 34 in which the trapping plates 38 and 39 are situated. The top of the shield 34 is closed by the disc 33 which has a central aperture for the reception of the tubular anode 32. Surrounding the periphery of the disc 33 is an insulating ring or collar 65 having an overhanging edge extending beyond the edge of the disc 33 to readily position the insulator with respect to the rest of the electrode structure. The'insulating collar may be secured in position by cement 66 which fills the space between the wall of the shield 34 and the edge of the insulating collar 65. The insulating collar supports two standards or rods 81 and 58 which are connected to the elongated focussing member 4|. The member 4| is provided at its upper edge with an outwardly projecting flange 69 which forms a base for an insulating ring 10 secured to the flange 58 by cement 'II. The ring 18 carries a short cylindrical metallic member 12 which is provided with a conductor I3 extending to the stem. This member and the potential applied to it forms the fleld for focussing the electron stream at the end of the electrostatic focussing member 4|. The short cylinder 12 carries an insulating collar 14 in which are positioned supports 15 and 18 for the parallel deflecting plates 11 and I8 and also other supports for the second pair of deflecting plates, only one of which is shown at 19 and connected to a support 88 extending into the insulating ring 14.

anode assembly and this leading-in wire is embedded in a seal between the stem flare and the vessel wall in a manner well known in the art. A leading-in wire 82 embedded in a seal oppositely disposed with respect to the leading-in wire 8| extends through an insulating glass tubing 83 and is connected to the support 88 so that a suitable potential may be impressed on the electrostatic focussing member 4|. Suitable leading-in wires 84 and 85 extend through the press l2 and are located in an insulating tubing 86 and separately connected to the supports 15 and 88 of the deflecting plates 11 and 19, respectively. On the opposite end of the press leadingin wires 81 and 88 extend through an insulating tube 89 and the conductor 81 is connected to the support wire 16 of the plate 18. It is understood that the conductor 88 is connected to the other deflecting plate which is arranged parallel to the plate I8 shown in Fig. 2. This arrangement forms a compact and unitary assembly in which all the electrodes are rigidly held in axial relation so that the beam of rays emanating from the cathode is maintained in the axis of the various electrodes.

The device shown in Figs. 5 and 5A is a large embodiment of the invention in which the stream of electrons is projected for .a distance of about 3 feet and the diameter of the fluorescent screen is approximately 15 inches. It is evident that in order for the beam to travel this distance it must be focussed accurately to maintain the intensity of the beam when it reaches the screen. The device consists of a vessel having a cylindrical portion I8 connected to an outwardly tapered portion .H which continues up to the domeshaped window portion IS on which the screen I5 is deposited. The cylindrical portion of the vessel III is provided with a reentrant tubular portion 88 which is open at its inner end and provided with an outwardly extending long tubular portion 8|. The outer end of the long tubular portion 8| is provided with a reentrant stem 92 which terminates in a press portion 93. The press supports leading-in wires 94 and 95 for the inand a conductor attached to the cathode is sealed in the press at 91. A hollow cup-shaped der I05 or highly purified material, such as magnesium silicate or isolantite". The insulating cylinder forms a support for the anode assembly and the elongated focussing electrode and rigidly maintains the space relation of these elements.

-' The anode structure consists of a. single piece of metal having a cup portion I06 and a shorttu- .bular portion I07 at the top of the cup portion.

The interior surface of the cup portion is stepped to insure accurate spacing between perforated discs or baflie plates I08 and I09 and to provide chambers of definite areas on opposite sides of these plates. The anode structure is held within the insulating cylinder by a locking screw, .not shown. A voltage is supplied to the anode structure by a leading-in wire IIO which is sealed in the side of the stem 92 and connected to the upright support I03, the support carrying a short stub wire I II which is attached to the edge of the anode structure. An elongated focussing electrode H2 is provided at its lower end with a reinforcing collar which is threaded to receive screws which pass through the cylindrical insulator I05 to hold it rigidly in position. It will be noted from this assembly that the cathode is completely enclosed by the shield electrode 98 and this electrode is reentrant with respect to the cup portion of the anode structure and the anode to! is reentrant with respect to the focussing electrode M2.

A second electrode unit is supported from the stem 90 by a structure including clamping bands II t, II5 which embrace the stem and carry support rods H5 and Iii. These rods are attached to an insulating disc H8 having a central hole in Y which is situated a metallic cylinder M9. The

metallic cylinder I I9 is held on the disc M8 by a flanged rim I2t and is concentric with and partially surrounds the end of the elongated focussing member 2. A pair of rods I2I and I22 project upwardly from the disc H8 and carry a pair of parallel plates, only one of which is shown at I23. A similar pair of rods, I24 and I25, of longer length, extend from the disc 8 and 'carry a pair of parallel plates I26 and I21 which are arranged at right angles to the plane of the plate I23. A graphite coating I28 is formed on the wall of the tube from a point I29 up to the screen I6 and an electrical connection is made with thiscoating by a leading-in wire I30 sealed in an arm NH. The voltage applied to the metallic coating on the wall of the vessel is also applied "to the cylindrical metallic electrode H9 by a helical expansion spring I32 which presses against the metallic coating on the wall of the vessel and is attached to a conductor I33 which passes through the insulating disc and is attached to the side wall of the cylindrical electrode H9. The four deflecting plates are provided with suitable terminal wires which are sealed in the top of thestem 90 and pass out of the vessel between the cylindrical portion I and the long electric fleld produced in the vicinity of the cylindrical electrode H9 and the top ot the 0- cussing electrode II2 forms a iocussing lens for- 1. A cathode ray discharge device comprising a highly evacuated vessel having a fluorescent screen at one end thereof, an electron emitter at the otherend thereof, a ternary electron optical lens system between said emitter and said screen, and a non-metallic conductive coating on said vessel between said lens system and said screen.

2. A cathode ray discharge device comprising a highly evacuated vessel having a fluorescent screen at one end thereof, an electron emitter at the other end thereof, a ternary electron optical lens system between said emitter and said screen, and a colloidal graphite layer on the wall of said vessel, said layer being uniform and continuous from said screen to said lens system.

3. A cathode'ray discharge device comprising a highly evacuated vessel having a stem at one end, a fluorescent screen at the other end, an electron emitter supported on said stem, a shield surrounding said emitter and having an apertured closure at one end, an inverted cup-shaped member superimposed on said shield, a tubular anode projecting from the axis of said member, spaced parallel bafiie members situated in said member and having apertures in alignment with said anode, and an elongated electrostatic tubular member adjacent said anode.

4. A cathode ray discharge device comprising a highly evacuated vessel having a stem at one end and a screen at the other end, a conductive coat ing on the wall of said vessel, an electron emitter supported by said stem, a primary iocussing member, a secondary focussing member, and an elongated focussing member, each of said members and said coating successively surrounding a beam of rays to be projected from said emitter to said screen.

5. A cathode ray discharge device comprising a highly evacuated vessel having a stem, an electron emitter supported by said stem, a primary focussing member, a secondary focussing member, an elongated focussing member, said members successively overlapping the adjacent boundary of the preceding member, and a graphite fllm on the wall of said vessel having a portion overlapping said elongated focussing member.

6. A cathode ray device comprising a highly evacuated vessel having a fluorescent screen at one end, a cathode at the other end for projecting a beam of rays toward said screen, and a series of electrostatic focussing members intermediate said screen and cathode and arranged to eliminate dispersion of said rays to the wall of said vessel throughout the length of said vessel, said members including a primary focussing member, an electron trapping member, an anode, a distortion correcting member, and a terminating member, said primary member, anode and correcting member each having a portion extending within the boundary of the succeeding member.

7. A cathode ray device comprising a highly portion, an outwardly tapered portion and a terminating wall portion, a fluorescent screen on said terminating wall portion, a non-metallic coating on said tapered portion, and a unitary electrode assembly on said stem supported within said cylindrical portion, said electrode assembly including a cathode, a cupshaped shield member surrounding said cathode, a cup-shaped electron trapping member superimposed on said shield member, a tubular anode supported by said trapping member in alignment with said cathode, and an elongated iocussing member surrounding a portion of said anode and coaxially related therewith.

8. A cathode ray discharge device comprising a highly evacuated vessel having a fluorescent evacuated vessel having a stem, a cylindrical screen at one end and a stem at the other end, and a unitary electrode structure supported by said stem, said structure comprising an electron emitter, a shield having an aperture surrounding said emitter, a cup-shaped member partially surrounding said shield and supported from said stem, a tubular anode supported by, said member, an elongated tubular focussing member insulatingly supported by said cup-shaped member and partially surrounding said anode, a cylindrical metallic member insulatingly supported by said tubular focussing member, an insulator attached to said cylindrical member, and a plurality of deflecting plates carried by said insu- I

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