US 3304461 A
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D. W. PRINE Feb. 14, 1967 SUPPORT FOR ELONGATED ELECTRODES OF ELECTRON BEAM TUBE Filed Sept. 20, 1963 1N VENTZOR.
Den/1d W Przrze United States Patent Ofifice Patented Feb. 14, 1967 3,304,461 SUPPORT FOR ELON-GATED ELECTRODES F ELECTRON BEAM TUBE David W. Prine, Maywood, Ill, assignor to Zenith Radio Corporation, Chicago, 111., a corporation of Delaware Filed Sept. 20, 1963, Ser. No. 310,269 4 Claims. (Cl. 315-3) The present invention relates to electron beam devices. More particularly, it pertains to ruggedized structural assemblies useful in the manufacture of high-frequency electron beam devices such as parametric amplifiers.
Electron beam devices often are enclosed by an envelope of glass with the various electrical connections being made by means of wires which project through the envelope walls. Such devices also have been constructed with envelopes of ceramic material. A particularly attractive approach for ruggedness utilizes an envelope composed of a plurality of sleeves of ceramic material joined together by annular metal elements which serve as electrical connectors to internally disposed electrodes. The well-known lighthouse tubes are an example of such construction.
In certain high frequency electron beam devices, it has been customary to utilize envelopes composed of ceramic sleeve sections and, in a manner similar to that employed in lighthouse tubes, with the various sections separated by annular metallic shields. The electrodes within the different sections of the device may be suspended fr-om the internal sleeve walls by conductive pins which project through and are sealed to the ceramic material. However, such seals are fragile and diificult to make. Further, the pins or wires exhibit substantial inductance which leads to undesirable self-resonance with the associated interelectrode capacitance. Further, the pins or wires often become corroded in the firing process necessary to satisfactorily evacuate the device; consequently, they become what are known as lossy inductors. Because of the fragile nature of the seals, it is extremely difiicult to clean such corroded materials.
The foregoing problems arise particularly in the case of high-frequency electron beam parametric amplifiers utilizing broad band coupler and quadrupole sections. One solution to the aforementioned corrosion difiiculties has been to make the quadrupole itself of a lossy material for the purpose of loading and effectively broadening the tuning of the quadrupole. However, the magnitude of such intentional losses is difiicult to control accurately and leads to nonuniformity from tube to tube. Other solutions to the problems thus far suggested raise either electrical or mechanical difficulties.
There are a number of other difficulties connected with the manufacture of such devices. In the electron beam parametric amplifier particularly, it is necessary to align the various electrodes accurately. The phase relationship between the diiierent electrodes of quadrupole pump structures must be precisely established. It is highly desirable that the connections to external circuitry be easily made, that such circuitry, particularly in connection with coupling efficiency, phase balance and the number of circuit elements, be simplified and minimized and, in general, that the overall tube construction be facilitated.
It is therefore a general object of the present invention to provide an electron beam device of rugged construction and which avoids the aforenoted difiiculties and deficiencies of prior devices.
It is another object of the present invention to provide an electron beam device in which the alignment of the parts during manufacture is facilitated.
A further object of the present invention is to provide an electron beam device in which it is comparatively till simple to establish and maintain phase relationships between diiferent ones of the internal electrodes.
Still another object of the present invention is to provide an electron beam device of the above character and in which the interelectrode capacitance is minimized.
The invention resides in an electrode and envelope assembly for an electron beam device in which the beam is projected through an extended space. First and second conductive washers are disposed individually across respective opposite ends of a sleeve of insulating material. Each of the washers has a circumferentially-limited portion or ear projecting outwardly from the external surface of the sleeve and the opening in the washer defining a finger projecting radially inward part way to the tube axis, with the washers being mutually oriented to dispose the fingers in angularly spaced relative positions. Disposed inside and generally parallel with the sleeve is a pair of elongated electrodes. The electrodes are each conductively secured at one end to an inner end of a respective one of the fingers and each projects as a cantilever member in the direction of the other of the washers. The electrodes together in correspondence with the selected angular positions of the washers define, across the tube axis, a transverse field region.
The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The organization and manner of opera tion of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawing, and in which:
FIGURE 1 is a perspective view, partially broken away, of an electron beam device embodying the present invention;
FIGURE 2 is a cross-sectional view taken along line 22 in FIGURE 1;
FIGURE 3 is a fra mentary cross-sectional view taken along line 3-3 in FIGURE 2;
FIGURE 4 is an elevational view of an element utilized in the device shown in FIGURE 1;
FIGURE 5 is a cross-sectional view taken along line 55 in FIGURE 1;
FIGURE 6 is a fragmentary cross-sectional view taken along line 6-6 in FIGURE 5;
FIGURE 7 is a schematic diagram of an equivalent circuit of a portion of the device shown in FIGURE 1;
FIGURE 3 is a diagrammatic view of an element utilized in analyzing the electrical characteristics of a portion of the device shown in FIGURE 1; and
FIGURE 9 is a diagram of further utility in analyzing the electrical characteristics of the aforesaid portion.
In the device shown in FIGURE 1 for purposes of illustrating the present invention, an envelope 10 is composed of a plurality of sleeves or sleeve sections 11-22. All have the same internal and external diameters and are disposed coaxially in end-to-end relationship to define a hollow cylinder in which the various electrodes of an electron beam parametric amplifier of the quadrupole type are disposed. Sandwiched individually between the successive sleeve sections are a plurality of washers 23- 35. The washers are metallic and the sleeves are of a high-dielectric-constant ceramic material. The extreme outer ends of the resultant cylindrical assembly are closed by caps 36 and 37, with cap '36 being metallic and including in known manner an exhaust tubulatio-n 38.
During final assembly of device 10, the surfaces to be joined between the sleeves and washers are coated with a soldering frit material after which pressure is applied on the outer faces of caps 36 and 37 and the entire assembly is baked at a high temperature to form an air-tight envelope. The techniques and materials for forming such ceramic-to-metal seals are conventional and well-known. Similarly, in known manner, the completion of the processing involves baking the device at a high temperature while it is evacuated by means of a pump coupled to tubulation 38. When the pressure is sufiiciently low, tubulation 38 is closed.
In the finished device, washers 23-24 are annular in form with washers 23 supporting the cathode and heater elements and washers 24 having centrally disposed apertures of varying sizes to serve as the focusing assembly of an electron gun 40 from which the electrons are projected along a path corresponding to the longitudinal axis of device 10. The details of electron gun 40 form no part of the present invention and therefore need not be described further. A suitable gun is disclosed and claimed in U.S. Patent 2,997,615 issued August 22, 1961 to Robert Adler.
Included in device are three principal sections composed of an input coupler 41, a quadrupole pump section 42, and an output coupler 43. Shield washers 25, 28, 31 and 34 separate those sections one from another and from the electron gun collector. Each shield is simply an annulus having a small aperture on the tube axis through which the electron beam passes. Washer 35 adjacent end cap 37 is a solid disc of metallic material and serves as the final collector for the electron beam. In the present instance, input and output couplers 41, 43 are of the form known as Cuccia-couplers, each of which includes a pair of deflector plates 45, 46 aligned parallel to and disposed individually on opposite sides of the electron beam path. Quadrupole 42 includes four rods 47-50 aligned parallel to the electron beam and symmetrically disposed circumferentially around the beam path.
The detailed manner of operation of device 10, and particularly of the input and output couplers and the quadrupole pump, do not form a part of the present invention, per se, and therefore reference is made for a fuller understanding to an article entitled The Quadrupole Amplifier, A Low-Noise Parametric Device by Adler et al. at pages 1713 through 1723 of the Proceedings of the I.R.E. for October 1959. That subject matter is also described, together with numerous variations and improvements, in British patent specification 929,015 published June 19, 1963. Briefly, input signal energy to be amplified is -fed to input coupler 41. Quadrupole 42 is coupled to a source of pumping potential as a result of which a quadrupole-shaped field subjects the electrons to periodic forces of a character to parametrically amplify the electron signal motion imparted to the electrons in coupler 41. Output coupler 43 extracts the amplified signal energy and feeds it t-o a load.
As constructed in accordance with the invention, the internally disposed elongated electrodes are electrically connected by and aifixed for support to the pair of conducti-ve washers disposed individually across respective opposite ends of the enveloping sleeve section. Each of the washers has an internal opening defining an inwardly projecting finger to the inner end of which an individual one of the electrodes is conductively secured. The respective washers are mutually oriented to dispose the fingers, and hence the electrodes, in angularly spaced relative positions. FIGURES 5 and 6 depict the details of input coupler 41; output coupler 43 is identical. Washers 26 and 27 are disposed across the opposite ends of sleeve 14. Washer 26 has an internal opening 52 which defines an inwardly projecting finger 53 to the inner end of which electrode 45 is conductively secured. Similarly, electrode 46 is afiixed to the inner end of a finger 54 defined by a central opening in washer 27. The washers are mutually oriented to dispose fingers 53 and 54 oppositely. For added rigidity, electrode 45 is secured on its backside to the inner surface of washer 2 6 by a strut 56 in the form of a web-shaped plate. In the same way, electrode 4-6 is rigidly supported from washer 27 by a strut or web 57.
As shown, washers 2-6 and 27 have approximately the same internal and external diameters as the adjoining ceramic sleeve sections but each include a portion extending beyond the exterior surface of the sleeve which serves as a feedpoint for the coupler and for which purpose an electrical lead can be attached. This connection point preferably takes the form of a laterally extending car 53 on washer 26. The other feedpoint is by way of an car 59 on washer 27. While not shown in the drawings for simplicity of viewing, each of the electron gun shield and collector 'washers may have a similar ear for the purpose of making electrical connection.
A modified form of the construction just discussed finds special utility as applied to the support of the quadrupole electrodes. To that end, washers 29 and 30, each disposed individually across respective opposite ends of sleeve 17, have an internal opening 62 which defines a pair of oppositely disposed inwardly projecting fingers 63-64 and 65-66, respectively. Quadrupole electrodes 47-50 are conductively secured individually to the respective inner ends of fingers 63, 66, 64, and 65. Washers 29 and 30 are mutually oriented to dispose the respective finger pairs at angularly spaced relative positions.
Further rigidity of the entire quadrupole assembly may be had by employing straps or webs in a manner similar to that illustrated in FIGURE 6 with respect to the input coupler. In addition, the mechanical stability is preferably enhanced by making quadrupole rods 47-50 hollow, as shown. As in the case of the input coupler construction, washers 29 and 30 have approximately the same diameter as the adjoining sleeve sections but are provided with a portion, such as respective cars 68 and 69, to which pump supply leads are affixed in operation.
Further in accordance with the invention, the different sections are assigned dimensions and spacings which minimize the external capacity. FIGURE 7 depicts an equivalent circuit for the quadrupole assembly shown in FIGURE 3. In parallel between feedpoints 68, 69 is the capacitance C between washers 29 and 30 and the capacitance C of the four quadrupole rods 47-50. In series between the opposite ends of those equivalent capacitors and ground are the respective capacities C between each washer and its adjacent shield.
Typical ceramic materials utilized in electron device applications have a dielectric constant of the order of 9.0. In View of this comparatively high constant, the primarily significant portion of the resulting electric field is confined within the ceramic wall. Consequently, it is permissible to simplify calculations by considering the external capacitance to result from the equivalent structure of four parallel fiat rings 70, one of which is depicted in FIGURE 8. The four rings are schematically depicted in FIGURE 9 and in the calculations are substituted for the actual shields and washers. This correspondence is depicted by denoting the equivalent rings in FIGURE 9 with primed numerals which correspond to the elements depicted in FIGURE 3. Consequently, FIGURE 9 indicates the position and spacings of rings or washers 28, 29, 30 and 31'. The inner and outer diameters D and D respectively, corresponds to the inner and outer diameter of the ceramic sleeve sections. The area of each ring 70 may be computed from the equation:
The external capacity C may be determined from the relationship:
where E is the relative dielectric constant of the ceramic, A is the ring area, 6 is the distance between each washer and its adjacent shield, and 5 is the distance between the washers. An examination of the above equation for the external capacitance will reveal that to minimize the capacitance the spacings must satisfy the relationship 5 =26 from which, 6 =L/2 and 6 =L/4, where L is the overall distance between the shields bounding the quadrupole assembly. In a typical construction, utilizing a ceramic having a dielectric constant of 9.0, with the inner and outer diameters of the sections being 0.260 and 0.375 inch, respectively, and with L being equal to 0.624 inch, the external capacity theoretically would equal about 0.662 micrornicrofarads. In actual practice, approximately 10 percent additional capacitance will be encountered due to the effect of portions outside of the ceramic material.
A quadrupole assembly designed in accordance with the invention is capable of operation over a substantial range of frequencies. This arises because of the elimination of lossy inductive structures and by the use of wide fiat signal-conductive portions which minimize series inductance. Further, the phase relationships between the different electrodes are accurately determinable and maintained; it will be noted that the feedpoints 68 and 69 of the quadrupole electrodes are chosen so that the path lengths to each pair of rods fed from a common washer are equal. Consequently, opposite rods are forced to be in phase. The quadrupole rods, therefore, are fully electrically strapped and only two external connections are necessary. It is extremely simple to anti-resonate the quadrupole by merely attaching a loop between the two feed points. An an example of the simplicity of external feed arrangements, the pump source may be transformed through a balun transformer and tapped directly onto the single loop between the feedpoints in order to produce correct impedance match. Additionally, broadening of the bandwidth is easily obtained by simple resistive loading between the feedpoints external of the device.
A significant advantage in construction is obtained through the use of ears 58, 59 and 68, 69. In fabricating the tube, the individual sections are first preassembled by welding the electrodes individually to their respective washers while the components are accurately positioned Within a jig. The ceramic sleeve sections are accurately machined to have parallel surfaces, after which all elements are assembled together in a jig adapted to receive the entire device. The position of each of cars 58, 59 and 68, 69 is selected accurately during the preforming processes to correspond to a fixed angular rotational orientation with respect to the affixed electrode. Su-bsequently, the ears are utilized in association with the accompanying final-assembly jig as index tabs so that all parts are precisely located in rotational position with respect to one another.
The resulting device contains fewer parts than heretofore, an advantage significant in itself considering the large number of different elements involved. While the finalized device is extremely rugged, it lends itself admirably to utilization at extremely high frequencies where the dimensioning of the various parts may involve quite small spacings and element sizes. An noted, such spacings preferably are selected so as to minimize the external capacity. Further, improved performance is obtained because the capacity is not lumped on the end of a series inductance, as in the case of a device in which the electrodes are secured through the ceramic walls by pins. In consequence, an external tuning loop can form a simple resonant circuit with a pure capacitance instead of with a series LC circuit.
While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.
1. In an electron beam device in which the electron beam is projected through an extended space, an electrode and envelope assembly comprising:
a sleeve of insulating material defining an axis therethrough;
5 first and second conductive washers disposed individually across respective opposite ends of said sleeve, each of said washers having a circumferentially limited portion projecting outwardly from the external surface of said sleeve and the opening in the washer defining a finger projecting radially inward part way to said axis and with said washers being mutually rotatable about said axis upon assembly with said sleeve to dispose said fingers in selected angularly spaced fixed relative positions;
and a pair of elongated electrodes, disposed inside and generally parallel with said sleeve, each conductively secured at one end to an inner end of a respective one of said fingers and each projecting as a cantilever member in the direction of the other of said washers and said electrodes together in correspondence with said selected positions defining across said axis a transverse field region.
2. In an electron beam device in which the electron beam is projected through an extended space, an electrode and envelope assembly comprising:
a sleeve of insulating material defining an axis therethrough; first and second conductive washers disposed individually across respective opposite ends of said sleeve, each of said washers having an ear projecting outwardly from the external surface of said sleeve and the opening in the washer defining a finger projecting inwardly toward said axis having a fixed angular orientation relative to said ear and with said washers being mutually rotatable about said axis upon assembly with said sleeve to dispose said fingers in selected angularly spaced fixed relative positions;
and a pair of elongated electrodes, disposed inside and generally parallel with said sleeve, conductively secured individually to the respective inner ends of said fingers and together in correspondence with said selected positions defining across said axis a transverse field region.
3. In an electron beam device in which the electron beam is projected through an extended space, an electrode and envelope assembly comprising:
a sleeve of insulating material defining an axis therethrough;
first and second conductive washers disposed individually across respective opposite ends of said sleeve, each of said washers having an ear projecting outwardly from the external surface of said sleeve and the opening in the washer defining a pair of oppositely disposed fingers each projecting radially inward part way to said axis and having a fixed angular orientation relative to said ear and with said washers being mutually rotatable about said axis upon assembly with said sleeve to dispose said finger pairs in selected angularly spaced fixed relative positions; and four elongated electrodes, disposed inside and generally parallel with said sleeve, each conductively secured at one end to an inner end of a respective one of said fingers of one of said Washers and each projecting as a cantilever member in the direction of the other of said washers and said electrodes together in correspondence with said selected positions defining across said axis a transverse quadrupole-field region.
4. In an electron beam device in which the electron 70 beam is projected through an extended space, an electrode and envelope assembly comprising:
three coaxially aligned insulating sleeves, the two outer sleeves each having a length 6 and the intermediate sleeve having a length 6 said sleeve defining an axis therethrough;
first and second conductive washers individually disposed across the respective outer ends of said outer sleeves and each having a centrally disposed aperture;
third and fourth conductive washers sandwiched individually between the respective ends of said intermediate sleeve and the respective adjacent ends of said outer sleeves, each of said third and fourth washers having an internal opening defining a finger projecting radially inward part way to said axis and with said washers mutually oriented to dispose said fingers in angularly spaced relative positions;
and a pair of elongated electrodes, disposed inside and generally parallel with said sleeve, conductively secured at one end to an inner end of a respective one of said fingers and each projecting as a cantilever member in the direction of the other of said washers,
i the lengths of said sleeves being in accordance with the relationship:
where L is the total distance between said first and second washers.
References Cited by the Examiner UNITED STATES PATENTS DAVID J. GALVIN, Primary Examiner.