US2779893A - Device comprising an electric discharge tube having a concentrated electron beam - Google Patents

Description

Jan. 29, 1957 J. L. H. JONKER 2,779,893

DEVICE COMPRISING AN ELECTRIC DISCHARGE TUBE HAVING A CONCENTRATED ELECTRON BEAM Filed June 30, 1951 INVENTOR JO H AN LODEWIJK HENDRIKJONKER BY%M AG EN United States Patent DEVICE COMPRISING AN ELECTRIC DISCHARGE TUXE HAVING A CONCENTRATED ELECTRON BE M Johan Lodewijk Hendrik Jonker, Eindhoven, Netherlands,

assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee This invention relates to a device comprising an electron discharge tube having a concentrated electron beam through the use of which a very high mutual conductance can be developed in a simple manner.

It has previously been suggested to increase the sensitivity of deflection control of a tube by means of a space charge developed between the beam and the deflection electrode, the deflection due to the deflection electrode being assisted by the space charge. Such an increase was attained by making improvements in the deflection control itself in a tube having a double control. In addition, it has been found possible to utilise the influence of space charge to ensure a very high mutual conductance even in the case of intensity control, if the electron beam is directed upon any of the collecting electrodes only as a result of space charges formed by the beam current itself in accordance with the intensity of the beam. The deflection of the electron beam due to these space charges, which was formerly found to be generally undesirable is now used to direct a portion of the beam away from a given collecting electrode and into a further collecting electrode. The last-mentioned collecting-electrode forms in general the anode. The intensity of the beam is controlled by the control electrode so that increasing beam intensity increases the intensity of that portion of the beam directed upon the collecting anode referred to. In addition, simultaneously, with this increase in beam intensity a large portion of the beam is directed upon this electrode. The beam thus can be fully deflected in accordance with the controlled intensity of the beam without a separate deflection control.

A greatly preferred embodiment for realising the abovedescribed principle is obtained through the use of a device comprising an electric discharge tube having a concentrated electron beam and an electrode system comprising at least a cathode, a control grid and two collecting electrodes, in which the electrons are directed upon any one of the collecting electrodes only by reason of charges which are formed by the beam itself in accordance with the intensity control of the beam current, the electron beam being deflected, in accordance with the invention, by a deflecting or reflecting electrode maintained at zero or fixed low potential. This deflection electrode establishes a deflection field whose curvature increases with an increase of the beam intensity due to the presence of space charge. In the case of sufliciently high beam intensity, the deflection field is distorted so that a portion of the beam is directed upon a further collecting electrode. The deflecting electrode may be shaped in the form of an electron mirror the reflection angle of which is varied by space charges.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, in which Figs. 1, 2 and 3 show diagrammatically embodiments of tubes suitable for use in device according to the invention, and

Fig. 4 shows the Ia-Vg characteristic curve of such tubes.

Referring to Figs. 1 to 3, the cathode is designated 1, the intensity control electrode 2 and a screen grid 3. The control electrode 2 may comprise small screens so that the electron flow is concentrated to form a beam, but, as an alternative, separate beam-forming electrodes may be arranged.

Referring to Fig. 1, a beam is directed by a deflecting or reflecting electrode 13 maintained at a fixed zero or negative potential to a grid-shaped collecting electrode 14. At an increasing current strength a space charge is produced due to which the electrons are deflected to a greater extent and reach the anode 15. The formation of the space charge may be assisted by the arrangement of small rods or strips 16 maintained at low or zero potential. An alternative form of this construction is shown in Fig. 2 in which the collecting electrode 15 is replaced by a secondary emission auxiliary cathode 17. The collecting electrode 14 is replaced by a collecting electrode 18 which in this case may be plate-shaped, an output anode 19 maintained at a high positive potential being arranged adjacent the curvature center of the deflecting electrode 13 and being struck by the secondary electrons of the auxiliary cathode 17.

Referring to Fig. 3 the deflecting electrode 22 is formed and connected to ground such that it acts as an electron mirror and the beam is completely reflected upon the collecting electrode 20 when the beam is of low intensity. When the beam intensity is high the beam is directed upon the anode 21, as a result of field distortion due to the'occurrence of a space charge in the beam.

Fig. 4 shows the IaVg characteristic curve of a normal tube which has only intensity control without the use of space charge deflection (curve 1). Curve II is the IaVg characteristic curve of a similar tube in which space charge deflection is used. It clearly shows the intense increase in mutual conductance, the advantage being that the latter is obtainable without very accurate electrode machining or very small electrode spacings.

Obviously, still further embodiments are possible Without departing from the scope of the invention.

What I claim is:

l. A circuit arrangement comprising an electric discharge tube having a cathode, a control grid and a screen grid for producing a concentrated beam of electrons in a given path, a cylindrical reflecting electrode surrounding said screen grid with the axis of said reflecting electrode displaced from the axis of said screen grid so that said beam of electrons is directed substantially perpendicularly to a radius of said reflecting electrode which radius passes through the axis of said screen grid; an output anode located substantially coaxially within said reflecting electrode, a source of potential connected to said output anode to make it positive with respect to said reflecting electrode, whereby said beam of electrons is deflected in a curved path around said anode; a first collecting electrode located within said reflecting electrode on the opposite sides of said anode from said screen grid; a source of potential connected to said output electrode, said source having a value intermediate the value of potential connected to said anode and the potential of said reflecting electrode, said collecting electrode being located to intercept the electrons of said beam when the intensity of said beam is relatively low; a second collecting electrode located within said reflecting electrode and on the opposite side of said anode from said screen grid, said second collecting electrode being closer to said anode than said first collecting electrode whereby said beam of electrons impinges on said second collecting electrode when the intensity of said beam is relatively high, said second collecting electrode being electrically connected to said first collecting electrode to operate at the same potential;

a secondary emissive b'ati'ng 'ori' the side of'saidsecoiid ofp'rimary' electrons in said b'earn striking said second.

collecting electrode, said second collecting electrode being located to direct said. secondary electrons to said anode; an input circuit connected to said control grid to control the intensity of said beam; and an output circuit connected to said anode to derive therefrom an output signal.

2. A circuit arrangement as set f0rth.inclaim 1 wherein the reflecting electrode is maintained at ground potential.

References Cited in the file of this patent UNITED STATES PATENTS Skellett Aug. 18, Thompson Aug. 18, Wagner Aug; 18, .Sk'ellett Jime 18, Miller Jan. 9, Hosernann Jan. 23, Clark Octr9, Sziklai Dec. 4, Wallmark Dec. 6,

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