US2803780A - Targets for storage tubes - Google Patents

Description

Aug. 20, 1957 .c. DUFOUR 2,80

TARGETS FOR STORAGE .TUBES Filed April I2, 1955 Reading gun Horizontal Vertical deflect/on Fig .1.

Vertical deflectmn.

United States Patent 2,803,780 TARGETS FOR STORAGE TUBES Charles Dufour, Paris, France, assignor to Compagnie Generale de Telegraphic Sans Fil, a corporation of France Application April 12, 1955, Serial No. 500,950 Claims priority, application France April 15, 1954 6 Claims. (Cl. 315--12) This invention relates to targets for storage tubes.

In such tubes, a beam of electrons emitted by a gun known as a writing gun accumulates charges on a target. The writing beam intensity is modulated by an input signal to produce on the target a charge pattern which is an electrical image of the input signal. The beam of electrons emitted by a gun known as a freading gun performs a reading scanning while removing at least a partof the accumulated charges, which provides the output signal of the tube.

The invention more particularly concerns targets for storage tubes of the sometimes known as monolinear scan storage tubes and in which the writing and reading beams scan a single line on the target, especially a circular one, the writing and reading guns being located on either side of the target which accordingly is called a double-sided target since it has two sides respectively facing the writing and the reading space of the tube.

According to the present invention the double-sided target is in the form of a ring consisting of a central conductive core having at least a portion of its surface covered with similar thin strips partly overlapping each other in a uniform way, said portion being symmetrical with respect to two planes of symmetry of said core perpendicular to each other, said strips comprising an insulating layer whose external surface parallel to the surface of said ring is metallized. These strips together with the conductive core form elementary condensers each capable of carrying its own electrical charge, each constituting a point of the target and carrying a charge independent of that of neighboring points.

According to a preferred arrangement, said central core is of aluminum and the strips used are either of aluminum covered on one side with alumina by an anode oxidization process, or of mica metallized in vacuo on one side, the deposited metal being, for example, gold or aluminum.

The invention will be better understood from the following description and appended drawing given solely by way of non limitative example. In the drawing, where similar reference numbers designate similar elements;

Fig. 1 is a diagrammatic view in longitudinal section of a tube provided with a target in accordance with the invention;

' Fig. 2 is a partial sectional view of the upper portion of the target, the section being taken along a plane comprising the axis of revolution of the target;

Fig. 3 is an enlarged view of the overlapping strips on core 8 forming a part of the target. The correct curvature of the strips shown has been indicated.

The tube shown in Fig. 1 comprises a writing gun I and a reading gun Z'centered on the X'X axis. These guns comprise respectively central electrodes 3 and 4. Electrode 3 is driven by the input signal See, through a resistance- capacity network 19, 20. The writing and reading guns are of a known type, and accordingly need not be described in detail, and it will be assumed that denser having the electrodes composing them are subjected to appro priate direct current voltages supplied by sources, not shown.

Both writing and reading beams 5 and 6 perform a circular scanning of the target 7, this being performed by means of horizontal and vertical deflection systems of a known type.. The target 7 comprises a core 8 which is a toroidal solid of revolution about axis X'X. An enlarged section of'this solid in a plane comprising the axis X'X is shown in Fig. 2; the central core 8 is made of aluminum in the example described and has a thickness of the order of 20 mm. The inner surface of the core 8 is covered with strips 9 a few microns thick and l to 2 mm. wide, for example of mica. The outer surface 10 of the strips 9, parallel to the surface of the core is covered with aluminum or gold by metallization. Strips 9 cover the central core and are regularly distributed on the annular target and partly overlap each other. The core has in section two substantially flat sides and two curved sides. Each strip forms with its insulating layer, its metallization and the central core an elementary cona capacity in the order of a picofarad and the operation of which will be described later.

' In Fig. 3, one of the plane portions, i. e. portions covering the fiat sides of the lower portion of the core 8, of strips 9 has been shown. As may be seen, two adjacent strips 9 overlap each other over a distance d of the order of half a millimeter. Fig. 3 also shows, on a much enlarged scale, the respective edges 11 of mica strips 9 and the respective edges 12 of the metallization layer 10 covering the outer surface of the strips 9. It will be noted that, while the adjacent layers 10 present a substantially continuous surface for the impact of the writing and reading beams, they are in fact separated from each other by the edges 11 of the strips 9, since these edges are not metallized. This separation is sufficient to insulate the elementary condensers from each other.

In Figs. 1 and 2, it was assumed that strips 9 partially covered the inner periphery of the core 8. However, it may be more convenient to arrange the strips 9 on the outer periphery of the ring 8. Returning now to Fig. 1, it may be seen that the tube further comprises collecting electrodes 13 and 14 in the writing space, in the shape of truncated cones centered on the axis X'X of the tube. The collectors 13 and 14 are raised to a potential of about volts with respect to core 8 and electrically connected to metallization 15 of the tube envelope. Two collecting electrodes 16 and 17 are also provided in the reading space. They are grounded through resistance 21 and are electrically connected to metallization 18. Cathodes 3 and 4 are raised to potentials of the order of -l00 volts with respect to the tube envelope. The electrodes 13, 14, 16, 17 are of a known type and therefore shown very schematically while their electrical connections have been fully shown. Their construction and mounting are known to those skilled in the art; for instance central electrodes 14 and 16 may be secured to the target by means of any electrically insulated mechanical connection, and peripheral electrodes 13 and 15 to an annular shield, not shown, arranged around the target and secured to the latter by means of insulating supports. The target itself is preferably secured to a bracket, traversed by the connections for the output signal Ss, which is collected, through capacity 22, across the resistance 21.

The target of Fig. l operates as follows: under the impact of beam 5, the metallized surface 10 of the strips 9 looses secondary electrons which are captured by electrodes 13 and 14 raised, as indicated above, to a positive potential of the order of 100 volts, for example. The rate of secondary emission being greater than 1, positive charges appear on metallized surface 10. The potential of ,the latter cannot, however, exceed that of electrodes 13 and 14; These charges are transmitted to portions of the metallized surface comprised within the reading space.v In this way, the above described elementary condensers thus carry acertain charge of at most 100 volts. Reading beam 6 similarly causes secondary emission on the part of metallizations 10 comprised within the reading space. Electrodes 16 and '17, being atzero potential,

repel these secondary electrons which fall back onto metallizations 10. Through the impact of the primary and secondaryelectrons on metallizations 10, the elemeutary condensers are discharged; when the potential of rnetallizations 10 has dropped to a'sufficiently low value, the'secondary electro'nscan be captured by electrons 16. and 17;. It, is known that, in these conditions, an output signal is obtained corresponding to the image impressed on the target under the action of theinput signal; V i

The above described mode of operation is analogous to that of certain known targets in storage tubes, but the particular shape of the target according to the invention ensures total independence of the writing and reading spaces, good efficiency and high target resolution.

. What I claim is:

I 1. A double-sided target for a storage tube of the type comprising a writing gun, a reading gun located on either side of said target and in which said target is scanned 'in a circle, said target being in the form of a ring, consistingrof a central conductive core having at least a portion of'its surface covered with similar thin strips partly overlapping each other in a uniform way, said portion being symmetrical with respect to two planes of symmetry of said core perpendicular to each other, said strips constituting an insulating layer whose external surface paral- 5. A double-sided target according to claim 12, wherein the'strips are of mica metallized with gold. v

6. A storage tube comprising in a same evacuated envelope, a writing gun located at one end of theftube, a reading gun located at the other end of the tube, a target positioned centrally of the tube for electrons emitted by the respective guns to impinge upon opposite sides'thereof and comprising an annular core of conductive material, thin strips of insulating material covering at least I a portion of the core surfacetsymmetrical with respect it to two mutually perpendicular planes of symmetry of the core, the thin strips overlapping each other uniformly i to constitute a layeiyand a metalliccoating 'onthe' ex ternal surface of said strips parallel to the surface of the core thereby to constitute elementary condensers each defining-a point of the target, energizing-connections to lel to thersurface of said ring is metallized, whereby they form, together with the conductive core, elementary condensers constituting a point of the target. 7

the guns and target including a signal inputterminal for the writing gun, and collector electrodes --for the respec-- tive sides of the target including a signal output on the reading gun side thereof.

References Cited in the file of this patent i UNITED STATES PATENTS, 2,185,684 Bennett Jan. 2, 1940..

' FOREIGN PATENTS Rosencrans Jan. 30, '1945 Great'Britain June

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