US2443547A - Dynode - Google Patents

Description

Ju'nevl5, 1948. P, K. wElMER I 2,4*L'?,5474

' DYNQDE Filed Aug. 21, 1.9/15L IN VEN T0?.

l fram/KY Patented June 15, 1948 Paul K. Weimer, Princet Radio Corporation of America,

of Delaware on, N. J., assgnor to` a corporation Application August 21, 1945, Serial No. 611,"720 9 Claims. y(Cl. Z50-'175) This invention relates to television tubes and multiplier dynodes therefor.

In my co-pending application, filed September 16, 1944, Serial No. 554,494, now U. S. Patent No. 2,433,941, issued January 6, 1948, I have disclosed a type of multiplier dynode having a pluralityof radiating inclined blades adapted to be positioned over the gun behind the rst anode, which act as the second and subsequent dynodes of the multipliers. This construction has proved quite elicient due, among other things, to theY symmetrical location around and back of the beam path. To shield the second and subsequent dynodes from the potentials of the electrode members infront, a shield screen was conductively fastened to these dynode units, so that electrons would be more effectively attracted to the next dynode in the rear. The bombarding electrons passed through the meshes of this screen effectively,.but the screen, of course, casts a shadow on the multiplier blades and collects electrons in proportion thereto. This, with other characteristics of that form of multiplier, limited the efciency to about 85% of the secondary emission ratio of the dynode.

It is an object of this invention tov constructa multiplier dynode that obviates the use of a shielding screen in a multiplier unit for protecting the emittedsecondary electrons from the suppressing eld of preceding electrodes.

Another object ofthe invention isto construct a multiplier dynode assembly around the gun, so that the dynode blades themselves shield the emitted secondary electrons from preceding fields without reduction of the entrance area for the bombarding primary electrons.

Other objects will appear in the following specification, reference being had t the drawing, in which:

Fig. 1 is a section through the dynode units ofthe multiplier, being taken through the plane l--I in Figs. 2 and 3, viewed in the direction of the arrows.

Fig. 2 is a front view of a dynode unit of Fig.

l, this figure being broken away to show onlyv onequarter of the complete circular dynode.

Fig. 3 is a diagrammatic partial sectional illustration of the manner of stamping and the arrangement of the dynode blades, the section being taken on the line 3-3 of Fig. 1, certain parts being omitted for clarity of illustration.

Fig. 4 is a sectional view similar to that of Fig, 3 illustrating a diierent way of stamping the vanes.

Referring' to the drawing, the cathode beam 2 tube in which the multiplier dynodes are illustrated consistsof a cathode l heated by coil 2. The front end of this cathode will have a suitable surface or coating for emitting electrons when heated. Grid or control member 3 surrounds the cathode and has a small opening 4 in its end adjacent the center of the cathode. This opening` is shown greatly enlarged over the mil diameter ordinarily employed. First anode 5 surrounds the grid and hasan end 6 adjacent, and in front of, the grid 3. This end is of suitable metal, or is coated with material for good emission of secondary electrons under bombardment by thel returning portion 'l of the beam Ii, which is projected at high velocity through the opening 9 in front of the opening 4 in the grid'. The opening 9 is usually of the order of 2 mills in diameter. Surrounding the tubular first anode 5V may be an insulating tube IIJ onl which are mounted the dynodes. The dynodes also may be supported from the periphery, as later explained, but either type of support may be used alone, if desired.

As many multiplying dynodes as desiredmay be assembled on the first anode back of the first dynode 6, but by way of example I have shown four. To provide for proper entry of the secondary electrons in my improved dynodes, it is preferable to use a. second dynode I I with shield screen I2 lwelded or soldered thereto, as in my said application. After this type of second dynode I use-my improved type, consisting of three dynodes, I3, I4, I5 having radial vanes formed into trough-shaped members. 'Ihese constitute the third, fourth and iifth multiplying stages, the first stage being the disc 6, as alreadyy indicated. There would be a final collecting electrode in a complete installation mounted on the gun to the rear of the dynode I5, but this is not a part of the invention claimed herein and it is shown only in dotted lines in the diagrammatic illustration of Fig. 3. The dynodes I3, I4, I5 have the same general construction, but Athe .L troughs of alternate dynodes extend in reverse directions, as made clear in Fig. 3.

Each dynode disc of this invention is stamped from a sheet of -about 5.mils thickness of silvermagnesium alloy or other suitable metal having good secondary emission properties. The dynode is circular and has a central4 circular hole I6` of the properl diameter toiit over theY insulating tube I0 or is properly spaced from the tubular rst anode 5, if the yinsulation isto be omitted. The dynodes may be stamped in diiferentways, two of which are shown in the drawing in Figs. 3" and 4. The form illustrated in Figs. 1 and 2 is shown in Fig. 3. In this form the vanes are cut by suitable dies and tools from the disc I'I at the radial lines passing through points I8 and I8 and bent 45 counter-clockwise around the radial Ilines passing through points I9 and I 9', leaving openings through the disc between the radial lines I8, I9. The portion between the radial lines I8 and IS and I8', I9 is uncutmetal and may be made as small as desired. The vanes are of such length as to leave the disc uncut at the periphery at Ia and around the opening I6 at I 8b, to give the disc proper rigidity. Then, the outer half ISa of the stamped-out blades is bent an additional 90 to form troughs 2li. Thus, one side is bent 45 to the plane o-f the disc and the other one 135. While the particular angle between the sides of the trough need not be 90,

as given, this is a suitable angle for eflicient operation of the dynodes.

The periphery I8a of the disc is then clamped over a supporting ring 2I of 30 mil nichrome wire or equivalent and-to the surface of this clampedover portion may be welded, or otherwise secured, supporting brackets 22 .properly spaced around the periphery. As indicated in the drawing, there are four of such brackets. These wouldv be fastened to suitable supporting insulation rods `23 within the tube, for example, as in the application of S. V. Forgue, .led February .'7, 1946, Serial No. 646,075, but since the supporting means is not part of the invention claimed herein, it is not shown in complete detail.

.The troughs of the third dynode I3 are shown facing to the right in'Fig. 3, though of course this could be the reverse without changing the invention. The fourth dynode I4 is stamped so that the troughs face in a vdirection reverse to that of the previous dynode I3 and is-positioned with one side |90l substantially parallel to and properly spaced from a side of a troughl of dynode I3. The troughs of the fifth dynode I are stamped similarly to those of the third dynode I3, so as to face in an oppositedirection to those electrons, as at 2l (Fig. 3), as in my said application. These vanes are stamped 45 from the disc I1 and are preferably twice the width of the blades or sides of the trough shaped stampings of dynodes I3, I4 and I 5. The secondary electrons 21, instead of passing through a screen attached to the succeeding dynode, as in that prior application, pass directly to the surfaces 28 of the troughs of the iirst dynode I3. Since there vis'rio shield screen for the electrons to pass through, there is no shadow cast on the surfaces of sides 28 and all electrons land thereon under influence of the higher potential of third dynode I3. These secondary electrons 2 are suitably shielded fromv the preceding potentials by sides ISa of the troughs of the third dynode, without using a screen. Electrons in an electrostatic lield rare'accelerated in paths perpendicular to the equipotential lines thereof and the eld is such that the electrons leaving vanes 25 cannot take the shorter paths to the sides or vanes of the troughs 20 that are parallel thereto but must continue o-n to the sides 28 perpendicular to vanes 26. A complete explanation of the theory of the travel of electrons in multiplier i'lelds is contained in an article by V. K. Zworykin and J. A. Rajchman, in I. R. E. of September 1939, page 558, and further explanation need not be given here. The` secondary electronsY emitted by the sides 28 are accelerated to the sides 3i of the .next dynode Ist without passing through any screen electrodes. The sides Idd of the troughs of the fourth dynode adequately shield these secondaries from preceding potentials. Hence, no shadow is castv on the emitting surfaces of sides SI and all electrons land thereon. rThe secondary electrons emitted by the sides 3l of the troughs of the fourth dynode, with a side I90L substantially parallel to and spaced from a side of a trough of dynode I4. All of this arrangement is clearly shown in Fig. 3.

If there are to be additional multiplier dynodes, they would be stamped, arranged and asf sembled in a way that rwill now be apparen without further description. Y

The manner in which my improved multiplier dynodes operate will now be explained:

The various electrodes would be connected to suitable terminals V1 to Vv, having voltages known to those skilled in the art, and these need not be specified. The electrons emitted by the end of the cathodeY I are controlled by the grid 3 and projected at high velocity as a beam 8 through the small opening 9 in the end of the first anode 5. The beam would be controlled in the usual way by deflecting fields, wall coating and decelerating ring, or equivalents, as disclosed,

for example, in my said application. After be- The returning electrons of the beam of the fourth dynode are attracted to the rear and bombard secondary electrons 33 from the sides 34 of the-troughs of the fth dynode, which are similarly shielded from previous potentials by the sides E9e. The secondaries 33 pass to a collector electrode 31, to which the output terminal of the multiplier would be connected.

In my invention I am able to get substantially emission efficiency in the dynodes I3, Ill and I5, because no shield screens are used therewith. The sides of the troughs suiciently modify the potential field distribution so that the secondary electrons emitted by the other sides of the troughs are attracted to succeeding dynodes without passing through shielding screens. In Fig. 4 the method of stamping of the radial vanes is somewhat different. Instead of stamping the troughs out of single openings between It and I9' as in Fig. 3, one side 38 is stamped down in the figure and is bent clockwise 45 around the radial line passing through the point 39, being cut from the disc at the radial line intersecting the point fifi. The other side of the trough is then stamped at the radial line of point 'i0 and bent clockwise around the radial line at point 4I slightly spaced from point 3Q. In this method of stamping, the sides of each trough meet in the plane of the disc and the openings in the disc, through which the electrons pass, lie between the radial lines at points 33 and di.

In the stamping method of both Figs. 3 and 4, the side of the trough stamped and bent the lesser yangle of 45 has a web l2 connecting the outer and inner ends of the trough sides to the uncut rings Isa and I8b of the disc. The length of these end webs depends upon the malleability of the metal of the disc. In general, these webs will extend from the apex over a fraction, only, of the ends, but the length is suiicient to add considerably to the rigidity of the dynode.

While I have chosen particular angles for the blades of the improved multiplier dynode, it will be understood that different angles may be chosen When desired.

Various modiiications of the invention may be made Without departing from the spirit of the invention.

Having described my invention, what I claim 1. A dynode disc for electron multipliers having a plurality of pairs of vanes stamped therefrom into troughs with the sides of the troughs making predetermined angles With each other and With the plane of the disc and the bisecting plane of the troughs being parallel to the disc to permit electrons to strike one side of the trough through the openings from Which said vanes are stamped.

2. A dynode disc for electron multipliers having a plurality of pairs of vanes stamped therefrom into troughs with each side of the trough making an angle with the plane of the disc per- |mitting electrons to strike a side of the trough through the openings from which said vanes are stamped, one of the sides of each trough being connected with the disc adjacent the periphery and central portion thereof and the bisecting plane of the troughs being parallel to and spaced from the disc.

3.. A self-shielding dynode disc for electron multipliers having a plurality of pairs of vanes stamped therefrom into troughs with each side of the troughs making an angle to the plane of the disc and the bisecting plane of the troughs being parallel to and spaced from the disc, one side of each trough adapted to shield secondary electrons bombarded from the surface of the other side by electrons entering through the openings in the disc from which said vanes are stamped.

4. A self-shielding dynode disc for electron multipliers having a plurality of pairs of Vanes stamped therefrom into right-angle troughs with one side of the trough making an angle of 45 to the plane of the disc and the bisecting plane of the troughs being parallel to and spaced from the disc, one side of each trough adapted to shield secondary electrons bombarded from the surface of the other side by electrons entering through the openings in the disc from which said vanes are stamped.

5. A dynode disc for electron multipliers having vanes formed into radial troughs positioned at one side of the disc and the bisecting plane of the troughs being parallel to and spaced from the disc, one side of the trough being integrally joined to the disc and the other side facing an opening in the disc formed by the cut-out vane of an adjacent trough.

6. A dynode disc for electron 'multipliers having vanes formed into radial troughs positioned at one side of the disc and the bisecting plane of the troughs being parallel to and spaced from the disc, one side of the trough and a part of its outer end being integrally joined to the disc and the other side of the trough facing an opening in the disc Iformed by the cut-out vane of an adjacent trough.

'7. A multiplier for television pick-up tubes comprising a plurality of axially aligned and spaced discs constructed as outlined in claim 1, with alternate discs positioned with the troughs facing in opposite directions With one side of a 'trough overlapping a side of a trough of an adjacent disc, and a cathode beam gun extending through the central holes of the discs and insulated therefrom.

8. A circular dynode disc for electron multipliers having a plurality of radial openings, a plurality of radial troughs joined to the disc at the edges of said openings to face in the same peripheral direction, the bisecting plane of the troughs being parallel to the plane of the disc.

9. A dynode disc for electron multipliers having a plurality of openings, vanes joined to said disc at the sides of said openings and extending at an angle to one side of the disc and additional vanes joined to said disc at said sides of the openings and extending at an angle to the other side of the disc to form troughs With the first mentioned vanes.

PAUL K. WEIMER..

REFERENCES CITED The following references are of record in the nle of this patent:

UNITED STATES PATENTS Number Name Date 2,246,172 Hergenrother June 17, 1941 2,254,128 Van Den Bosch Aug. 26, 1941

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