US2216267A

US2216267A - Electron multiplier

Info

Publication number: US2216267A
Application number: US205842A
Authority: US
Inventors: Flechsig Werner
Original assignee: FIRM FERNSEH AKTIEN GES
Current assignee: FIRM FERNSEH AKTIEN GES; FIRM FERNSEH AKTIEN-GESELLSCHAFT
Priority date: 1937-05-04
Filing date: 1938-05-03
Publication date: 1940-10-01
Anticipated expiration: 1957-10-01
Also published as: BE427837A; DE889657C; GB514335A; DE901569C; DE907097C; NL59576C; FR837484A

Description

W. FLECHSIG Oct. 1, 1940.

ELECTRON MULTIPLIER Filed May 3, 1958 Patented Oct. 1, 1940 UNITED STATES 2,216,267 ELECTRON MULTIPIJER Werner Flechsig, many, assignor Berlin-Charlottenburg, Gerto the firm Fernseh Aktien- Gesellschaft, Zehlendorf, near Berlin, Germany Application May 3, 1938, Serial No. 205,842 In Germany May 3, 1937 4 Claims. (011250-175) This invention relates to electron multipliers in which an alternating current is amplified by means of secondary emission, and'particularly it relates to such electron multipliers which consist of a series of foraminated electrodes held at increasing direct-current potentials whereby primary electrons impact one side of the electrodes and are drawn to the other side.

Such electron multipliers are known in the art,

and it is the object of this invention to overcome wholly or in part certain defects inherent in constructions known so far. These defects and means for overcoming the same shall be described in detail in the following:

Referring to the drawing, Fig. 1 is a longitudinal sectional View of an electron multiplier of the type described in which an embodiment of the present invention is incorporated. Fig. 2 is also a longitudinal sectional view of a multiplier in which an embodiment of the present invention is incorporated.

Multipliers of the type mentioned, consisting of a series of foraminated secondary-emitting electrodes, such as, for instance, wire-mesh grids,

possess the advantage over other multiplier structures that special means for concentration .of the electron stream between two emitting electrodes is not required. The vast majority of electrons travel along the desired predetermined paths be- 30 tween respective electrons.

However, it has been found that the few stray electrons not traveling along the desired paths can cause disturbances also in this type of multiplier, these disturbances resulting in non-uniform 35 amplification and corresponding distortion of the output current. These stray electrons can, for

instance, impact the glass wall of the vacuum receptacle and produce undesired charges thereupon. Furthermore, individual stray electrons may, in this manner, travel along paths avoiding the influence of the control electrode, and also missing the secondary-emitting electrodes.

Furthermore, phenomena were observed in a tube in which the emission produced by an indirectly heated cathode was controlled by a control grid and then multiplied, these phenomena being explained only by the presence of ions in the tube.

These ions penetrated into that portion of the vacuum receptacle in which the control of the emission takes place and caused considerable field distortions in that space or caused liberation of secondary electrons.

This invention provides for means to prevent the flow of such ions into the control-grid space,

55 and to prevent simultaneously other disturbances sired paths.

caused by stray electrons traveling along unde- To this end, the invention provides for dividing the interiorof the vacuum receptacle into several chambers partially separated from each other by means to be described below. As 5 it is necessary toblock the path for carriers of negative as well as of positive charges, an electrostatic blocking potential cannot be used. The separation of the above-mentioned chambers must, therefore, be mechanical. In practice, a 10 wall consisting of insulating material will be used to separate the individual chambers from each other, this wall possessing an aperture covered by a foraminated secondary-emitting electrode, by means of which the electron stream is allowed to 15 pass from one chamber to the other. Ions as well as electrons can then pass only through the foraminations of these electrodes from one chamher into another, all other paths being blocked. The first foraminated electrode following the con- 20 trol grid can then be used as an ion collector.

In Fig. 1, a tube is shown which is divided in the above-described manner into two chambers. The control of the emission takes place in one chamber, while amplification by secondary emission takes place in the other. The tube l includes an indirectly heated cathode 2, and a control grid 3. Secondary-emitting grids 4 are located in the chamber separated from the control-grid space by glass ring 5, which is fused to the Wall of the vacuum receptacle.

In the tube shown in Fig. 2, two separating walls are provided. At one end is a photoelectric cathode 2 upon which a light beam of undulating intensity may be incident. Two glass rings 5 are fused to the wall of the vacuum receptacle l. The ring closer to the anode possesses a greater inner diameter than that on the side of the cathode, in order to leave suflicient space for introducing electrodes in the construction of the tube.

Of course, various other embodiments of the invention are possible; in particular, the separating wall can be constructed in various ways. Finally, it is also possible to allow certain or all secondary-emitting electrodes to extend to the walls of the vacuum receptacle and into close contact along the entire periphery of each electrode so that there is no longer a free space between electrode and glass wall through which ions or electrons may travel. It is important only that electrons and ions can travel from one chamber to another only through the foraminations in the emitting electrodes because all other paths, particularly that along the walls of the tube, are blocked.

The described division of the vacuum receptacle may also be applied to other types of electron multipliers. It is also within the scope of this invention to provide a separating wall in the manner described between each two stages so that each individual chamber contains only one emitting electrode.

Having thus described my invention, I claim:

1. Electron multiplier, comprising a vacuum receptacle, an electron source, a plurality of foraminated secondary emissive electrodes supported transversely of said receptacle with their edges in spaced relationship to the Wall of said receptacle, and a collector electrode, said vacuum receptacle having a partition of insulating ma,- terial between said source of electrons and said secondary emissive electrodes andextending inwardly from the wall of said receptacle a distance at least equal to the space separation of the edges of said electrodes from said Wall.

2 Electron multiplier, comprising a vacuum receptacle of glass, an electron source, means for control of the emission from said electron source, a plurality of foraminated secondary emissive electrodes supported transversely of said receptacle with an edge thereof in spaced relationship to the wall of said receptacle, and a collector electrode, said glass receptacle having a partition of glass extending inwardly from said wall to a distance at least equal to the space separation of said edge from said wall and located between said source and said secondary emissive elec trodes.

3. An electron discharge device comprising an envelope, a cathode, an electron multiplier grid, a collector electrode, said grid being positioned between said cathode and said collector electrode with the edges of said grid in spaced relation to the inner Walls of said envelope, and a ring of insulating material extending inwardly from the inner Walls of said envelope past the outer edgesof said grid and forming with said grid a partition dividing said envelope into two chambers, one chamber containing said cathode and one containing said collector electrode.

4. An electron discharge device comprising an envelope, a cathode, a. plurality of electron multiplier grids, a collector electrode, said grids being positioned between said cathode and said collector electrode with the, edges of each grid in spaced relation to the inner walls plurality of rings of insulating material extending inwardly from the inner walls of said envelope past the outer edges of respective ones of said grids and forming with said grids partitions dividing the interior of said envelope into a plurality of chambers, one of said chambers containing said cathode and another of said chambers containing said collector electrode.

WERNER FLECHSIG.

of said envelope, and a I