US2565515A

US2565515A - Electron multiplier with secondary emissive grids

Info

Publication number: US2565515A
Application number: US729222A
Authority: US
Inventors: Palluel Pierre Charles
Original assignee: International Standard Electric Corp
Current assignee: International Standard Electric Corp
Priority date: 1938-11-29
Filing date: 1947-02-18
Publication date: 1951-08-28
Anticipated expiration: 1968-08-28
Also published as: GB533807A; FR853971A

Description

Aug. 28, 1951 P. c. PALLUEL 2,565,515

ELECTRON MULTIPLIER WITH SECONDARY EMISSIVE GRIDS Filed Feb 18, 194'? FIG. 9

FIG. 1

4 FIG. 2'

FIG. IO

FIG. I 3

FIG. 8

I I INVENTOR. I

PIERRE CHARLES PALLUEL FIG, 7'

A TTORNEV Patented Aug. 28, 1951 ELECT-RON MULTIPLIERWI'EH SECONDARY EMISSIVE GRIDS Pierre Charles'Palluel, Paris, France; assignor to International Standard Electric Corporation, New York, N; Y., a-corporation of Delaware Application February 18, 1947, Serial No. 729,222" In'FranceNovember 29, 1938 Section 1, Public Law 690, August 8, 1946. Patent expires November 29, 1958 9 Claims. (erase- 17s) The present invention relates to electron discharge devices, and particularly electron discharge devices employing successive secondary emissions of electrons.

In particular, one of the objects of the'invention is to provide means: for increasing and'improving the high frequency response of such-devices, and to reduce their'weight andtheir size.

Another object of the invention is to provide electron discharge devices with successive second ary emissions of electrons in'which the'structure issuch that it avoids the use of electrical'o'r magnetic focussing arrangements.

It is also the object of the invention to provide electron discharge devices with successive secondary emissions of electrons, in which the structure is such that the drawbacks arising from'extraneous phenomena, such as dielectric charges involved in the structure, are practicallyeliminated.

It is also the object of the invention to provide electron discharge devices with successive secondary emissions ofelectrons in which the output is increased by the practically complete utilisation of the electrons. emitted in the structure and by the use of a large number of electrodes with high secondary emission.

It is also theobject of the invention to provide electron devices withsuccessive secondary emissions of electronsin which the risks of distortion due to the different transit times ofthe electrons along the structure are practically eliminated.

In the rest of thedescription the electrodes with secondary emission willbe called impermeable or impervious when the secondary electrons emitted under the impact of primary electrons on one of those electrodes are propagatedon the same side of the electrode structure as the primary electrons, while the electrodes with secondary emission will be called. permeable or pervious when the secondary electrons emitted under the impact of primary electrons on one of these electrodes are propagated'on the side of the electrode opposite to the side of the impact of the primary electrons, Whether the secondary electrons after having been released from the electrode pass through it, as in the case of the electrodes in the form. of emissive grids, or whether these electrons are directly released on the surface of the electrode opposite to the surface of impact of the primary electrons, as in the case of emissive electrodes in the form of suitably. treated metal sheets. In fact, the terms permeable and iinperme-able'," employed'to define the two'types of electrodes with secondary emission, only concern the secondary electrons emitted by these electrodes, these two types of electrodes being practically impermeable to the primary electrons which they always ha1e to arrest.

In accordance with on of the characteristics of the invention, an electrode structure of. discharge devices with successive secondary emissions comprises a set of electrodes practically impermeableto the electrons arranged so as todefine a substantially closed space, and a set ofielectrodes practically permeable tothe electrons.=ar'- ranged inside this closed space, the electrodesof the twosets having appreciable properties of secondary emission of electrons.

In accordance with another of its characteristics, the inventionprovides-electrode structures with secondary emission comprising alongv the structure electrodes permeable, and electrodes impermeable to the electrons in alternating sucicession.

, In accordance with another characteristiczof the invention, a structure with secondary emission is composed ofaseries ofamplifier cells, each comprising an emissive electrode-impermeable to the electrons and constituting the body of the cell, and two emissive input and output electrodes permeable to the-electrons andrespectively common to thepreceding cell, and to the following cell.

In accordance with another characteristic of the invention, an electrodestructure for ardevice with successive secondary emissions comprises electrodes permeable tothe electrons, andlelectrodes impermeable'to the electrons, all capable of-emitting secondary electrons under the impact of incidental electrons arranged in such a way that the mechanism of the successive secondary emissions of the structure is ensured by the arrangement of the structure itself.

In accordance with another characteristic of the invention, electrode structures in which the concentration of the electrons is ensured by the arrangement of the structure itself, comprises a plurality of i emitting electrodes permeable to the electrons, and'aplurality of emitting electrodes impermeable to the electrons.

In accordance with another ch'aracteristic oi the invention; electrode structures comprising both electrodes with secondary emissions permeable to the electrons, and other electrodes with secondary emission-impermeable to the electrons are arranged so as practically to prevent any electronemitted by anelectrode from passing freely to another electrode of the structure which does not immediately follow the electrode from which it proceedsin'th 'succession of the potentialsapplied to the'electrodes;

In accordance with another characteristic'of the invention, structures of" electron multiplier devices comprising a plurality of electrodes permeable to the electrons, and a plurality of electrodes impermeable to the electrons are arranged so that all the electrodes of the structure with the exception of the ensemble of collecting electrodes are arranged to emit electrons, no magnetic field of concentration being employed.

In accordance with another characteristic of the invention, control grids or electrodes or arrestor grids or electrodes not emitting electrons may be associated with electrodes of the multiplier structures.

In accordance with another characteristic of the invention, a primary structure of generation and control of the electrons may be associated with a structure with secondary emission such as defined hereinabove, an electrode with a secondary emission permeable to the electrons separating the primary structure from the secondary structure.

In accordance with another characteristic of the invention, in structures with successiv secondary emissions such as above, in which tubular emissive electrodes form a practically closed space for the electrons, an electrode with secondary emission permeable to the electrons is arranged between two successive tubular electrodes impermeable to the electrons along the whole length of the structure.

In accordance with another characteristic of the invention, these emissive electrodes permeable to the electrons inserted between two successive electrodes impermeable 'to the electrons may have their edges projecting beyond the practically closed space for the electrons formed by said electrodes impermeable to the electrons.

In a general manner, devices with successive secondary emission of electrons incorporating characteristics of the invention comprise electrodes impermeable to the electrons in the form of rings or tubular elements arranged one after the other so as to define a channel in such a way that an electron in movement inside this channel has only a very slight chance of escaping therefrom. These tubular or annular electrodes are separated by very small intervals with respect to their length, and in these intervals electrodes permeable to the electrons are arranged transversely with respect to said channel.

All these electrodes are treated by any suitable means in order to have a high power of secondary emission.

An emission electrode and primary electron control structure is arranged at one end of said channel, and an electron-collecting arrangement at the other end.

Potentials increasing from one electrode to the next are applied in any suitable manner to the electrodes of the structure with secondary emission constituted in this way, so that the electrons upon each impact have a speed suificient to secure good secondary emission and the forms and relative positions of the electrodes are chosen to create in themselves fields which ensure the correct paths of the electrons.

With such structures the electrons advance from one electrode to the next without any other concentration device than the electrodes themselves which, in particular, eliminates the drawbacks of concentration by magnetic fields.

Since practically no electrons escape from the structure, the current output is the best it can possibly be. Moreover, certain extraneous 4 phenomena such as those due to the dielectric charge are practically eliminated.

It should, moreover, be noted that the devices incorporating the characteristics of the invention because electrodes permeable to the electrons are associated with impermeable electrodes of which the co-efficient of secondary emission is higher than that of the permeable electrodes, will result in higher outputs than other devices using secondary emission and having an equal number of multiplication stages, and/ or with an equal overall potential which employ only electrodes permeable to the electrons which may be associated with one or a small number of impermeable electrodes.

Moreover, the structures of devices incorporating characteristics of the invention being such that all the electrons successively encounter all the electrodes and passing none without striking it, and consequently, without causing any emission therefrom, their time of transit only intervenes as a delay in the transmission, and not as a factor of distortion which occurs in the case of devices operating with high frequency, having a path open to the electrons of any electrode with secondary emission, to the output electrode or arrangement of electrodes when the electrons coming from the same electrode at the same time reach the output electrode at different moments after striking a difierent number of multiplication stages.

Various diagrammatic embodiments of structures of electron discharge devices incorporating characteristics of the invention are shown in a non-limiting manner on the attached drawings in which:

Fig. 1 shows in a general manner an arrangement of electrodes in accordance with characteristics of the invention;

Figs. 2 to 7 show schematically electrode structures in accordance with certain characteristics of the invention, in which the electrodes are arranged in linear succession, while in Fig. 8 the electrodes are arranged to give a zig-zag form;

Figs. 9 and 10 show by way of example two primary structures which may be associated with secondary electrode structures in accordance with certain characteristics of the invention; and

Fig. 11 shows schematically an electron multiplier structure incorporating characteristics of the invention.

Fig. 1 shows a unit of electrodes of any shape. The unit of electrodes with full secondary emission, or impermeable to the electrons such as Al and A2 defines a channel in which electrodes with secondary emission permeable to the electrons, for example, in the form. of grid or metal sheets, such as GI, G2 are arranged transversally. In another manner, it may be said that the complete structure is formed of coupled electron-multiplier cells, individually composed of a full electrode such as AI, and two permeable electrodes, an input electrode GI and an output electrode G2 of the cell, each permeable electrode being also a component element of the previous cell or the next cell respectively. With a structure of this kind any electron emitted by the permeable electrode GI under the impact of incidental electrons will strike the full tubular electrode AI from whence it causes to be emitted secondary electrons, which in turn will strike the permeable electrode G2, causing to be emitted therefrom secondary electrons which in turn will strike the surface of the full electrode A2, and

so on; along the structure.

electrode between two successive electrodes does not permit any electron to pass directly-from one full electrode to the next full electrode, or another subsequentelectrode of the structure and the potentials and the forms of these electrodes practically preventthe electrons from passing'directly'from one permeable electrodeto the next.

The impermeable and permeable electrodes may, moreover, 'be in particularly'suitable forms to facilitate correct operation of the structure. For example, full electrodes with symmetry of revolution such as cylindrical rings, or rings of polygonal section as in Figs; 2, 4 or 6 are particularly suitable. If the operative-currents are'more considerable, it may be well to" provide fullelectrodes progressively widening as the structure advances as indicated'in Figs. 3-and by way of illustration, any forms of widened electrodes with longitudinal axis of symmetry" being, moreover, suitable without the necessity of preserving an external enveloping surface of rectilinear section in the longitudinal direction.

In order to reduce still more'the possibilities of the electrons leaving thestructure,the electrodes permeable to the electrons may be arranged to have their edges projecting beyond the. spacedefined by the form of the full or impermeable electrodes in the intervals between these impermeable electrodes. Or again, the full electrodes maybe so shaped at the ends that they give a certain directive effect tothe stream of electrons which is to strike a permeable electrode, for example, the end of these full electrodes in front of each permeable electrode will have an area reduced with respect to its normal cross sectional area, or with respect to the area of the permeable electrode.

The sections of the successive cells composing the channel for the electronic fiux may, moreover, not be equal, or regularly increasing. As shown in Fig. '7. successive impermeable electrodes Al, A2 may have diiferent cross sections and be slightly overlapping which still more limits the chances that the electrons will escape from the secondary emission structure.

In order to favour the concentration of the electrons onto the permeable electrode following a full electrode, this permeable electrode may be of a form no longer plane, as in Fig. 2, but curved, for example, as a semi-spherical cup, as in Fig. 4, or any other angular or curved form, or as shown in Fig. 5 a co-axial shape, or other form of surface with longitudinal axis of symmetry entering the space defined by the following full electrode.

The permeable electrodes may also consist of sets of planes which intersect each other so as to offer one or more planes of symmetry passing through the longitudinal axis of the system, or may even consist of electrodes comprisin any surface of revolution, or a set of planes which intersect each other to form a basic surface which may, or may not, be a permeable plane, or any other shape.

Each of these permeable electrodes may, moreover, be provided, if desired, with a rectilinear extension preferably arranged along the longitudinal axis of the structure, as indicated in PI, P2 etc. on Figs. 6, 7, 9, 10, 11, these extensions bed ihg directed l towards the output side of the strumture: The extensions help direct the secondary electrons emitted by their associated permeable electrodes towards the surface of the following impermeable electrodes Al, A2 etc.

In the same way'structures, in accordance with characteristics of the-invention, may be arranged no longer with a longitudinal axis, but with an axis having any curves or bends desired, for example, so that the ensembled of the full electrodes forms a toroidal channel, or a channel with several bends. Fig.- 8 shows, by way of ex ample, a structure comprisingbent full electrodes, BI, B2, B3 etc., emitting electrons over their entiresurfaca'or from certain portions only, electrodes permeable to'the electrons, and emitting secondary electrons GI, G2 etc., being inserted between the successive full electrodes.

In a general manner, moreover, the electrodes employed may be arranged either to emit secondary electrons over their whole surface or over only a-portion of their surface.

Such electrode structures may be associated with any desired type of primary cathode, for example, cold or photo-electric cathodes, or hot or thermioniccathodes with direct or indirect heating. may be employed. Examples of such arrangements are shown in Figs. 9, 10 and 11 in which, moreover, are shown non-emissive control electrode structures. In Fig. 9 the first electrode withsecondary emission GI is struck by a primary stream of electronsemitted from a thermioniccathode K and controlled by a grid C. In Fig. 10 aprimary structure comprising several gridsC, CI, C2 and an anode R surround a cathode K. The secondary electrons emitted by R under the impact of the controlled stream is directed. onto the first permeable electrode with secondary emission GI; The electrode R, moreover, may consist of a deflecting or reflecting electrode, or an arrangement of such electrodes.

In Figs. 9, 10 and 11 the cathode and control electrode structure is arranged so that its axis coincides with that of the secondary emission structure, or at least extends this axis. This arrangement which, however, is not essential to the invention enables the advantages of grid control to be enjoyed, that is to say, of a high slope by using space charge. Fig. 11 shows by way of illustration a diagrammatic arrangement of a complete electron multiplier incorporating characteristics of the invention. This multiplier comprises an evacuated protecting envelope E enclosing a cathode K, thermionically emitting primary electrons, a control grid C controllin said primary electrons,.a first anode R emitting secondary electrons, a structure with successive secondary emissions comprising electrodes in the form of tubes Al, A2, A3, A4, associated with permeable electrodes GI, G2, G3, G4 individually provided with directional extensions Pl P2, P3, P4, and a terminal structure shown by way of example as comprising a last permeable plane electrode G5, a last full or return plate electrode A5, and a collecting electrode in the form of a grid 0 serving as output electrode. The various electrodes with secondary emission including the electrode R, are connected in order by means of taps of a resistance potentiometer RP, fed by a suitable source S. It is clear that the potentiometer and the source are only shown diagrammatically and may consistof any suitable power supply arrangement.

It will be seen that with structures incorporating characteristics of the invention devices are obtained occupying less space and of less weight owing to the fact that the amplifier stages are alternatively arranged along the axis of the structure and transversally with respect to this axis.

The various arrangements and electrode structures shown have onl been given by way of example in order to facilitate an understanding of the invention, and it is clear that numerous modifications may be made therein without departing from its scope with regard to the choice of the form of the individual electrodes, and of the input and output structures of the devices.

What is claimed is:

1. Electrode structure comprising a plurality of secondary emission cells in succession, each cell consisting of a tubular secondary emissive electrode impervious to electrons and two end secondary emissive electrodes pervious to secondary electrons mounted adjacent the ends of said impervious electrode, each end secondary emissive electrode being common to two successive cells.

2. Electron multiplier structures, comprising a plurality of electrodes pervious to secondary electrons and a plurality of separate tubular electrodes impervious to electrons in which all the electrodes of the structure but the collecting electrode arrangement are adapted to emit electrons.

3. Electron multiplier structures as claimed in claim 2, further comprising a primary electron generating and controlling structure, and a secondary electrode structure separated from said primary structure by a first separate secondary emission electrode pervious to secondary electrons.

4. Electron multiplier structures as claimed in claim 2, wherein control grids are associated with at least some of the secondary emission electrodes.

5. Electrode structures comprising a set of secondary emissive tubular electrodes impervious to electrons forming a practically closed space, a secondar emissive electrode pervious to secondary electrons being inserted between each two successive tubular electrodes.

6. Electrode structures as claimed in claim 2, each electrode pervious to secondary electrons having portions protrudin from said practically closed space.

7. Electrode structure as claimed in claim 2, each electrode pervious to secondary electrons being provided with a non-emissive projection protruding in the direction of the electron circuit.

8. Electrode structure as claimed in claim 5, wherein each of said tubular electrodes impervious to electrons is overlapped by the next subsequent tubular electrode to define more strictly said closed space.

9. Electrode structure as claimed in claim 2, wherein the successive electrodes of the structure are of increasing dimensions.

PIERRE CHARLES PALLUEL.

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

UNITED STATES PATENTS Number Name Date 1,920,863 Hopkins Aug. 1, 1933 2,102,045 Thomas H Dec. 14, 1937 2,143,095 Thomas Jan. 10, 1939 2,147,756 Ruska Feb. 21, 1939 2,190,914 Krenzien Feb. 20, 1940 2,233,878 Snyder Mar. 4, 1941