US3684910A

US3684910A - Electron multiplier having dynode modules

Info

Publication number: US3684910A
Application number: US38092A
Authority: US
Inventors: Guy R Stutzman; Allan J Comstock
Original assignee: Deutsche ITT Industries GmbH
Current assignee: TDK Micronas GmbH; ITT Inc
Priority date: 1970-05-18
Filing date: 1970-05-18
Publication date: 1972-08-15
Anticipated expiration: 1989-08-15
Also published as: FR2091729A5

Abstract

An electron multiplier construction formed of a plurality of dynode modules. Each module is formed of a a ceramic wafer having two complementary, metal dynode elements attached thereto arranged to direct a stream of electrons through an opening in the wafer and into a dynode element of the next successive module. The modules are secured together in spaced, parallel relationship by metal post elements spaced-apart around the periphery of the wafers, each dynode element being connected to a different one of the post elements.

Description

[151 3,684,910 [451 Aug. 15, 1972 United States Patent Stutzman et al.

2,464,076 3/1949 De Gier...................313/70 X 2,757,307 7/1956 Six et al. ................313/257 X 3,229,143 H1966 Bartschat...................313/105 Primary Exanu'nerRobert Sega] Att0rney--C. Cornell Remson, J12, Walter J. Baum Percy P. Lantzy, Philip M. Bolton, Isidore To a gut,

Charles L. Johnson, Jr. and Hood, Gust, Irish & Lundy graph Corporation, Nutley, NJ.

221 Filed: May 18,1970

211 Appl.No.: 38,092

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ATTORNEYS PAIENTEDws 15 m2 SHLEI 3 OF 4 INVENTORS GUY R. STUTZMAN ALLAN J. COMSTOCK X/MO,M,M

ATTORNEYS PATENTEDAUB 15 m2 SHEET b [1F 4 lE lE INVENTORS BACKGROUND OF THE INVENTION '1. Field of the Invention This invention relates generally to electron multiplier constructions, and more particularly to a modular assembly of dynode elements for an electron multiplier.

2. Description of the Prior Art Conventional electron multipliers comprise a plurality of discrete stages or dynodes operated at progressively increasing potentials. The dynodes are formed of or coated with secondary emissive material and are arranged so that electrons injected into the low potential end of the device are multiplied upon dynode impact, thus resulting in the generation of secondary electrons which are accelerated to a succeeding dynode stage where the process recurs, hence giving rise to an overall cascade multiplication of electrons. An electron multiplier is commonly enclosed in an evacuated envelope and the progressively increasing potentials are normally obtained from an external resistance divider network and applied to the dynodes through a multilead stem. In conventional electron multiplier constructions, each of the dynodes is independently mounted and electrically isolated from adjacent dynodes thus providing a construction which is complex, difficult to assemble, and thus costly. Further, the use of such floating or free-standing dynodes results in a fragile construction which is not well suited to applications subject to shock.

SUMMARY OF THE INVENTION In order to provide a rugged electron multiplier construction, particularly suitable for use in airborne applications, the multiplier comprises a plurality of dynode age divider network are printed or otherwise deposited on the supporting members.

In its broader aspects, the invention provides a dynode assembly having a support plate member formed of insulating material with an opening therethrough. A pair of complementary dynode elements formed of relatively thin sheet material are respectively attached to the support member, the dynode elements being exposed to the opening and arranged so that a stream of electrons is directed from one dynode element to the other through the opening.

It is an object of the present invention to provide an improved electron multiplier construction.

Another object of the invention is to provide a rugged electron multiplier construction.

A further object of the invention is to provide an electron multiplier construction formed of a plurality of dynode modules.

A still further object of the invention is to provide a modular electron multiplier construction wherein each module includes resistance elements which collectively comprise a self-contained, voltage dividing resistance network.

2 BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of the embodiments of the invention taken in con junction with the accompanying drawings, wherein:

FIG. 1 is an exploded view in perspective illustrating one embodiment of the electron multiplier construction of the invention;

FIG. 2 is a cross-sectional view, taken generally along the line 2--2 of FIG. 1, and further illustrating the electron multiplier construction of the invention assembled within an enclosed envelope;

FIG. 3 is a fragmentary view, partly in cross-section, illustrating the method of attaching the stem leads to the module supporting posts;

FIG. 4 is a view in perspective illustrating one form of dynode element usable in the invention;

FIG. 5 is a side view further showing the electron multiplier of the invention using the dynode elements of FIG. 4;

FIG. 6 is a perspective of another form of dynode element usable in the invention;

FIG. 7 is a side view showing a modular construction employing the dynode elements of FIG. 6;

FIG. 8 is a top view showing a wafer element employed in another embodiment of the invention;

FIG. 9 is a top view of one dynode module assembled with the wafer element of FIG. 8 and having voltage dividing resistance elements printed on the wafer element;

FIG. 10 is a fragmentary cross-sectional view taken generally along the line 10-10 of FIG. 9;

FIG. 1 1 is a schematic illustration showing a modular electron multiplier assembly and voltage divider network incorporating the modules of FIG. 9; and

FIG. 12 shows the arrangement of the individual modules and voltage dividing resistors to provide the assembly of FIG. 1 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2 of the drawings, the improved modular electron multiplier assembly of the invention, generally indicated at 10, is shownas comprising five dynode modules 11, 1.2, 13, 14, and 15. Each of the modules comprises a circular supporting plate or wafer 16, preferably formed of ceramic material, and having a rectangular opening 17 therethrough adjacent the center. A pair of complementary, bucketshaped dynode elements formed of relatively thin sheet metal having secondary emissive properties, or being coated with secondary-emissive material, is positioned in the opening 17 of each of the ceramic wafers 16, the dynode elements being disposed to receive an input stream of electrons, to direct and accelerate the stream from one of the dynodes to the other through the respective opening 17, and finally to direct and accelerate the stream to the input dynode of the next successive module.

More particularly, a pair of identical,

complementary dynode elements

18 and 19 are provided seated in opening 17 of ceramic wafer 16 of module 11, dynode 18 being the input, low potential dynode for receiving an input stream of electrons, as indicated by the dashed line 20 in FIG. 2. In response to the application of suitable potentials to

dynode elements

18 and 19, the stream of electrons is directed and accelerated from dynode element 18 to dynode element 19, and thence to dynode element 22 of the next successive module 12, as shown by the dashed lines 23 in FIG. 2, and as well known to those skilled in the art.

Dynode elements

18 and 19 are respectively provided with opposed, outwardly extending

ears

24, 25, and 26, 27 which engage the upper side 28 of ceramic wafer 16, being rigidly attached thereto, such as by spot welding to a pad metalized on wafer 16, as indicated in dashed lines at 31.

Similarly, module 12 comprises ceramic wafer 29 and

dynode elements

30 and 32, module 13 comprises ceramic wafer 33 and

dynode elements

34 and 35, module 14 comprises ceramic wafer 36 and

dynode elements

37 and 38, and module comprises ceramic wafer 39 and

dynode elements

40 and 42, all of the dynode elements being similarly positioned in the respective opening 17 and similarly rigidly attached to the upper side of the respective ceramic wafer by

ears

24, 25, 26 and 27. Inspection of FIG. 2 will reveal that the

dynode elements

18 and 19, 30 and 32, 34 and 35, 37 and 38, and 40 and 42 are disposed in conventional arrangement so that as to accelerate and multiply the stream of electrons successively from the input dynode element 18 to final or output dynode element 42.

The

ceramic wafers

16, 29, 33, 36, and 39 are maintained in spaced, parallel relationship by a plurality of 5 post members 43 equally spaced around the ceramic wafers respectively adjacent the peripheral edges, there being ten such post elements 43 between each adjacent pair of ceramic wafers in the illustrated embodiment in which there are ten dynode elements. Each of the post members 43 comprises a hollow metal tube 44 having its upper end 45 snugly seated in an opening 46 in the respective ceramic wafer and rigidly secured thereto, as by brazing, the interior wall of opening 46 having previously been metalized. The tubular spacing members 44 extend toward the adjacent ceramic wafer in a direction normal to the wafer, and have their other ends 47 abutting the upper end 46 of the adjacent tubular element. As shown in FIGS. 1 and 2, corresponding tubular spacing elements 43 are in axial alignment respectively to receive pins or stem lead wires 48.

The

modules

11, 12, 13, 14 and 15 are rigidly held in assembled relation by welding the stem lead wires 48 to the respective tubular spacing members 44. Referring particularly to FIGS. 2 and 3, each of the tubular spacing elements 44 preferably has a cut-out portion 49 formed therein exposing side wall portion 50 of the respective stem lead wire 48.

Welding electrodes

52, 53 are then respectively engaged with exposed portions 50 of the stem lead wire 48 and the tubular spacing elements 44, as shown in FIG. 3, application of a suitable potential thus spot-welding the stem lead wire 48 to the respective lower and upper tubular end spacing element 44-1 and 44-2 so as to hold the modules in assembled relation. The use of equal length tubular elements 44 permits precision spacing of the wafers.

It will now be observed that the circular array of 10 post elements 43 comprising the tubular space members 44 and stem lead wires 48 provide a convenient means for making electrical connections to the respective dynode elements. Thus, thick film

electrical leads

54, 55 respectively connect

cars

24 and 27 of

dynode elements

18 and 19 to the upper ends of post members 43-1 and 43-2. The

thick film conductors

54 and 55 are rigidly attached to the upper surface 28 of ceramic wafer 11, preferably being printed thereon by any conventional method. Similarly, thick film leads 56 and 57 respectively connect

dynodes

30 and 32 to the post members 43-3 and 434 leads 58 and 59 respectively connect

dynode elements

34 and 35 to post members 43-5 and 43-6, leads 60 and 62 respectively connect

dynode elements

37 and 38 to post members 43-7 and 43-8, and leads 63 and 64 respectively connect

dynode elements

40 and 42 to post members 43-9 and 43-10.

Particular reference to FIG. 3 will reveal that the lower end 47 of a respective tubular member 44 abuts the termination portion 65 of a respective lead which surrounds the respective stem lead wire 48, thereby insuring a good electrical connection to the respective stem lead wire.

Referring particularly to FIG. 2, the dynode module assembly 10 may be positioned within the cylindrical portion 66 of an enclosing envelope of a tube incorporating an electron multiplier, such as a photo-multiplier tube or image dissector tube, cylindrical portion 66 having an end wall 67 through which the projecting portions 68 of the stem lead wires 48, extend, being sealed thereto as at 69. A suitable target or collector electrode 70 may be positioned to receive the multiplied electron stream 72 from the final dynode element 42. In the case of an image dissector tube, an element 72 is provided extending across the tube and having aperture 73 through which the input electron stream 20 is passed to the initial dynode element 18, as is well-known to those skilled in the art.

Referring now to FIG. 4, the dynode elements employed in the embodiment illustrated in FIGS. 1 and 2 may comprise a bucket-shaped portion 74 of relatively thin metal which may be conventionally formed by etching from a blank and then by stamping to the desired configuration. A generally U-shaped member 75, likewise formed of relatively thin metal, embraces the lower part of portion 74, being secured thereto in any suitable manner, as by spot welding, and has mounting

ears

24, 27, and 25, 26 integrally formed thereon and extending outwardly therefrom, as shown.

Referring now to FIG. 5 in which the dynode elements of the type shown in FIG. 4 are shown assembled in the multiplier assembly 10 of FIGS. 1 and 2, it will be seen that the

cars

24, 25, 26, 27 of each dynode element are arranged in abutting relationship with the upper surface 28 of each

wafer

16, 29, 33, etc.

Referring now to FIG. 6, another form of dynode element 76 may be employed comprising a unitary bucket-shaped member 77 formed of relatively thin sheet metal and having integral supporting

ears

78, 79 formed thereon and extending outwardly thereon, as shown.

Referring briefly to FIG. 7 in which there is shown an assembly utilizing the dynode elements 76 of the type shown in FIG. 6, it will be seen that the dynode elements are disposed in cooperative relationship, as shown, with their mounting

ears

78, 79 respectively engaging both the upper and lower sides of the respective ceramic wafers, as shown.

Referring now to FIGS. 8-12 in which like elements are indicated by like reference numerals and similar elements by primed reference numerals, there is shown an embodiment of the invention in which a pair of voltage dividing resistors is printed on each wafer along with circuit connections so that, when the multiplier is assembled, the resistors on all of the wafers are coupled in a voltage dividing network. Here, ceramic wafer 16' is provided having peripheral holes 46' opening 17, and holes 80 formed therein, such as by punching before firing the ceramic, or by ultrasonic abrasive machining after firing. Wafers 16' may be formed of suitable ceramic material, such as a high alumina which is fired at an elevated temperature.

The interior walls of

holes

46, 80 and a small area surrounding the holes on the upper surface 28 of wafer 16' are metalized, as at 82, 84 (FIG. 10). Metalizing of the holes may be accomplished with a conventional screen process employing a suitable metalizing material, such as molybdenum manganese. Plugs 86 are formed of a suitable low expansion alloy, such as Kovar, are then inserted in the metalized holes 80 and brazed thereto, plugs 86 thus providing a rugged mounting for the dynode ears or tabs which are subsequently brazed thereto. The upper surface 28 of wafer 16' is then preferably polished in a lapping operation to render it suitable for use as a substrate for the circuitry to be printed thereon.

Dynode elements

18, 19 are then positioned in opening 17 and their ears 24', 25, 26', 27' spot welded to plugs 86, as at 88. Thick film resistors R1, R2 and

electrical leads

90, 92, 94 are then formed on upper surface 28 on wafer 16, as by means of screen printing or vacuum deposition. Tubular spacing elements 44 are then inserted in the metalized openings 46' and brazed thereto. In the illustrated embodiment, a total of 12 openings 46' and tubular spacing elements 44 are provided. It will be observed that in the case of a particular wafer 16' which forms the first dynode module 11' (FIGS. 11 and 12), lead 90 couples post member 43-1 to one end of resistor R2, lead 92 couples the other end of resistor R2 and one end of resistor R1 to ear 25' of dynode l8, and lead 94 couples the other end of resistor R1 to ear 26' of dynode 19 and to post element 43-3.

Referring now additionally to FIGS. 11 and 12, a suitable cathode 96 may also be coupled to post 43-1 by lead 98, and post 43-1 may be coupled to external terminal 100. In the second dynode stage 12, lead 102 couples post element 43-3 to resistor R3, lead 104 couples resistors R3 and R4 to dynode 30, and lead 106 couples resistor R4 and dynode 32 to post element 43-5. In module 13', lead 108 couples post element 43-5 to resistor R5, lead 110 couples resistors R5 and R6 to dynode 34, and lead 112 couples resistor R6 and dynode 35 to post element 43-7. In module 14' lead 1 14 couples post element 43-7 to resistor R7, lead 116 couples resistors R7 and R8 to dynode 37, and lead 118 couples resistor R8 and dynode 38 to post element 43-9. In the final dynode module lead 120 couples post element 43-9 to resistor R9, lead 122 couples resistors R9, R10 to dynode 40, and lead 124 couples resistor R10, dynode 42 and target or collector electrode to post element 43-11. Post element 413- has another external temiinal 126 coupled thereto.

It will now be seen that with the arrangement and connection of the resistors R1-R10 as above-described to the various dynodes and post elements 43, resistors R1-R10 are coupled in a voltage dividing network across

external terminals

100, 126. It will be observed that only two external connections are required and thus, that it is only necessary to bring the rod elements 48 of two of the post elements, i.e. 43-1 and 43-11 out through the envelope end wall 67. It will be seen further that only six of the post elements, i.e. 43-1, 43-3, 43-5, 43-7, 43-9 and 43-11 are employed for making connections to the voltage dividing resistors Rl-Rl0 and the dynodes, the remaining intermediate post elements being desirably employed only for providing a rugged assembly of the dynode modules.

It will be observed that the modular construction incorporating the

wafers

16, 29, et seq, and the post elements 43 can be employed to support the elements of tubes other than electron multipliers, and that all of the circuitry for the tubes, not merely voltage dividers, may be imprinted on the wafers.

It will be seen that each module is seperately assembled and forms a complete unit which can be tested, such as for output, prior to the assembly of the entire device. It will further be seen that the spacing between modules is precisely controlled by the post elements 43, and that the spacing between the modules may be varied, as desired, by merely varying the lengths of the post elements 43. Finally, it will be seen that the modular construction of the invention lends itself to miniaturization and in a specific embodiment, the wafers are approximately 0.9 inch in diameter. It will now be seen that the invention provides a modular electron multiplier assembly which is characterized by its ruggedness and ease of assembly from a relatively few number of readily fabricated component parts.

While there have been described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.

What is claimed is:

1. An electron multiplier comprising:

a plurality of pairs of successive longitudinally disposed electron multiplier dynodes,

a plurality of successive longitudinally disposed spaced parallel insulating support discs having centrally disposed openings, each disc supporting a complementary pair of said dynodes in said opening arranged to direct electrons from one dynode of said pair to the other, each said disc including a plurality of like apertures spaced around the periphery thereof and a plurality of hollow metal connecting posts mounted on each said disc and having an end extending from said apertures on one side of each said disc, said apertures and posts of each disc being aligned with said apertures and posts of each other disc, each said end extending the distance between discs to abut the opposite side of the next adjacent support disc, each pair of dynodes on each respective disc being connected between a selective pair of said posts different from each other disc, and

a plurality of lead wires passing through the respec:

tive aligned apertures and posts and connecting said plurality of aligned posts of successive discs together in a predetermined pattern for establishing progressively increasing potentials on successive dynodes, including two voltage dividing re sistors printed on said support disc and connected between each said dynode and a respective post on each said disc wherein one end of each of said resistors is connected to a respective post, the other ends of both of said resistors being connected to one of said dynodes, the other of said dynodes being connected to one of said posts, said successive pairs of dynodes being arranged in alignment for directing a stream of electrons from each pair through successive said pairs.

2. The assembly of claim 1, wherein one dynode of each respective said complementary pair faces one side of each respective disc and the other dynode of each said pair faces the other side of said disc.

3. The assembly of claim 2 wherein said support discs are formed of ceramic material.

4. The assembly of claim 3 wherein each of said posts comprise a metal tube attached to said support disc, and a pin element extending into said tube and attached thereto.

5. The assembly of claim 3 wherein each of said dynodes has a pair of ears extending therefrom, the ears of each of said dynodes being attached to a side of said support disc thereby attaching the respective dynode thereto.

6. The assembly of claim 5 wherein said apertures have metal plug members seated therein and secured thereto, said ears being respectively secured to said plug members.

7. The assembly of claim 6 wherein the walls of said apertures are metalized, said plug member being brazed to said metalized walls, said ears being welded to said plug members.

8. The assembly of claim 1 further comprising an enclosing envelope having a generally cylindrical portion closed by an end wall, said support discs being positioned in said cylindrical portion with their peripheral edges closely adjacent the inner wall thereof.

Claims

1. An electron multiplier comprising: a plurality of pairs of successive longitudinally disposed electron multiplier dynodes, a plurality of successive longitudinally disposed spaced parallel insulating support discs having centrally disposed openings, each disc supporting a complementary pair of said dynodes in said opening arranged to direct electrons from one dynode of said pair to the other, each said disc including a plurality of like apertures spaced around the periphery thereof and a plurality of hollow metal connecting posts mounted on each said disc and having an end extending from said apertures on one side of each said disc, said apertures and posts of each disc being aligned with said apertures and posts of each other disc, each said end extending the distance between discs to abut the opposite side of the next adjacent support disc, each pair of dynodes on each respective disc being connected between a selective pair of said posts different from each other disc, and a plurality of lead wires passing through the respective aligned apertures and posts and connecting said plurality of aligned posts of successive discs together in a predetermined pattern for establishing progressively increasing potentials on successive dynodes, including two voltage dividing resistors printed on said support disc and connected between each said dynode and a respective post on each said disc wherein one end of each of said resistors is connected to a respective post, the other ends of both of said resistors being connected to one of said dynodes, the other of said dynodes being connected to one of said posts, said successive pairs of dynodes being arranged in alignment for directing a stream of electrons from each pair through successive said pairs.