US3229143A

US3229143A - Electron multiplier device

Info

Publication number: US3229143A
Application number: US143403A
Authority: US
Inventors: Frederick L Bartschat
Original assignee: NUCLIDE CORP
Current assignee: NUCLIDE CORP
Priority date: 1961-10-06
Filing date: 1961-10-06
Publication date: 1966-01-11
Anticipated expiration: 1983-01-11

Description

Jan. 11, 1956 F. L. BARTSCHAT ELECTRON MULTIPLIER DEVICE Filed Oct. 6, 1961 6 SheetsSheec l I 1 i 49 5 f a p I a i 52 V I a 8 22f 2 INVENTOR F radar/ck L. Barfschaf BY Wig/$ ATTORNEY Jan. 11, 1966 F. L. BARTSCHAT 3,229,143

ELECTRON MULTIPLIER DEVICE Filed Oct. 6. 1961 6 Sheets-Sheet 2 INVENTOR Frederick L. Barfscha/ ATTORNEY Jan. 11, 1966 F. v BARTSCHAT 3,229,143

ELECTRON MULTIPLIER DEVICE Film 51cc. 6, 1961 6 Sheets-Sheet 5 ATTORNEY H, 1936 F. L. BARTSCHAT ELECTRON MULTIPLIER DEVICE 6 Sheets-Sheet 4 INVENTOR ATTORNEY Jan. 11, 1966 F. L. BARTSCHAT ELECTRON MULTIPLIER DEVICE 6 Sheets-Sheet 5 F'llcci Oct. 6, 1961 INVENTOR Frederick L. Barfschaf ATTORNEY Jan. 11, 1966 F. BA-RTSCHAT ELECTRON MULTIPLIER DEVICE 6 Sheets-Sheet 6 Filed Oct. 6, 1961 INVENTOR 8; Frederick L. Barfschaz BY W/ ATTORNEY United States Patent 3,229,143 ELEGIRON MULTlPLIER DEVICE Frederick L. Bartschat, State College, Pa., assignor to Nuclide Corporation, State College, Pa., a corporation of Nevada Filed Oct. 6, 1961, $81. No. 143,403 17 Claims. (Cl. 3131fl5) My invention relates broadly to multiplier devices and more particularly to a construction of electron multiplier device.

One of the objects of the present invention is to provide a construction of electron multiplier tube which provides magnetic shielding to prevent stray magnetic fields from entering the dynode region of the multiplier to thus provide a more accurate output.

Another object of the invention is to provide a :construction of electron multiplier tube which can be easily disassembled for cleaning and replacement of components.

A further object of the invention is to provide a simple and economical construction of electron multiplier tube having a substantially longer and more eflicient tube life, due to its construction, whereby it can be completely disassembled.

Still another object of the invention is to provide a simple and economical construction of dynode for electron multiplier devices.

Other and further objects of the invention reside in the manner in which the multiplier tube components can be easily assembled and disassembled as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which:

FIG. 1 is a side elevation view, partly in cutaway section, showing the assembled multiplier device of the invention and more particularly showing the manner in which potentials of varying magnitudes are applied to the various plates of the tube;

FIG. 2 is a vertical section view taken substantially along line 2-2 of FIG. 1;

FIG. 3 is a cross sectional view taken substantially along line 3-3 of FIG. 2;

FIG. 4 is a cross sectional view taken substantially along line 44 of FIG. 2;

FIG. 5 is a cross sectional view taken substantially along line 5-5 of FIG. 2, and particularly showing the dynode assembly;

FIG. 6 is a cross sectional view taken substantially along line 6-6 of FIG. 2, and particularly showing the output collector;

FIG. 7 is a plan view showing the stamping blank from which a dynode is evolved;

FIG. 8 is a rear perspective view of one of the dynode structures;

FIG. 9 is a front perspective view of the dynode structure of FIG. 8;

FIG. 10 is an enlarged vertical sectional view of a fragmentary portion of FIG. 2, and particularly showing the manner in which the dynode structures and their supporting components are assembled into the multiplier tube structure of the invention; and

FIG. 11 is an enlarged fragmentary sectional view taken substantially along line 1111 of FIG. 5 and particularly showing the manner in which the electrical leads are connected to the various multiplier tube plate and electrode elements.

The electron multiplier device of the present invention is of the type wherein the output of the tube is greatly increased by the use of secondary electron emission to multiply electrons and ions entering through the input aperture of the tube into the dynode multiplying channel. This is accomplished by causing the electrons that enter the multiplying device to strike a surface that is especially 3,229,143 Patented Jan. 11, 1966 p epared to give secondary electron emission. The secondary electrons thus produced are ejected and accelerated to another electrode or surface which is at a more positive potential to, in turn, give more secondary electrons, which in turn can be made to produce still more electrons, etc., by progressing the electron beam through the tube toward the output through dynodes or charged surfaces having progressively more positive potential thereon. Thus in this manner, the output of the multiplier device is immensely increased and the magnitude of the output is determined by the number of dynodes or charged surfaces through which the initial beam is allowed to progress.

Throughout the several views, similar reference numerals represent similar tube components. The electron multiplier of the invention is housed in a vacuum-tight envelope indicated at 1, constructed, for example, from Inconel metal and mounted at one end to the vacuum system on which the multiplier device is to be utilized and connected at the opposite end to a vacuum-sealing flange 2 which, in turn, is tightly sealed against the mounting flange 3 which carries protruding ridges there/around to cooperate with corresponding recesses in flange 2 to provide a tight vacuum seal intermediate the flanges. Access by the electrical input leads to the vacuum housing '1 is attained through the

input lead housings

4, 5, and 6, which are connected in sealing relation with mounting flange 3. The ion beam which is emitted from an unknown substance in a portion of the measuring system, not shown, is indicated schematically at 7, in FIG. 2 and, as indicated, is directed into the multiplier device of the invention through apertures in the

collectors

8 and 9, of known construction, and which are supported in the thin wall vacuum housing 1 in conventional manner. Briefly, the ion beam emanating from the unknown substance eventually becomes an electric current within the multiplier device, and the measurement of this current at the output of the tube renders an indication of the nature of the unknown substance.

Multiplier mounting flange assembly, indicated at 10, is secured to mounting flange 3 by means of screws 11 or other suitable mounting means. The mounting flange assembly carries a generally square top mounting plate 12 thereon having a central aperture 13 as shown more clearly in'FIG. 6. .An output lead mounting plate 14 is :carried interiorly of the multiplier mounting flange assembly and provides apertures thereon through which insulation lead-through members 15 extend and which are securely connected to output lead mounting plate 14 by ,means of a mounting clip 16 connected with the plate and engaging the flanges of lead-through members 15, so as to secure them in abutment with mounting plate 14. The insulation lead-through members 15 may be constructed of Pyrex, Carborundum, or other insulation material and provide a mounting for electrical output leads 17 and 18 which extend from the multiplier device through

output lead housings

19 and 20, securely connected in apertures in mounting flange 3 beneath the multiplier mounting flange assembly 10.

In the drawings, I have shown a preferred form of the invention showing a multiplier device, according to the invention, having sixteen dynode stages with sixteen dynode support plates, but it is to be understood that the number of dynode stages can be greater or fewer, depending upon the output current gain which is desired from the multiplier device. Experimentation has shown that acurrent gain in the range of 10 to 10' is obtainable with sixteen dynode multiplier devices as illustrated in the drawings, and a current gain in the range of approximately 10 -10 'is obtainable with a-twenty dynode multiplier device according to the invention.

-meral 21'. port plate 34 by means of screws 35, or other suitable securing means extending through the apertures of the parallel extensions 27, as more particularly shown in as beryllium metal copper alloy, Berylco, which can be a stamping or the like, from which the dynode structure, indicated generally at 21, in FIGS. 8 and 9, is evolved. The blank comprises a main body portion 22 carrying tabs 23 at the upper end thereof, and terminating in a lower body portion 24 at the opposite end thereof. Pie-shaped extensions 25 are connected with, and extend outwardly from, lower body portion 24 and carry arcuate edges 26 thereon which carry apertured extensions 27 in parallel relation. The adjacent edges of pie-shaped extensions 25, which are normal to each other, carry

tab extensions

28 and 29, respectively, and the tab extensions of corresponding edges of the opposite pie-shaped extensions are disposed in staggered relation to each other as shown in FIG-7. A T-shaped opening is defined on the initially flat blank intermediate the lower body portion 24, pieshaped extensions 25, and apertured parallel extensions 27, as shown.

As stated, the three dimensional dynode structure of FIGS. 8 and 9 is evolved from the initially fiat blank of FIG. 7. The pie-shaped extensions 25 are folded downwardly along fold lines 30 so as to be disposed normal to lower body portion 24. Main body portion 22 is then folded along fold-line 31 substantially back upon lower body portion 24 and is curved upwardly along the arcuate edges 26 of pie-shaped extensions 25, the tabs 23 then being folded normal to the upper edge of main body portion 22 to overlap the exterior surfaces of pie-shaped extensions 25 to secure the various members in relation to each other. The apertured parallel extensions 27 are then folded inwardly toward each other along fold-lines 32 so as to be disposed normal to the exterior surfaces of pie-shaped extensions 25 and'directed opposite thereto, as shown.

The entrance opening varies with every other dynode, as shown more particularly in FIGS. 2 and 10, wherein, in FIG. 2, the entrance opening for the ion beam 7 to the first dynode is along the side of the dynode along which 'tab extensions 28 are disposed and the entrance opening to the second dynode is the side of the dynode along which tabs 29 are disposed, and, alternately, so on until the end of dynode multiplier chain. The dynode illustrated in FIG. 9 corresponds to the dynodes in the second, fourth, sixth, eighth, tenth, twelfth, fourteenth and sixteenth positions in the dynode multiplier chain, while the remainder of the dynodes have their entrance face on the opposite side from that illustrated by the dynode of FIG. 9. The tab extensions, either 28 or 2.9, along'the entrance face of the dynode, are folded back upon the interior face of 'the pie-shaped extensions 25, as shown in FIG. 9, and a Nichrome wire 33 is wrapped back and forth between the staggered tabs on the opposed pie-shaped extensions 25 as shown, and the wire is spot-welded on either side of each tab to secure the same to the dynode structure.

Thus, six Wires are provided across the entrance face of the dynode and the

tab extensions

29 or 28, respectively,

along the opposite open face of the dynode are sheared 01f. Thus, the initial flat metal blank, as shown in FIG. 7, can be utilized for either configuration of dynode desired, by merely shearing off the extension tabs which are not needed for the particular structure. When "the dynode entranceis along the side carrying tabs 28 then the Nichrome wires are wrapped around these tabs and welded thereto, while tabs 29 are sheared from the pieshaped extensions 25.

In FIGS. 2 and 10 I have indicated the dynodes having their entrance faces along the sides carrying tabs 29 by reference numeral 21, while those having their entrance faces along the sides carrying tabs 28 by reference nu- Each dynode'is connected to a dynode sup- FIGS. and 10.-

mounting shoulders for the dynode structures 21 and 21'.

In the multiplier assembly, a multiplicity of dynode support plates 34, carrying their respective dynode structures, are stacked in cooperating pairs, as shown more particularly in FIGS. 2 and 10, with the recessed portions forming the dynode supporting shoulders of the dynode support plates of each pair directed inwardly toward each other. The dynode support plates are spaced from each other and are electrically insulated one from the other by means of electrically insulated members, such as Pyrex balls 39 which are held in position by means of seats formed by seating holes 40 provided at evenly spaced intervals adjacent the peripheries of the dynode supporting plates 34. Pump-out holes 41 directed radially inwardly from the edge perimeter of each plate 34 are provided to intersect seating holes 40 to allow the air trapped therein by balls 39 to escape when the vacuum envelope 1 is evacuated. Seating holes 42 are provided on the top surface of mounting plate 12 in alignment with seating holes 41 to provide seats for the insulating balls of the last dynode support plate in the multiplying chain.

The dynode structures are mounted in opposed relation on dynode support plates 34 of adjacent pairs of dynode support plates, as shown more particularly in FIG. 10. In each pair of dynode support plates one dynode structure is mounted to the recessed mounting flange 38 of one plate 34 such that a portion of the dynode extends through the aperture of the same plate 34 as well as the aperture 36 of the adjacent plate 34 of the cooperating pair of support plates 34. The other dynode structure is conneted to the recessed shoulder 37 of the last mentioned support plate 34 of the pair of support plates in a manner similar to the first dynode structure and in a position such that the concave curvatures of the dynode structures are directed inwardly toward each other. The dynode structures in the multiplier chain are thus arranged with respect to each other so that a beam of electrons can be consecutively directed from the concave portion'of one dynode to the concave portion of another dynode, etc., through the entire multiplier chain 'to the output collector of the device.

the measurement obtained at the output collector caused by the multiplication by secondary emission of stray electrons which might 'otherwise enter the channel. Each dynode structure is electrically connetced to a dynode support plate 34, and electrical connection is completed from each individual plate to an individual source of external potential by means of an electrical conductor such as the conductor 43 illustrated in FIGS. 5 and 11 connected to the edge perimeter of the dynode support plate by means of a screw 44 extending through a lug 45 connected to the end of conductor 43, the screw being threaded into a radial perimeter hole of the plate which is provided with an air pump-out hole 46 to enable any air trapped in the bottom of the threaded hole to be evacuated when the envelope 1 is subjected to vacuum. Internal resistors could also be used, thereby necessitating the use of only one potential lead. It will be noted that the

input lead housings

4, 5 and 6 are symmetrically arranged around the base of one half of the vacuum envelope 1 and the input leads 47, 43 and 48 extending respectively through these input housings then extend into electrical connection with the various members as described. The electrical leads are connected to the perimeters of the dynode support plates at positions substantially in alignment with the

input housings

4, 5 and 6, such that the input leads 47 to every third plate member 34 extends through housing 4, the input leads 43 to every other third plate member extends through housing 5 and the input leads 48 for the remaining plate members extend through the housing 6. With this manner of connecting the electrical leads to the individual plate members less congestion is caused within the tube to increase the ease of disassembling the tube.

An individual potential is provided on each of the wires leading to the dynode support plates, such that the potential charge on each plate starting with the plate nearest the entrance of the ion beam is progressively more positive progressing toward the last plate in the dynode chain. Thus, there is a potential difference between consecutive dynode structures, and for purposes of illustration, normally a charge of approximately 4000 volts is applied to the first dynode structure which receives the ion beam and the charges applied to the other structures become progressively more positive to a charge of approximately (0) zero volts on the last dynode structure in the multiplier channel.

A repeller electrode 49 having an aperture therein of a size to register with the opening of the first dynode structure in the multiplier channel is positioned by means of insulation balls 39 in front of the first dynode, as shown particularly in FIG. 2. This repelicr electrode is provided to optimize the electron orbits from the first dynode to the second dynode. This optimization is accomplised by field penetration into the first dynode. The repeller adjustment is important because there are no grid wires on the first dynode.

A shield electrode 50, having a slightly negative charge thereon brought in by an electrical lead 48, and having an aperture in registration with the aperture of repeller electrode 49 is positioned in front of the repeller electrode and spaced therefrom by means of large Pyrex insulation balls 51. Shield electrode 59 and repeller electrode 49 are of the same general configuration as shown in FIG. 4 and have the function of reducing field penetration from region 52-49 and hence makes optimum adjustment of repeller 49 independent of multiplier voltage. This does not mean that the voltage difference E -50 is zero, but that it is a constant fraction which could well be one half of the total electron multiplier voltage. As with the plates 34 the seating holes for insulating balls 51 are air-relieved.

A large flange 52, provided with a central aperture larger than the apertures of

electrodes

49 and 50, as particularly illustrated in FIGS. 2 and 3, is positioned forwardly of shield electrode 50 and spaced therefrom by means of insulation balls 51 which are provided with the usual seating holes 53 positioned inwardly of the perimeter of the flange. Assembly bolt holes are provided at 93 intervals, or other convenient spacing, adjacent the perimeter of flange 52 and mounting rods 54- extend therethrough and outwardly of the peripheries of the plurality of dynode support plates, and into screw-threaded en gagernent with corresponding holes in top mounting plate 12 of the mounting flange assembly. The rods 54 are constructed of Inconel metal or the like and since

mem bers

2, 3, and 12 are at ground potential, repeller flange 52 is also connected at ground potential through the Inconel mounting rods 54. Thus the entire assembly is secured together by these mounting rods and in order to disassemble the multiplier device of the invention for cleaning and replacement of component parts, it is merely necessary to remove the four mounting rods 54, the repeller flange 52 and its insulating balls 51, and then removing the remainder of the components, a member at a time, together with their corresponding ball separators, until the entire multiplier assembly is completely disassembled. It will, of course, be necessary during the progress of disassembling the device to disconnect the electrical leads connected with the individual flange and

plate members

30, 49 and 34.

As more particularly shown in FIGS. 2 and 6, a collector member 55 is positioned adjacent the output of the last dynode structure in the multiplier chain so that all of the output electrons emanating from the device can be collected on this member. The collector 55 is electrically connected to output lead 17, extending to insulation lead-through member 15 by means of conductor 56. As shown more particularly in FIG. 2, the back portion of the last dynode in the channel is electrically connected to output lead 18 by means of conductor 57, which can be spot-welded, or the like, to the dynode. By means of a switch (not shown) exteriorly of the tube, either

output lead

17 or 18 may be utilized. When output lead 17 is utilized, the electron stream from the last dynode is collected on collector 55, whereas, when output lead 18 is used in lieu of lead 17, the output stream of electrons is collected directly from the last dynode structure through conductor d7. Both outputs 1'7 and 18 may be used simultaneously with the phase of the signal being opposite on the two collectors. Alternatively, plate 18 alone can be used and the phase of the signal reversed depending on whether plate 17 is or with respect to it. Both plates used at once means DC. output on 17 and simultaneous pulse counting on 18.

The ion beam 7, emanating from the vacuum system, passes through the repeller flange 52, the shield electrode 5% and the repeller electrode 49. At this point the positive ion beam enters the first dynode structure, and strikes the negatively charged concave surface of the first dynode 21' which produces secondary electrons, and due to the ne ative charge on the surface then ejects them toward the next dynode structure. The next dynode structure 21 is at a less negative potential than the first dynode structure and thus attracts the secondary electrons. The secondary electrons are accelerated as they pass through the wires 33 of the second dynode 21 and are attracted to strike the concave surface of the second dynode to produce a multiplied number of additional secondary electrons thus multiplying the current. As before, the negative charge of the dynode repels or rejects all of the secondary electrons toward the third dynode in the chain and the electron stream is again accelerated as it passes through the again less negative Wires of the third dynode and as it strikes the concave surface of the third dynode structure the electron stream is again multiplied by the phenomenon of secondary emission. This process continues through the dynode channel as indicated by the dotted line 7, in FIG. 2, with each succeeding dynode being less negatively charged than the preceding one to progress the electron stream through the channel. As previously stated, the construction of the dynode support plates 34 from a high permeability alloy provides magnetic shielding for the dynode channel and the multiplier structure itself. As previously stated, the output current from the dynode multiplier channel may be selectively taken either directly from the surface of the last dynode or from a collector 55 positioned adjacent the exit of the last dynode. The output lead, either 17 or 18, is connected to the proper electronic measuring device exteriorly of the vacuum envelope to render an indication of the multiplied electron beam collected.

While I have described my invention in one of its enibodiments, I realize that modifications can be made, and I desire that it be understood that no limitations upon the invention are intended other than may be imposed by the scope of the appended claims.

. 7 V What I claim as new and desire to secure by Letters Patent of the United States, is as follows 1. A multiplier device for multiplying a stream of electrons comprising, an evacuated envelope, base structure means for said device, a plurality of apertured dynode support elements mounted on said base structure means,

electron repeller electrode means mounted in front of said plurality of apertured dynode support elements, repeller mounting flange means mounted in front of said electron repeller electrode means, said base structure means, plurality of apertured dynode support elements, electron repeller electrode means and repeller mounting flange means each being electrically isolated and spaced from each other by readily removable electrical insulating means, a plurality of pie-type dynode elements respectively carried by said plurality of apertured dynode support elements, said plurality of dynode elements being fastened in the apertures of said support elements and positioned to serially pass an electron stream therethrough, output collector means supported by said base structure means and positioned adjacent said dynode elements and readily removable assembly securing means extending intermediate said repeller mounting flange meansand said base structure means for mounting said electrodes and support elements to said base structure means through said removable insulating means and rendering said device to be easily and completely disassembled.

2. A multiplier device as set forth in claim 1, in which said dynode support elements are constructed of a high permeability material to provide magnetic shielding for the multiplying channel formed by the plurality of pietype dynode elements.

3. A multiplier device as set forth in claim 1, in which said plurality of pie-type dynode elements individually carry accelerating means across the open faces thereof.

4. A multiplier device as set forth in claim 1, in which said plurality of pie-type dynode elements form an eletcron multiplying channel and individually carry a plurality of charged accelerating wires across their open face,

5. A multiplier device as set forth in claim 1, in which said plurality of dynode elements form a multiplying channel having an input and output, and said repeller mounting flange means and said electron repeller electrode means carry centrally disposed apertures in registration with the input of the multiplying channel.

6. A multiplier device as set forth in claim 1, in which said readily removable assembly securing means comprise threaded elongated mounting bolts.

7. A multiplier device as set forth in claim 1, in which said readily removable assembly securing means are spaced substantially outwardly of the perimeters of said electron repeller electrode means and said plurality of dynode support elements for rendering the assembling and disassembling of the device less cumbersome.

8. A multiplier device as set forth in claim 1, including external potential means, and individual means connecting said electron repeller electrode means and said plurality of dynode support elements to said external potential 8 means for providing an individual potential to each of said members.

9. A multiplier device as set forth in claim 1, in which said plurality of dynode elements constitute a multiplying channel having an input dynode and an output dynode, an output conductor secured to the output dynode, said output conductor being selectively operable to convey the output of the multiplying channel from the output dynode in lieu of said output collector means.

10. A dynode evolved from a blank of sheet material for use in an electron multiplier device, said blank comprising a main body portion, side extension members connected with the lower portion of said main body portion and extending outwardly therefrom, arcuate edge portions carried by said side extension members rearwardly of said main body portion, apertured extensions connected to said arcuate edge portions and extending inwardly towards each other in parallel relation.

11. A blank for evolving a dynode as set forth in claim 19, in which the base of said main body portion, said side extension members, and said apertured extensions define a T-shaped opening.

12. A blank for evolving a dynode as set forth in claim 10, and tab elements connected to the sides of said main body portion adjacent the top edge and extending outwardly therefrom.

13. A blank for evolving a dynode as set forth in claim 10, in which said main body portion is generally rectangular in shape.

14. A blank for evolving a dynode as set forth in claim 10, in which said blank is foldable along lines across the junction of said main body portion and said side extension members, and a line across said main body portion at a position in alignment with the forward portion of said side extensions, and said main body portion is adapted to be curved along the arcuate edge portions to evolve a substantially hollow quarter cylinder structure having closed ends.

15. A blank for evolving a dynode as set forth in claim 10, in which tab extensions are carried by the edges of said side extension members other than said arcuate edge portions to render a notched appearance to the edges.

16. A blank for evolving a dynode as set forth in claim 10 in which said blank is constructed of a material which will give secondary electron emission.

17. A blank for evolving a dynode as set forth in claim 10 in which said blank is constructed of a beryllium copper alloy.

References Cited by the Examiner UNITED STATES PATENTS 2,231,692 2/ 1941 Snyder 313- 2,433,821 12/1947 Toorks 313346 2,653,268 9/1953 Kumpfer 313-346 2,824,253 2/1958 Pong et al 313105 GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, Examiner.

Claims

10. A DYNODE EVOLVED FROM A BLANK OF SHEET MATERIAL FOR USE IN AN ELECTRON MULTIPLIER DEVICE, SAID BLANK COMPRISING A MAIN BODY PORTION, SIDE EXTENSION MEMBERS CONNECTED WITH THE LOWER PORTION OF SAID MAIN BODY PORTION AND EXTENDING OUTWARDLY THEREFROM, ARCUATE EDGE PORTIONS CARRIED BY SAID SAID EXTENSION MEMBERS REARWARDLY OF SAID MAIN BODY PORTION, APERTURED EXTENSIONS CONNECTED TO SAID ARCUATE EDGE PORTIONS AND EXTENDING INWARDLY TOWARDS EACH OTHER IN PARALLEL RELATION.