US3634713A - Electron multiplier having means for altering the equipotentials of the emissive surface to direct electrons towards the anode - Google Patents

Electron multiplier having means for altering the equipotentials of the emissive surface to direct electrons towards the anode Download PDF

Info

Publication number
US3634713A
US3634713A US855889A US3634713DA US3634713A US 3634713 A US3634713 A US 3634713A US 855889 A US855889 A US 855889A US 3634713D A US3634713D A US 3634713DA US 3634713 A US3634713 A US 3634713A
Authority
US
United States
Prior art keywords
emissive
combination
recited
emissive surface
conducting paths
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US855889A
Other languages
English (en)
Inventor
Theodore Foote
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bendix Corp
Original Assignee
Bendix Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bendix Corp filed Critical Bendix Corp
Application granted granted Critical
Publication of US3634713A publication Critical patent/US3634713A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
    • H01J43/04—Electron multipliers
    • H01J43/06—Electrode arrangements
    • H01J43/14—Control of electron beam by magnetic field
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/025—Detectors specially adapted to particle spectrometers

Definitions

  • a plurality of electron conducting paths are arranged in a pattern along the sides of the emissive surface of an electron multiplier to cause emitted electrons to travel towards the anode along a path defined by the sides of the emissive surface.
  • FIGURE 2 FIGURE 3
  • FIGURE 5 ATTORNEY ELECTRON MULTIPLIER HAVING MEANS FOR ALTERING THE EQUIPOTENTIALS OF THE EMISSIVE SURFACE TO DIRECT ELECTRONS TOWARDS THE ANODE BACKGROUND
  • This invention relates to electron multipliers and more specifically to a magnetic electron multiplier of the type having a source of primary electrons, an electron emissive surface having a secondary emission ratio greater than 1, and an anode or collector for detecting the electrons generated by the source of primary electrons and the secondary electron emissive surface.
  • the electron multiplier is useful for general amplification purposes and for photomultiplication, its usefulness for particle detection, such as in mass spectrometry, has created the need for a high resolution electron multiplier.
  • baffle that was located perpendicular to and surrounding the reverse side of the emissive surface.
  • a baffle is structurally undesireable as its location and size is limited to the space available around the emissive surface and, although the baffle does stop escaped electrons from returning to the source of primary electrons, it does nothing to prevent electrons from escaping the path defined by the outer edges of the emissive surface.
  • the present invention substantially all the electrons traveling from an electron emissive surface towards an anode are confined to a path defined by the edges of the emissive surface. This is accomplished by arranging a plurality of electron conducting paths on the emissive surface so that when a potential is applied to the surface the potential gradient along the surface is shaped in a manner that causes at least a portion of the equipotentials of the potential gradient to assume a curved shape.
  • the electron conducting paths may be comprised of a family of lines or curvilinear paths extending from the sides of the emissive surface.
  • each line is characterized by the fact that all or substantially all of the line is not in a direction perpendicular to any side of the emissive surface and that a substantial portion of each line is further from the anode than the point where the line meets the side (edge) of the emissive surface.
  • the lines themselves are characterized by the fact that the material which comprises the lines is a much better conductor than the emissive surface and in most instances has a resistance less than 1/ l ,000 of the resistance of the emissive surface.
  • lt is another object of this invention to establish a potential gradient along an emissive surface wherein the equipotentials of the gradient along a portion of the surface are shaped to cause electrons emitted from said surface to range within the path defined by the edges of the emissive surface.
  • FIG. 1 is a partial diagrammatic side view of a magnetic electron multiplier illustrating the cycloidal path of electrons traveling between the plates of the multiplier of the anode.
  • FIG. 2 is a plan view of one of the plates of the electron multiplier showing one arrangement of conducting lines located on the surface of that plate.
  • FIG. 3 is an arrangement showing conducting lines that travel from one edge of an electron-emitting surface to another.
  • FIG. 4 is an arrangement of curvilinear lines located on an emissive surface.
  • FIG. 5 indicates the shape of the equipotentials when a potential is applied to the emissive surface shown in FIG. 2.
  • FIG. I shows a portion of a magnetic electron multiplier (e.g. U.S. Pat. No. 2,841,729 or 2,983,845) having a source of primary electrons 10, a pair of parallel plates 20, 40, and a collector or anode 30 for detect ing secondary electrons.
  • the source of primary electrons 10 may be a cathode which emits electrons when impinged by ions and is positioned to introduce electrons onto one of the parallel plates 20,40.
  • the cathode is maintained at a higher negative potential (e.g., 3,200 volts) than the plates 20, 40.
  • the plates 20, 40 are spaced from each other at a distance of approximately one-fourth inch, and a pair of pole pieces (not shown) are disposed adjacent the plates 20, 40 to provide a magnetic field in the region between the plates that is substantially parallel to their inner surfaces.
  • the plates 20, 40 are provided with a conductive strip or coating 21, 41 on their inner surface.
  • the coatings 21, 41 are comprised of a secondary electron emissive material such as a tin oxide or a carbon compound which has a relatively high resistance and a secondary electron emission ratio greater than 1.
  • the emissive coating 41 on plate 40 may be made from a material which has a relatively high resistance but which does not have the secondary emissive qualities required for coating 21.
  • the plates 20, 40 themselves are made of insulating or nonconducting material such as glass or bakelite. Terminals 24, 25 are provided on the opposite ends of the plate 20 to receive a potential for the conductive strip 21. Similarly, terminals 42, 45 are provided on the op posite ends of plate 40.
  • Different combinations of voltages may be applied to the terminals 23, 25, 43, 45 by power supply 5 to achieve different results, e.g., perpendicular or slanting electric fields between the plates 20, 40 but essential to the proper operation of the electron multiplier is a potential applied to terminals 23, 25.
  • a direct negative potential less than that applied to the cathode such as -3,000 volts, is applied across terminals 23, 25 with terminal 25 being at ground potential. This establishes a negative potential gradient along the emissive surface 21 which decreases as it approaches the anode 30.
  • the anode plate 30 is preferably disposed in a substantially perpendicular relationship to the plate 20, 40 to receive electrons produced by secondary emission from the surface 23.
  • the anode 30 may be connected to a source of positive potential (e.g., +1 ,500 volts) to attract the electrons emitted from the surface 21.
  • electrons emitted by the cathode are subjected to the combined action of the magnetic and electric field between the plates and 40. This causes the electrons to travel in a cycloidal path 50 and to strike the emissive surface 21 which emits a proportionately increased number of electrons.
  • the electrons emitted from the surface 21 travel in a cycloidal path 52 and impinge upon another part of the surface 21 to again emit a proportionately increased number of electrons for cycloidal travel to another part of the emissive surface 21.
  • successively emitted electrons travel across the surface 21 in successive cycloidal paths to multiply the number of electrons initially emitted by the cathode 10.
  • the electrons emitted from the end of the surface 21 impinge upon the anode 30 for detection.
  • FIG. 2 shows the emissive surface 21 with the preferred arrangement of conducting lines 22 to accomplish the purposes of this invention.
  • the conducting lines 22 may be on the surface of the plate 20 but preferably the plate 20 is first coated with an electron emissive material 21 such as tin oxide and then a plurality of electron conducting paths 22, having a resistance less than the emissive surface 21 is located (e.g., by sputtering) on the emissive surface 21.
  • the resistance of the conducting paths 22 are in the order of 1/l,OOO to l/ l ,0O0,000 or less than the resistance of the surface 21 and are comprised of a conductive material such as chromium, copper, gold platinum or stainless steel deposited as a thin film on the emissive surface 21.
  • the thin film of conducting material 22 may be applied by any conventional means such as spraying, sputtering, painting or vaporizing.
  • the direction of the conducting paths shown is such that each line, when viewed from the anode, makes an acute angle A with the sides (C,D) of surface 21, having sides C and D.
  • each line has a direction which intersects side C, D, of the emissive surface and the plane in which the anode is located at an acute angle.
  • Shown also on the surface are the terminals 23, to which a negative potential is applied to establish a gradient (not shown) along the length of the surface 21.
  • the gradient is a series of negative equipotentials (imaginary parallel lines) decreasing in magnitude from one to another in the direction of the anode (when a higher negative potential is applied to terminal 23 than terminal 25).
  • Power supply 5 supplies the potentials to properly bias the anode and the emissive surface 21 between terminals 23, 25.
  • the preferred relationship of the conducting paths 22 to the anode and cathode is such that the conducting paths extend on the emissive surface 21, away from the sides (C, D) of the plate 20 and travel in a direction away from the anode 30 and towards the cathode 10. Also, the conducting paths 22 are arranged in parallel relationship along the sides of the surface and although it is not necessary for each line 22 to extend completely across the surface 21, it is preferable to have the conducting paths extend to one edge (C or D) ofthe surface 21.
  • FIG. 3 is an alternate pattern of conducting paths 22 arranged in a parallel relationship.
  • Each conducting path 22 extends from one edge (C) to the emissive surface 21 to the other edge (D) and may be considered as being comprised of at least two straight lines that intersect at an angle on the surface.
  • the surface shown is rectangular in shape to conform to the shape of the plate 20.
  • the conducting paths are arranged to cause equipotentials to shape themselves such that the apex 27 of each equipotential is in a direction ofa greater negative potential. This arrangement causes an electron moving over the surface to seek a path towards the longitudinal axis of the emissive surface.
  • FIG. 4 shows a series of conducting paths 22 which are curvilinear in shape. Each path is arranged so that the concave or hollow portion 29 of each peak of an equipotential faces a direction of a lower potential (decreasing negative or increasing positive) to cause an electron moving over the surface 21 towards an edge (C or D) to be attracted away from an edge (C or D) and towards the anode 30.
  • FIG. 5 shows the shape of the equipotentials when a potential is applied to the multiplying surface shown in FIG. 2.
  • a direct negative potential is applied to terminals 23, 25 with terminal 23 being at a higher negative potential than terminal 25.
  • This establishes a potential gradient along the longitudinal axis 60 of the emissive surface 21.
  • the equipotentials 61 which would normally be a series of straight lines each perpendicular to both sides. C, D, of the surface 21, are distorted by the conducting paths so that a portion 63 of the equipotential 61 is curved.
  • the fact that the equipotentials are not straight lines creates a second potential gradient on the emissive surface 21 along a line perpendicular to the axis 60 of the first potential gradient.
  • the second potential gradient along line 70 is characterized by the fact that the negative potential along line 70 decreases in magnitude when approaching the longitudinal axis 60 of the first gradient.
  • each line 22 terminated away from the edges (CD) of the emissive surface 21 and the other end extended to one edge (C or D) of the surface 21.
  • Each line 22 extended approximately one-sixth of the distance across the surface at an angle of 45 (angle A), and because the plate and emissive surface were rectangular in shape, each of the lines 22 had a direction that was not perpendicular to any side of the emissive surface 21 (rectangle C, D, E, F).
  • the second potential gradient created by the conducting paths 22 subjects the electrons to an electric field that changes the direction of the velocity vector of the electrons away from the edge (C or D) of the surface 21. This confines substantially all the electrons leaving the emissive surface 21 to the path defined by the sides (C, D) of the surface.
  • the shape of the emissive surface 21 is rectangular to conform to the shape of the plate 20, however, the shape of the emissive surface and the arrangement of the conducting paths may assume any configuration that would prevent the escape of electrons from the surface. Accordingly, it is intended that the illustrative and descriptive materials employed herein be used to illustrate the principles of the invention and not to limit the scope thereof.
  • a magnetic electron multiplier comprising:
  • a secondary electron emissive means for producing secondary electrons upon impact of primary electrons, said emissive means including a substrate having a first and second end, with a longitudinal axis therebetween, a resistive secondary electron emissive material disposed on one surface thereof, and a plurality of electron conducting paths, disposed on aid emissive surface in spaced relationship to each other, each of said paths extending in a direction generally transverse of said longitudinal axis and having at least a portion of said path extending in a direction towards the first end of said substrate;
  • anode means disposed at said second end of said substrate for collecting secondary electrons leaving the second end of said substrate.
  • each of said conducting paths comprises at least two straight lines that intersect at an angle.
  • said emissive surface is rectangular in shape and wherein said conducting paths are straight lines arranged in a parallel relationship to each other along at least one side of said rectangle, each of said lines having a direction which is not perpendicular to any side of said rectangle.
  • the material comprising the conducting path is selected from the group consisting of chromium, copper, gold, platinum or stainless steel.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Cold Cathode And The Manufacture (AREA)
  • Magnetic Heads (AREA)
US855889A 1969-09-08 1969-09-08 Electron multiplier having means for altering the equipotentials of the emissive surface to direct electrons towards the anode Expired - Lifetime US3634713A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US85588969A 1969-09-08 1969-09-08

Publications (1)

Publication Number Publication Date
US3634713A true US3634713A (en) 1972-01-11

Family

ID=25322352

Family Applications (1)

Application Number Title Priority Date Filing Date
US855889A Expired - Lifetime US3634713A (en) 1969-09-08 1969-09-08 Electron multiplier having means for altering the equipotentials of the emissive surface to direct electrons towards the anode

Country Status (4)

Country Link
US (1) US3634713A (de)
DE (1) DE2031115A1 (de)
FR (1) FR2060549A5 (de)
GB (1) GB1322257A (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3936687A (en) * 1971-03-01 1976-02-03 U.S. Philips Corporation Photocathode with plurality of concentric conducting rings
US5117149A (en) * 1990-05-09 1992-05-26 Galileo Electro-Optics Corporation Parallel plate electron multiplier with negatively charged focussing strips and method of operation
US20030205956A1 (en) * 2002-05-03 2003-11-06 Downing R. Gregory Electron multipliers and radiation detectors
US20050205798A1 (en) * 2004-03-01 2005-09-22 Downing R G Radiation detectors and methods of detecting radiation
US7183701B2 (en) 2003-05-29 2007-02-27 Nova Scientific, Inc. Electron multipliers and radiation detectors
US20100044822A1 (en) * 2006-12-06 2010-02-25 Politecnico Di Milano Luminous radiation colour photosensitive structure
US10262846B2 (en) * 2015-07-29 2019-04-16 ETP Ion Detect Pty Ltd Apparatus and methods for focussing electrons

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2668184A (en) * 1952-02-15 1954-02-02 Gen Electric Multiple photocell structure
US2705764A (en) * 1950-02-25 1955-04-05 Rca Corp Dual-area target electrodes and methods of making the same
US2932768A (en) * 1955-10-21 1960-04-12 Bendix Aviat Corp Magnetic electron multiplier
US3321660A (en) * 1962-05-24 1967-05-23 Rca Corp Electron multiplier having resistive secondary emissive surface which is adapted to sustain a potential gradient, whereby successive multiplication is possible

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2705764A (en) * 1950-02-25 1955-04-05 Rca Corp Dual-area target electrodes and methods of making the same
US2668184A (en) * 1952-02-15 1954-02-02 Gen Electric Multiple photocell structure
US2932768A (en) * 1955-10-21 1960-04-12 Bendix Aviat Corp Magnetic electron multiplier
US3321660A (en) * 1962-05-24 1967-05-23 Rca Corp Electron multiplier having resistive secondary emissive surface which is adapted to sustain a potential gradient, whereby successive multiplication is possible

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3936687A (en) * 1971-03-01 1976-02-03 U.S. Philips Corporation Photocathode with plurality of concentric conducting rings
US5117149A (en) * 1990-05-09 1992-05-26 Galileo Electro-Optics Corporation Parallel plate electron multiplier with negatively charged focussing strips and method of operation
US20030205956A1 (en) * 2002-05-03 2003-11-06 Downing R. Gregory Electron multipliers and radiation detectors
US6828714B2 (en) * 2002-05-03 2004-12-07 Nova Scientific, Inc. Electron multipliers and radiation detectors
US20050093410A1 (en) * 2002-05-03 2005-05-05 Nova Scientific, Inc., A Massachusetts Corporation Electron multipliers and radiation detectors
US7394187B2 (en) 2002-05-03 2008-07-01 Nova Scientific, Inc. Electron multipliers and radiation detectors
US7990032B2 (en) 2003-05-29 2011-08-02 Nova Scientific, Inc. Electron multipliers and microchannel plates
US8221181B2 (en) 2003-05-29 2012-07-17 Nova Scientific, Inc. Electron multipliers and microchannel plates
US7183701B2 (en) 2003-05-29 2007-02-27 Nova Scientific, Inc. Electron multipliers and radiation detectors
US20070132351A1 (en) * 2003-05-29 2007-06-14 Nova Scientific, Inc. Electron multipliers and radiation detectors
US7508131B2 (en) 2003-05-29 2009-03-24 Nova Scientific, Inc. Electron multipliers and radiation detectors
US20090179542A1 (en) * 2003-05-29 2009-07-16 Downing R Gregory Electron Multipliers and Radiation Detectors
US7233007B2 (en) 2004-03-01 2007-06-19 Nova Scientific, Inc. Radiation detectors and methods of detecting radiation
US20050205798A1 (en) * 2004-03-01 2005-09-22 Downing R G Radiation detectors and methods of detecting radiation
US20100044822A1 (en) * 2006-12-06 2010-02-25 Politecnico Di Milano Luminous radiation colour photosensitive structure
US10262846B2 (en) * 2015-07-29 2019-04-16 ETP Ion Detect Pty Ltd Apparatus and methods for focussing electrons

Also Published As

Publication number Publication date
GB1322257A (en) 1973-07-04
DE2031115A1 (de) 1971-03-11
FR2060549A5 (de) 1971-06-18

Similar Documents

Publication Publication Date Title
US3128408A (en) Electron multiplier
Goodrich et al. Resistance strip magnetic electron multiplier
US2841729A (en) Magnetic electron multiplier
US20060231769A1 (en) Particle detection by electron multiplication
US2853641A (en) Electron beam and wave energy interaction device
US3634713A (en) Electron multiplier having means for altering the equipotentials of the emissive surface to direct electrons towards the anode
US3673457A (en) High gain storage target
US3172004A (en) Depressed collector operation of electron beam device
US6982428B2 (en) Particle detection by electron multiplication
US2774913A (en) Electron discharge tube with crossed electric and magnetic fields
US3235765A (en) Electron multiplier having an inclined field
US2147756A (en) Secondary electron tube
US2807739A (en) Devices of focusing of electronic beams
US2237671A (en) Electron discharge device
US2983842A (en) Electrode system
US4227116A (en) Zero-bias gridded gun
US5117149A (en) Parallel plate electron multiplier with negatively charged focussing strips and method of operation
US2983845A (en) Electron multiplier spurious noise baffle
US2841741A (en) Multi-anode high speed switching tube
GB2090051A (en) Method and apparatus for controlling electrode voltage in electron beam tubes
US3225239A (en) Electron multiplier
US3278751A (en) Parallel plate electron multiplier having an inclined electric field and operative without a magnetic field
US4155028A (en) Electrostatic deflection system for extending emitter life
US1659636A (en) Device fob amplifying voltage and cubeent
US4321505A (en) Zero-bias gridded gun