US2231682A - Electron multiplier - Google Patents

Electron multiplier Download PDF

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Publication number
US2231682A
US2231682A US171916A US17191637A US2231682A US 2231682 A US2231682 A US 2231682A US 171916 A US171916 A US 171916A US 17191637 A US17191637 A US 17191637A US 2231682 A US2231682 A US 2231682A
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US
United States
Prior art keywords
electrode
electrodes
cathode
electron
multiplying
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
US171916A
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English (en)
Inventor
Jan A Rajchman
Eugene W Pike
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RCA Corp
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RCA 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
Priority to BE430852D priority Critical patent/BE430852A/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US177286A priority patent/US2231691A/en
Priority to US171916A priority patent/US2231682A/en
Priority to NL90376A priority patent/NL57028C/xx
Priority to FR845191D priority patent/FR845191A/fr
Priority to GB31156/38A priority patent/GB520117A/en
Priority to CH206023D priority patent/CH206023A/de
Application granted granted Critical
Publication of US2231682A publication Critical patent/US2231682A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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
    • H01J43/18—Electrode arrangements using essentially more than one dynode
    • H01J43/20—Dynodes consisting of sheet material, e.g. plane, bent

Definitions

  • This invention relates to electron multipliers (i. e., electron discharge tubes of the type wherein amplification of a primary electron stream, such, for example, as is emitted by a thermionic cathode or by a photosensitive surface exposed to light, is accomplished through utilization of the phenomenon of secondary emission), and has special reference to the provision of improvementsin electron multipliers of the type operable without the use of auxiliary electron-lens systems.
  • Discharge tubes of the class to which the invention particularly relates are well exemplified in copending applications Serial No. 107,955 and Serial No. 144,825 of Edward G, Ramberg.
  • Ramberg by providing a tube having electrodes of a novel design and arrangement, and maintained at definite potentials, obviates the above described and certain other disadvantages inherent in electrostatically controlled electronmultipliers of the prior art.
  • One trouble, however, encountered in the operation of the Ramberg electron multiplier is that when the electron stream has been increased by several stages of electron multiplication, positive ions may be generated. This phenomenon has been observed to exist even in the most thoroughly evacuated multi-stage tubes. These positively charged particles flow in a direction opposite to the general direction of the electron stream and may im-. pinge upon the primary-electron emitting cathode, or upon an intermediate secondary-electron emitter where they release still more electrons.
  • the electron current may thus be augmented to such a degree as to render it uncontrollable.
  • This building up of the electron current is limited only by the so-called space charge effect and may result in an equilibrium of the output current, i. e., the output current may no longer accurately reflect variations in the input current.
  • a principal object of the present invention is to provide an improved electron multiplier wherein the output current is directly proportionalto the input current and this, too, substantially irrespective of the intensity of the electron stream impinging upon the outputelectrode.
  • Another and important object of the present invention is to provide an electron multiplier wherein ions generated in the residual gas by the passage of the electron beam are entrapped and dissipated by barriers near their area of origin. 10
  • Another object of the invention is to provide an electron multiplier wherein, by reason of a novel design and relative arrangement of the electrodes, the electric fields adjacent the multiplying electrodes will exhibit a greater intensity, 15 causing saturation and hence optimum effective emission of secondary electrons.
  • Another object of the invention is to provide an electron multiplier wherein the space charge effect and spreading of the electron beam is less :20 pronounced than in analogous prior art devices.
  • Still another object of this invention is to provide an electron multiplier wherein dark current (current which flows when the tube is energized but the cathode not illuminated) is minimized.
  • Figure 1 is a partly diagrammatic longitudinal sectional view of an electron multiplier constructed in accordance with the principle of the invention and exemplifying the manner in which 35 the several electrodes are energized when the device is utilized for certain of the purposes to which it is adapted, and
  • Figure 2 is a longitudinal sectional view of an electron multiplier showing an electron multio plier having electrodes of an alternative construction.
  • Fig. 1 shows a highly evacuated envelope T, 5 which is preferably, though not necessarily, in the form of a cylindrical glass tube having a long central axis indicated in the drawing by dotted line xa:.
  • Line xa: may comprise an axis of symmetry of the tube or envelope T; the herein 50 described electrode structure, however, has neither an axis nor a plane of symmetry.
  • Tube T contains a pair of terminal electrodes of a con tour later described, suitably mounted at opposite ends of this axis and comprising a photosensitive cathode I and an anode or collector electrode II.
  • Electrodes 2 to H1, inclusive may be formed, for example, of silver suitably coated with a substance which is the equivalent of caesium, to render them capable of emitting a copious flow of secondary electrons.
  • the distance measured between a point on one multiplying electrode to a corresponding point on the next adjacent electrode in the same set should be less than the distance be- Excellent performance has been achieved in a tube wherein
  • the long legs m (they are so designated in both figures) of the L-shaped multiplying electrodes are inclined toward the cathode, and the free or terminal edges of these long legs preferably extend to (or, in the case of Fig. 2, beyond) equally spaced points m along the central axis :ra:.
  • the axis a:-a comprises the -median line of the electron path which extends between the cathode and anode.
  • each L-shaped multiplying electrode say electrode 8, Fig. 1
  • the long leg m of each L-shaped multiplying electrode say electrode 8, Fig. 1
  • the long leg of each L extends beyond the short leg n of the next preceding L of the same (say, the upper) set.
  • the terminal electrodes 1. e., the primary electron emitting cathode I and the collecting electrode or anode II, are of a contour such as to ensure a desired distribution of the electrostatic field adjacent these electrodes when the device is energized.
  • the illustrated modified L- shape contour of electrodes I and II corresponds to the contour of the equipotential surface which would be present midway, electrically, between two adjacent multiplying electrodes (in the same upper or lower set) in a'device having an infinite number of multiplying electrodes.
  • the particular forms of theelectrode plates I and I I of the illustrated embodiments of the invention were determined by constructing 55 a scale model in' metal of the electrodes 2 to I0,
  • Section lm of the cathode is of foraminous construction to permit light from an external source, exemplified in Fig. 1 by the lamp Y and lens Z, to impinge upon the photosensitive surface of the cathode section In.
  • the long section IIm of the anode is preferably ofimperforate construction; it is upon this portion of the anode that the secondary electrons are collected.
  • the potential distribution required to ensure optimum performance may be expressed by the mathematical series IV, 2V, 3V, 4V, 5V, 6V, etc., where IV is the potential drop between the primaryelectron source and the first target or multiplying electrode, and 2V, 3V, 4V, etc., represent the potential drop between the respective succeeding electrodes, in point of electron travel, and said source.
  • the cathode I may be connected to the negative terminal V of a. direct current source, exemplified in the drawing by a resistor R, and the first multiplying electrode, i. e., electrode 2, connected to a point IV somewhat more positive.
  • the other electrodes 3 to II, inclusive, in the order of their numbers, are shown connected to successively more positive points 2V to IOV on the resistor.
  • the reference characters IV, 2V, 3V, 4V, etc., given to the several points on resistor R, will be understood to indicate that the voltage drop between a given electrode and the cathode is the designated whole number multiple of the drop existing between the cathode I and the first multiplying electrode 2.
  • the drop between electrodes 3 and I should preferably be 200 volts, that between electrodes 4 and I, 300 volts.
  • photo-electrons will be emitted in a quantity determined by the instantaneous intensity of the light beam. 'I'hese photo-electrons will be accelerated toward the first upper" electrode 2 and, because of the described design, relaive arrangement, and voltage distribution, will impinge upon this first multiplying electrode.
  • the photo-electrons striking electrode 2 will cause the emission of secondary electrons, the number of secondary electrons emit-ted being dependent, in part at least, upon the magnitude of the potential between it and the'cathode.
  • the next electrode in point of electron travel is the second lower electrode 3.
  • the trajectory of secondary electrons from the first multiplying electrode 2 is such that they impinge upon the cupped surface of the second multiplying electrode 3.
  • a multiplication by reason of secondary emission, is secured and this is repeated in any numberof stages until the amplified stream of secondary electrons is collected upon the tilted long leg lIm of the output electrode I I and caused to flow in a utilization circuit exemplified in the drawing by the resistor 1" included between the output electrode II and the positive terminal IDV of the potential divider.
  • ions generated in the space between the last multiplying electrode Ill and the anode II will be collected by the long legs m of electrodes 9 and ID. This prevents internal feed-back and provides a tube having a more nearly linear response, greater stability, and smaller dark current (i. e., current which flows when the multiplier is energized but the cathode not illuminated).
  • the electrodes be of the cupped or curved L-shape construction shown in Fig. 1.
  • they may, for example, comprise long and short plane surfaces m and n, respectively, joined at substantially right angles to each other.
  • An electric discharge device comprising an evacuated envelope containing a cathode, an anode and a plurality of sets of substantially L- shaped multiplying electrodes mounted on opposite sides of the median line which spans the space between said cathode and anode, the long legs of said Ls extending from said median line with their free ends inclined toward the cathode and the short legs of said US extending in the direction of the anode and terminating at points spaced from said median line.
  • An electric discharge device comprising an evacuated envelope having a long axis, a plural-. ity of sets of multiplying electrodes mounted in staggered relation on opposite sides of said axis, said electrode sets comprising an assembly having neither an axis nor a plane of symmetry, a cathode and an anode substantially enclosing opposite endsof said electrode assembly, said cathode and anode each having a contour which corresponds to the contour of the equipotential surface which would be present midway, electrically, between two adjacent multiplying electrodes of the same set in a device having an infinite number of multiplying electrodes.
  • An electron multiplier comprising a primary cathode, a collector electrode, and a plurality of secondary cathodes between said primary cathode and said collector electrode and mounted in staggered relation in two rows, said secondary cathodes having opposed curved concave emissive surfaces the generatrices of which are parallel to a medial plane passing between said rows, and the end of each secondary cathode toward said collector electrode being spaced from the longitudinal axis of the opposite row of secondary cathodes a distance greater than the spacing between the end thereof toward said primary cathode and said axis of the opposite row of secondary cathodes.
  • An electron multiplier comprising a primary cathode, a collector electrode and a plurality of secondary cathodes mounted in staggered relation on opposite sides of the median line which spans the space between said primary cathode and said collector electrode, each of said secondary cathodes having an intermediate emissive portion and opposite emissive end-portions, one of the emissive end-portions being inclined toward said cathode and extending to said median line, and the other of said emissive end-portions being inclined toward said collector electrode and terminating short of said median line.

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  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Electron Tubes For Measurement (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
US171916A 1937-11-30 1937-11-30 Electron multiplier Expired - Lifetime US2231682A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
BE430852D BE430852A (xx) 1937-11-30
US177286A US2231691A (en) 1937-11-30 1937-11-30 Electron multiplier
US171916A US2231682A (en) 1937-11-30 1937-11-30 Electron multiplier
NL90376A NL57028C (xx) 1937-11-30 1938-10-26
FR845191D FR845191A (fr) 1937-11-30 1938-10-26 Perfectionnements aux multiplicateurs d'électrons
GB31156/38A GB520117A (en) 1937-11-30 1938-10-27 Improvements in or relating to electron multipliers
CH206023D CH206023A (de) 1937-11-30 1938-10-28 Elektronenvervielfacher.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US177286A US2231691A (en) 1937-11-30 1937-11-30 Electron multiplier
US171916A US2231682A (en) 1937-11-30 1937-11-30 Electron multiplier

Publications (1)

Publication Number Publication Date
US2231682A true US2231682A (en) 1941-02-11

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Application Number Title Priority Date Filing Date
US171916A Expired - Lifetime US2231682A (en) 1937-11-30 1937-11-30 Electron multiplier
US177286A Expired - Lifetime US2231691A (en) 1937-11-30 1937-11-30 Electron multiplier

Family Applications After (1)

Application Number Title Priority Date Filing Date
US177286A Expired - Lifetime US2231691A (en) 1937-11-30 1937-11-30 Electron multiplier

Country Status (6)

Country Link
US (2) US2231682A (xx)
BE (1) BE430852A (xx)
CH (1) CH206023A (xx)
FR (1) FR845191A (xx)
GB (1) GB520117A (xx)
NL (1) NL57028C (xx)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2664515A (en) * 1951-06-22 1953-12-29 Lincoln G Smith Magnetic electron multiplier
DE1022703B (de) * 1952-10-23 1958-01-16 Fernseh Gmbh Elektrostatischer Sekundaerelektronenvervielfacher
US4182968A (en) * 1976-04-23 1980-01-08 Rca Corporation Electron multiplier with ion bombardment shields

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL96507C (xx) * 1953-06-29
US2983845A (en) * 1959-05-07 1961-05-09 Bendix Corp Electron multiplier spurious noise baffle
US4142123A (en) * 1977-02-10 1979-02-27 Rca Corporation Image display device with optical feedback to cathode

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2664515A (en) * 1951-06-22 1953-12-29 Lincoln G Smith Magnetic electron multiplier
DE1022703B (de) * 1952-10-23 1958-01-16 Fernseh Gmbh Elektrostatischer Sekundaerelektronenvervielfacher
US4182968A (en) * 1976-04-23 1980-01-08 Rca Corporation Electron multiplier with ion bombardment shields

Also Published As

Publication number Publication date
FR845191A (fr) 1939-08-14
US2231691A (en) 1941-02-11
NL57028C (xx) 1946-03-15
GB520117A (en) 1940-04-15
BE430852A (xx)
CH206023A (de) 1939-07-15

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