US3265918A - Ion source having plasma control means - Google Patents

Ion source having plasma control means Download PDF

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Publication number
US3265918A
US3265918A US205168A US20516862A US3265918A US 3265918 A US3265918 A US 3265918A US 205168 A US205168 A US 205168A US 20516862 A US20516862 A US 20516862A US 3265918 A US3265918 A US 3265918A
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United States
Prior art keywords
aperture
plasma
anode
ion
ion source
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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
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US205168A
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English (en)
Inventor
Andrew B Wittkower
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High Voltage Engineering Corp
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High Voltage Engineering Corp
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Filing date
Publication date
Priority to NL285354D priority Critical patent/NL285354A/xx
Application filed by High Voltage Engineering Corp filed Critical High Voltage Engineering Corp
Priority to US205168A priority patent/US3265918A/en
Priority to DEH47471A priority patent/DE1233955B/de
Priority to GB44959/62A priority patent/GB971770A/en
Priority to FR916985A priority patent/FR1341088A/fr
Priority to CH1421062A priority patent/CH403995A/fr
Application granted granted Critical
Publication of US3265918A publication Critical patent/US3265918A/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
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns
    • H01J27/08—Ion sources; Ion guns using arc discharge
    • H01J27/10—Duoplasmatrons ; Duopigatrons

Definitions

  • Ion sources of the type comprehended by my invention generate ions through the discharge of a thermionic filament in the presence of hydrogen or other suitable ionizing gas.
  • the conventional arrangement includes an ionization chamber and means for supplying thereto a sufficient quantity of gas to be ionized.
  • a probe or intermediate electrode, having the filament disposed therein, is positioned in close proximity to an anode, said anode comprising the end wall and source aperture plate of the ionization chamber.
  • Axially aligned apertures in the probe [and anode together with appropriate potentials impressed thereon, provide arc discharge between filament and anode, ionization of gas residing therebetween, and emission of the ions thus formed through said anode aperture.
  • An extractor electrode having a relatively high potential with respect to the anode pulls ions in quantity through the anode aperture Iinto an evacuated ion source housing and directs such ions to a focussing elect-rode.
  • the focussing electrode in turn forms the ions into a beam which is made to focus at its point of application.
  • duoplasmatron ion .source can deliver an ion beam of this order of magnitude and greater, such a beam cannot be maintained in the ion source accelerator-extractor section, even at the highest gradient normally available for well-polished electrodes in vacuum, because of the space charge forces.
  • the effectiveness of an electrostatic lens is limited by a loss in beam quality due to spherical aberration which depends in part upon Ia function w3 where w is the angle of divergence of the beam as it enters the lens.
  • the focussing quality can, however, be materially increased for any ion beam of given parameters, if the diameter and divergence of such beam is a minimum when introduced to the focussing lens. This is accomplished by more effectively controlling the ions emanating from the source aperture, which control, in addition to achieving increased focussing range, results in m-ore efficient beam generation, fewer ions lost to the extractor electrode, and less gas flow into the ion source vacuu-m system.
  • FIGURE l is a graphical representation of the spacecharge expansion of ion beams emanating from various source apertures
  • FIGURE 2 il-lustrates a sectional view of an ion source embodying the principles of my invention
  • FIGURE 3 is an enlarged view of the source aperture electrode of FIGURE 2.
  • FIGURE 4 illustrates a sectional view of an alternate embodiment of my invention.
  • the ion beam divergence is controlled dominantly by space-charge forces. If the current, voltage, and mass composition are kept constant, there is a particular value of the initial beam radius ro for which the beam radius r at a particular distance z is a minimum.
  • the characteristics of three suc-h beams are illustrated by curves 31, 32;, 33 of FIGURE l.
  • V the beam energy in kiloelectron volts
  • l the beam current in milliamperes; and the integral etidt may be taken from tables in the publication Table of Functions by Eugene Janke and Fritz Emde.
  • the novel structure of my invention may be scaled to provide directed ion beams ranging from one milli-ampere to an ampere and higher.
  • FIGURE 2 there is illustrated an ion source of -the type comprehended by my invention.
  • hydrogen gas is injected into ionization chamber 36 by means of gas input conduit 6.
  • Probe 9 (also referred to as an intermediate or Swiss electrode) is centrally positioned in ionization chamber 36 and has disposed therein filament 8.
  • Filament supply 5 maintains the filament at about 200 volts with respect to anode 11.
  • Probe 9 is maintained at about -100 volts with respect to anode 11.
  • Magnet coil 7 shapes the discharge arc between filament 8 and anode 11, and concentrates the ions, formed by such discharge in the presence of hydrogen, in the anode aperture region.
  • Plasma control electrode 12 is positioned in close proximity to anode 11 and has its aperture in axial alignment with the anode and probe apertures.
  • An evacuated space i9 is provided between anode Il and plasma control electrode 12, a vacuum being maintained therein by means of opening i3 and vacuum pumping system 17.
  • Anode 11 and plasma control electrode 12 are maintained at 0 volt and in combination comprise the novel structure whereby several of the objectives of my invention are accomplished. Such structure will be hereinafter described in greater detail with reference to FIGURE 3.
  • Ions produced in ionization chamber 36 are drawn therefrom by extractor electrode 15, said electrode being maintained at a negative potential in the l0 kv. to 50 kv. range with respect to anode 11 and aligned to direct ions extracted therefrom to focussing electrode 16.
  • Said electrodes are disposed Within ion beam forming chamber 4 and are electrically isolated by insulators 10, f3, and 14.
  • FIGURE 3 With respect to the anode-plasma control electrode arrangement, an enlarged sectional View thereof is illustrated in FIGURE 3.
  • the relative dimensions are characteristic of an operable ion source in the ten milliampere beam class that has proved to successfully effect the objects and concepts of my invention.
  • aperture 25 of probe 9 has a diameter d2 of .09 inch.
  • Aperture 26 of anode l1 has a diameter d1 of .O09 inch and is in axial alignment with aperture 25.
  • plasma control electrode l2 positioned a distance d3 of .1 inch from anode Il has therein aperture 27 with a diameter d4 of .093 inch.
  • FIGURE 4 illustrates an alternate embodiment of my invention that is particularly adaptable to the production of high density ion beams.
  • cylindrical member 35 provides a drift space d5 wherein the plasma may expand to a diameter d6.
  • the plasma boundary -in the present case may be established by a grid 37, -or the plasma may be allowed te form its own boundary curvature. While it has been found that for most applications the natural plasma :boundary curvature iseifective, the use of a grid is still desirable in that it provides a definite boundary upon which initial calculations may be based.
  • the accelerating lens formed by the plasma boundary and extraction electrode 38 brings the beam to a minimum diameter at some discrete distance beyond the source and this distance may be varied by altering the plasma boundary curvature, the accelerating field configuration, or the aperture size.
  • this distance may be varied by altering the plasma boundary curvature, the accelerating field configuration, or the aperture size.
  • An ion source comprising an ionization chamber, means for supplying thereto a quantity of gas to be ionized, means for ionizing said gas, an evacuated plasma forming chamber, an apertured anode member, said anode member comprising a common partition between said ionization chamber and said plasma forming chamber, said anode member having an aperture therein of a size commensurate to the ion beam current requirements .of said ion source, a plasma control electrode at the potential of said anode member, an extractor electrode at a high potential with respect to that of said anode member, said plasma control electrode being in operable relationship with and spaced apart from said anode member, said space therebetween Ibeing sufficient to form a region free ⁇ of the influence of the extractor electrode for a distance over which the diiiusion of the plasma permits expansion of the plasma to the size considered desirable for ion extraction therefrom, said plasma control electrode having an aperture therein, said aperture being large with respect to said anode aperture and axially
  • plasma control means comprising, in combination, an anode, said anode constituting a common partition between said ionization chamber and said plasma forming chamber and having an aperture therein adapted to communicate a controlled quantity of ions therebetween, and a plasma control electrode at the potential of said anode member, an extractor el'ectrode at a high potential with respect to that of said anode member, said plasma control member being in yoperable relationship with said anode, said plasma control electrode Ibeing spaced relative to said anode by an amount suicient to form a region free of the influence of the extractor electrode for a distance -over which the diffusion of the plasma permits expansion of the plasma to the size considered desirable for ion extraction therefrom, said plasma control electrode having an aperture adapted to provide optimum divergence characteristics of an ion beam passing therethrough.
  • An ion source comprising an ionization chamber, means for supplying thereto a quantity of gas to be ionized, means for ionizing said gas, an evacuated plasma forming chamber, an apertured anode member, an extractor electrode at a high potential with respect to that of said anode member, said anode member comprising a common partition between said ionization chamber and said evacuated plasma forming chamber, said anode member having an aperture therein of a size commensurate to the ion beam current requirements of said ion source, said ion source producing a concentration of ions at said aperture suiciently great so that there would be a tendency for space charge repulsion to produce a highly divergent beam upon extraction of positive ions at that point,
  • a cylindrical member contiguous to and coaxially aligned with the aperture in said anode member and protruding into said ion beam forming chamber, said cylindrical member being at the same electrical potential as that of said anode member and being of sufficient length to form a region free of influence of the iield effect of the extractor electrode until such time as said plasma has diffused to a sucient extent to reduce space charge effects in the ion lbeam to be extracted therefrom, said cylindrical member thus providing a drift space adapted to allow expansion of plasma passing therethrough and having a diameter adapted to provide optimum divergence of the ion beam emanating therefrom, and a focussing electrode.
  • An ion source as dened in claim 3 including a plasma Iboundary forming grid disposed across said cylindrical member.
  • plasma control means comprising an anode, an extractor electrode at a high potential with respect to that of said anode, said anode constituting a common partition between said ionization chamber and said plasma forming chamber and having an aperture therein adapted to communicate a controlled quantity of ions therebetween, said ion source producing a concentration of ions at said aperture sufficiently great so that there would be a tendency for space charge repulsion to produce a highly divergent beam upon extraction of positive ions at that point, and an annular member contiguous thereto disposed in concentric relationship lto said aperture, said annular member lbeing at the same electrical potential as that of said anode and being of suicient length to form a region free of influence of the ield effect of the extractor electrode until such time as said plasma has diffused to a sufficient extent to reduce space charge eiiects in the ion beam to be extracted therefrom, said annular member
  • Plasma control means as defined in claim 5 including a plasma boundary forming grid disposed across said annular member.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Electron Sources, Ion Sources (AREA)
US205168A 1961-12-11 1962-06-18 Ion source having plasma control means Expired - Lifetime US3265918A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
NL285354D NL285354A (enrdf_load_stackoverflow) 1961-12-11
US205168A US3265918A (en) 1961-12-11 1962-06-18 Ion source having plasma control means
DEH47471A DE1233955B (de) 1961-12-11 1962-11-22 Ionenquelle
GB44959/62A GB971770A (en) 1961-12-11 1962-11-28 Ion source
FR916985A FR1341088A (fr) 1961-12-11 1962-11-29 Générateur d'ions
CH1421062A CH403995A (fr) 1961-12-11 1962-12-04 Générateur d'ions

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US15820661A 1961-12-11 1961-12-11
US205168A US3265918A (en) 1961-12-11 1962-06-18 Ion source having plasma control means

Publications (1)

Publication Number Publication Date
US3265918A true US3265918A (en) 1966-08-09

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US (1) US3265918A (enrdf_load_stackoverflow)
CH (1) CH403995A (enrdf_load_stackoverflow)
DE (1) DE1233955B (enrdf_load_stackoverflow)
GB (1) GB971770A (enrdf_load_stackoverflow)
NL (1) NL285354A (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3458743A (en) * 1966-12-19 1969-07-29 Radiation Dynamics Positive ion source for use with a duoplasmatron
US3573523A (en) * 1967-09-07 1971-04-06 Leybold Heraeus Verwaltung Vacuum gauge arrangement provided with a flange connection
US3702416A (en) * 1969-04-04 1972-11-07 Lucien Bex Ion source having a uniform radial density
US3890535A (en) * 1971-10-13 1975-06-17 Anvar Ion sources
US3924134A (en) * 1974-11-29 1975-12-02 Ibm Double chamber ion source
US4020384A (en) * 1975-08-25 1977-04-26 The Raymond Lee Organization, Inc. Linear particle accelerator
US4103202A (en) * 1976-12-03 1978-07-25 Klykon, Inc. Ion projector head
US20100320395A1 (en) * 1999-12-13 2010-12-23 Semequip, Inc. External cathode ion source

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2969480A (en) * 1958-05-03 1961-01-24 Commissariat Energie Atomique Ion sources
US2975277A (en) * 1955-05-10 1961-03-14 Vakutronik Veb Ion source

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1001429B (de) * 1955-06-27 1957-01-24 Siemens Ag Ionenquelle
DE1059581B (de) * 1956-03-28 1959-06-18 Siemens Ag Plasmaquelle fuer geladene Teilchen
DE1014671B (de) * 1956-04-24 1957-08-29 Siemens Ag Einrichtung zur Erzeugung mehrfach geladener Ionen in einer Bogenentladungsquelle
FR1262136A (fr) * 1960-06-20 1961-05-26 Vakutronik Veb Source d'ions et d'électrons, notamment pour générateurs de van de graaff

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975277A (en) * 1955-05-10 1961-03-14 Vakutronik Veb Ion source
US2969480A (en) * 1958-05-03 1961-01-24 Commissariat Energie Atomique Ion sources

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3458743A (en) * 1966-12-19 1969-07-29 Radiation Dynamics Positive ion source for use with a duoplasmatron
US3573523A (en) * 1967-09-07 1971-04-06 Leybold Heraeus Verwaltung Vacuum gauge arrangement provided with a flange connection
US3702416A (en) * 1969-04-04 1972-11-07 Lucien Bex Ion source having a uniform radial density
US3890535A (en) * 1971-10-13 1975-06-17 Anvar Ion sources
US3924134A (en) * 1974-11-29 1975-12-02 Ibm Double chamber ion source
US4020384A (en) * 1975-08-25 1977-04-26 The Raymond Lee Organization, Inc. Linear particle accelerator
US4103202A (en) * 1976-12-03 1978-07-25 Klykon, Inc. Ion projector head
US20100320395A1 (en) * 1999-12-13 2010-12-23 Semequip, Inc. External cathode ion source
US8502161B2 (en) * 1999-12-13 2013-08-06 Semequip, Inc. External cathode ion source

Also Published As

Publication number Publication date
CH403995A (fr) 1965-12-15
NL285354A (enrdf_load_stackoverflow)
GB971770A (en) 1964-10-07
DE1233955B (de) 1967-02-09

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