US3833829A - Ion source - Google Patents

Ion source Download PDF

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Publication number
US3833829A
US3833829A US00315096A US31509672A US3833829A US 3833829 A US3833829 A US 3833829A US 00315096 A US00315096 A US 00315096A US 31509672 A US31509672 A US 31509672A US 3833829 A US3833829 A US 3833829A
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US
United States
Prior art keywords
ion source
cathode
ion
anode
magnetic field
Prior art date
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Expired - Lifetime
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US00315096A
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English (en)
Inventor
O Reifenschweiler
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US Philips Corp
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US Philips Corp
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Filing date
Publication date
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Publication of US3833829A publication Critical patent/US3833829A/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H3/00—Production or acceleration of neutral particle beams, e.g. molecular or atomic beams
    • H05H3/06—Generating neutron beams
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns
    • H01J27/04—Ion sources; Ion guns using reflex discharge, e.g. Penning ion sources

Definitions

  • An ion source having an anode between two cathodes and means for producing an axial magnetic field.
  • the invention relates to an ion source comprising a first cathode, a second cathode having an ion exit aperture, an anode between the two cathodes, and means for producing an axial magnetic field.
  • Such an ion source is known from the US. Pat. No. 3,408,526 and has the advantage that it can operate at a comparatively low gas pressure. This is caused by the fact that the electrons which are formed in the gas discharge between the anode and the two cathodes can move only mainly in the direction of the lines of force of the magnetic field and thus cover a long track before they reach the anode. Also in the case of a comparatively low pressure, this long track results in a large ionization possibility per electron.
  • a beam of ions is extracted from the ion source by applying a potential difference between an accelerating electrode and the cathode with the ion exit aperture.
  • the accelerated ions then impinge generally upon a target the shape of which is determined by the nature of the device in which the ion source is used.
  • a part of the ions of the ion beam ionizes the gas which is present in the space in which the accelerating field prevails.
  • the resulting formed electrons and negative ions, if the ions supplied by the ion source are positive, and positive ions, if the ion source supplies negative ions, respectively, are accelerated in the reverse direction by the accelerating field.
  • the object of the invention to provide an ion source in which said drawbacks do not occur and for that purpose the invention is characterized in that the first cathode and the means for producing an axial magnetic field comprise an axial aperture and the ion source furthermore comprises a collector electrode on the side of the first cathode remote from the anode.
  • the collector electrode preferably comprises a funnel-like cavity as a result of which the evolved thermal energy is distributed over a large area.
  • the neutron generator shown is of the sealed type and comprises in an envelope 1 a gas mixture consisting of 50 percent deuterium and 50 percent tritium at a pressure of approximately X mm Hg.
  • the gas mixture is supplied and its pressure maintained at the correct value by a pressure control 2.
  • the pressure control comprises a large quantity of the gas mixture.
  • the mixture of deuterium and tritium is ionized in the ion source 3 and a beam of positive deuterium ions and tritium ions is extracted from the ion source by the accelerating electrode 4.
  • the ion source is at a positive voltage of 250 kV relative to the accelerating electrode 4.
  • the formed ion beam passes the screen electrode 5 and impinges upon the target 6.
  • the target 6 consists of a base plate 7 of a material having a small absorption coefficient and diffusion coefficient for deuterium and tritium (for example, copper) and a reaction layer 8 of a material having a large absorption coefficient for deuterium and tritium.
  • the reaction layer 8 consists of a 5 ,um thick layer of titanium.
  • the target 6 has been provided in the neutron generator without having been saturated with deuterium and tritium and in the first hours of life of the generator it absorbs deuterium and tritium from the ion beam impinging upon the target 6.
  • the absorbed deuterium and tritium cannot diffuse away to any considerable extent to places in the target 6 which are present at a deeper location than the thickness of the reaction layer 8, because the base plate 7 has a small absorption coefficient and diffusion coefficient for deuterium and tritium.
  • the result is that the reaction layer 8 is ever more strongly saturated with deuterium and tritium as a result of which the neutron output begins.
  • the neutron output occurs in particular from the reaction between deuterium and tritium.
  • the collision with an energy of 250 keV between a deuterium nucleus and a tritium nucleus supplies a neutron having an energy of 14 MeV and an alpha particle having an energy of 3.6 MeV. It is to be noted that neutrons are formed to a small extent from the reaction between two deuterium nuclei. These neutrons have a much smaller energy.
  • the neutrons having an energy of 14 MeV constitute the effective output of approximately 10 neutrons per second of the generator. After a few hours in operation said neutron output is reached when the saturation of the reaction layer 8 with deuterium and tritium has reached an equilibrium condition.
  • the accelerating electrode 4 has a negative potential of a few hundred volts relative to the screen electrode 5 and the target 6 to prevent secondary electrons which are formed on the target 6 from being accelerated towards the ion source 3.
  • the neutron generator furthermore comprises an ionization manometer 9 for check ing the gas pressure.
  • the ion source 3 comprises an anode 10, a first cathode 11 and a second cathode 12.
  • the cathodes l1 and 12 have the same potential.
  • the anode 10 has a positive potential of 3 kV relative to the cathodes 11 and 12.
  • the ion source 3 furthermore comprises a permanent magnet 13 consisting of six permanent magnetic rings which are magnetized so that an axial magnetic field is formed having a main orientation parallel to the arrow 14.
  • a permanent magnetic ring 15 is magnetized so that said field is intensified in the proximity of the second cathode 12.
  • the magnetic circuit of which the permanent magnets 13 and 15 form part is closed by the ferromagnetic sleeve 16 bypassing the anode 10.
  • the anode voltage is supplied via the connection 17.
  • the high voltage which brings the cathodes 11 and 12 at a potential of 250 kV relative to the accelerating electrode 4 is supplied via the connection 18.
  • Negative ions and electrons which are formed by ionization with the ion beam in the region 19 are accelerated in the direction of the ion source 3.
  • Negative ions and electrons which are formed by ionization with the ion beam in the region 19 are accelerated in the direction of the ion source 3.
  • they When said negative particles have reached the ion source, they have a larger energy according as they have been formed closer in the proximity of the accelerating electrode 4 and can thus have an energy of 250 keV.
  • These particles pass the ion exit aperture in the second cathode 12 in the reverse direction but in an ion source according to the invention they do not impinge upon the first cathode 11 as a result of which same would be heated such that the permanent magnet 13 would be damaged and cathode material be sputtered throughout the ion source.
  • the first cathode 11 and the permanent magnet 13 comprise an axial aperture 21 through which the particles in question pass after which they impinge upon a collector electrode 22.
  • the collector electrode 22 is at the same potential as the cathodes 11 and 12 and is mounted in such manner that the evolved heat cannot produce any damage.
  • the collector electrode 22 comprises a funnel-like cavity 23 which serves to distribute the evolved thermal energy over an area which is as large as possible. It is to be noted that only negative particles of large energy can reach the collector electrode 22.
  • Negative ions and electrons which are formed during the ionization process in the ion source itself cannot reach a potential which is lower than the cathode potential and thus only a small number of them can reach the aperture 21 which forms an equipotential space at cathode potential.
  • the ion beam which is extracted from the ion source has a current strength of approximately 15 mA.
  • the gas discharge in the ion source 3 results in an anode current of approximately 50 mA.
  • the accelerated ion beam of an energy of 250 keV results in a neutron output of approximately 10 neutrons per second.
  • the neutron generator may be used for scientific purposes such as activation analysis and, as a result of its high neutron output, it is particularly suitable for medical applications such as cancer therapy, total body activation analysis and measurement of the blood circulation.
  • An ion source comprising a first cathode, a second cathode having an ion exit aperture, an anode between the two cathodes, and means forproducing an axial magnetic field, characterized in that the first cathode and the means for producing an axial magnetic field comprise an axial aperture and that the ion source furthermore comprises a collector electrode on the side of the first cathode remote from the anode.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Plasma & Fusion (AREA)
  • Particle Accelerators (AREA)
  • Electron Sources, Ion Sources (AREA)
US00315096A 1972-01-03 1972-12-14 Ion source Expired - Lifetime US3833829A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL7200001A NL7200001A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1972-01-03 1972-01-03

Publications (1)

Publication Number Publication Date
US3833829A true US3833829A (en) 1974-09-03

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ID=19815075

Family Applications (1)

Application Number Title Priority Date Filing Date
US00315096A Expired - Lifetime US3833829A (en) 1972-01-03 1972-12-14 Ion source

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Country Link
US (1) US3833829A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
JP (1) JPS524719B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
CA (1) CA984979A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DE (1) DE2261720C3 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
FR (1) FR2167619B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
GB (1) GB1351582A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
NL (1) NL7200001A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0015391A1 (de) * 1979-03-03 1980-09-17 Vacuumschmelze GmbH Glimmentladungslampe zur qualitativen und quantitativen Spektralanalyse
US4529571A (en) * 1982-10-27 1985-07-16 The United States Of America As Represented By The United States Department Of Energy Single-ring magnetic cusp low gas pressure ion source
US5053184A (en) * 1988-04-26 1991-10-01 U.S. Philips Corporation Device for improving the service life and the reliability of a sealed high-flux neutron tube

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0004962A1 (de) * 1978-04-20 1979-10-31 Vacuumschmelze GmbH Glimmentladungslampe zur qualitativen und quantitativen Spektralanalyse
RU2372755C1 (ru) * 2008-02-07 2009-11-10 Федеральное государственное унитарное предприятие "Всероссийский научно-исследовательский институт автоматики им. Н.Л. Духова" Газонаполненная нейтронная трубка с источником пеннинга
CN115541635B (zh) * 2022-11-25 2023-03-10 中国工程物理研究院材料研究所 一种d-t中子成像方法及系统

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0015391A1 (de) * 1979-03-03 1980-09-17 Vacuumschmelze GmbH Glimmentladungslampe zur qualitativen und quantitativen Spektralanalyse
US4529571A (en) * 1982-10-27 1985-07-16 The United States Of America As Represented By The United States Department Of Energy Single-ring magnetic cusp low gas pressure ion source
US5053184A (en) * 1988-04-26 1991-10-01 U.S. Philips Corporation Device for improving the service life and the reliability of a sealed high-flux neutron tube

Also Published As

Publication number Publication date
GB1351582A (en) 1974-05-01
NL7200001A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1973-07-05
CA984979A (en) 1976-03-02
JPS4873700A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1973-10-04
FR2167619B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1977-09-02
JPS524719B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1977-02-05
DE2261720C3 (de) 1979-02-22
DE2261720A1 (de) 1973-07-19
DE2261720B2 (de) 1978-06-08
FR2167619A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1973-08-24

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