US3342404A - Annular electrodes in differential pumping tubes for electrostatic accelerators - Google Patents

Annular electrodes in differential pumping tubes for electrostatic accelerators Download PDF

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Publication number
US3342404A
US3342404A US507426A US50742665A US3342404A US 3342404 A US3342404 A US 3342404A US 507426 A US507426 A US 507426A US 50742665 A US50742665 A US 50742665A US 3342404 A US3342404 A US 3342404A
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United States
Prior art keywords
tube
electrode
electrodes
axis
bars
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Expired - Lifetime
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US507426A
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English (en)
Inventor
Howe Frederick Albert
Bell Ronald Inch
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UK Atomic Energy Authority
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UK Atomic Energy Authority
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J41/00—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas; Discharge tubes for evacuation by diffusion of ions
    • H01J41/12—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps
    • H01J41/18—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps with ionisation by means of cold cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J5/00—Details relating to vessels or to leading-in conductors common to two or more basic types of discharge tubes or lamps
    • H01J5/02—Vessels; Containers; Shields associated therewith; Vacuum locks
    • H01J5/06—Vessels or containers specially adapted for operation at high tension, e.g. by improved potential distribution over surface of vessel

Definitions

  • a differential pumping tube for evacuating the highvoltage portion of an electrostatic accelerator in parallel with the accelerating tube is of the type comprising a plurality of annular electrodes spaced apart by annular insulators, and is improved by including in each electrode a substantially diametrical bar which intersects the axis of the tube, the two radial halves of the bar being deflected from a plane normal to the tube axis toward one end of the tube to produce an electric field between adjacent electrodes having a component directed toward the tube axis to cause deflection of unwanted electrons into the electrodes.
  • each electrode may also be deflected from the plane toward the one end of the tube to enhance the electric field, and preferably each successive electrode has its bar circumferentially displaced through a small angle relative to the bar of the preceding electrode to provide optical baffling along the tube.
  • This invention relates to dilferential pumping tubes for electrostatic accelerators.
  • a well known phenomenon in electrostatic accelerators is electron loading, in which electrons are accelerated back towards the positive end of the tube.
  • the accelerated electrons which can originate in various ways, e.g. by field emission from the electrodes, generate X-rays when they strike parts of the accelerator structure, which in turn ionise the high-pressure gas surrounding the structure and so reduce the insulation.
  • the electrons themselves constitute an additional load on the generator, tending to reduce its output voltage.
  • accelerating tube Various forms of accelerating tube have been proposed to suppress the electron loading effect. These are usually designed to deflect the electrons into the tube structure before they have acquired sufiicient energy to have a serious effect. It is an object of the present invention to provide a differential pumping tube which combines a high degree of electron suppression with low impedance to gas fiow.
  • a difl erential pumping tube comprises a plurality of annular electrodes spaced apart by annular insulators, each electrode including a substantially diametral bar whereof the two radial halves are deflected from a plane normal to the tube axis towards one end of the tube to produce an electric field between adjacent electrodes having a component directed towards the tube axis.
  • each electrode is also deflected from said plane to enhance said field as aforesaid.
  • each bar is circumferentially displaced by a small angle relative to the bar of the preceding electrode to provide optical baflling along the tube.
  • the bars may be deflected to V-shape or arcuate form.
  • FIGURE 1 is a cross-sectional elevation of part of a pumping tube embodying the present invention.
  • FIGURE 2 is an axial view looking through the tube of FIGURE 1.
  • FIGURE 3 shows a modification of the tube of FIG- URE 1.
  • a pumping tube comprises a plurality of aluminum electrodes 1 (of which only two are shown complete) separated by annular glass insulators 2 and having an inner periphery 3. Extending diametrically between two points on the inner periphery of each electrode is a bar, the two radial halves 4a and 4b of which are deflected from the plane of the electrode (which is normal to the tube axis) to meet in a V on the tube axis. The effect is to produce an electric field between adjacent electrodes, indicated by the arrows, which has a component directed towards the tube axis. This component causes any electrons within the tube to impinge on the bars instead of travelling along the tube parallel to the axis.
  • the radial component of electric field might be insufficient to prevent some movement of electrons parallel to the axis.
  • the entire inner periphery is itself deflected, at approximately the same angle as the two halves of the bar.
  • the bars are made sufficiently narrow to ofier little impedance to the flow of gas along the tube.
  • successive electrodes are mounted with their bars circumferentially displaced through a small angle relative to the preceding bar to produce an optical bafiling effect looking along the tube axis.
  • the eflect is illustrated in FIGURE 2, where the angular displacement between successive bars is 15'. It will be seen that with the dimensions shown, no electron travelling parallel to the tube axis can traverse more than eleven electrodes without impinging on a bar.
  • FIGURES 1 and 2 illustrate the described embodiment approximately to scale, the diameter of the edge of the inner periphery being 5% inches.
  • the bars are inch wide at the periphery, tapering to /2 inch at the axis.
  • the electrodes are spaced 1.1 inches apart by the insulators.
  • the diametral bars 4 have the same dimensions as in FIG- URES 1 and 2 and are circumferentially displaced by the same amount. However instead of being deflected to a V-shape, the bars 4' are arcuate in form, the centre of the are (where it intersects the tube axis) being displaced about 1% inches from the plane of the electrode.
  • An example of this embodiment, comprising 136 such electrodes spaced 1.1 inches apart, has been used at voltages up to 5.5 mv. with no measurable electron loading. The pumping impedance of this tube with air was approximately 28 litres/sec.
  • each electrode includes a substantially diametrical bar which intersects the axis of the tube, the two radial halves of said bar being deflected from a plane normal to the tube axis towards one end of the tube to produce an electric field between adjacent electrodes having a component directed towards the tube axis to cause deflection of unwanted electrons into said electrodes.

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  • Particle Accelerators (AREA)
US507426A 1964-11-19 1965-11-12 Annular electrodes in differential pumping tubes for electrostatic accelerators Expired - Lifetime US3342404A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB47158/64A GB1087725A (en) 1964-11-19 1964-11-19 Improvements in or relating to differential pumping-tubes for electrostatic particle accelerators

Publications (1)

Publication Number Publication Date
US3342404A true US3342404A (en) 1967-09-19

Family

ID=10443957

Family Applications (1)

Application Number Title Priority Date Filing Date
US507426A Expired - Lifetime US3342404A (en) 1964-11-19 1965-11-12 Annular electrodes in differential pumping tubes for electrostatic accelerators

Country Status (5)

Country Link
US (1) US3342404A (enrdf_load_stackoverflow)
DE (1) DE1299777B (enrdf_load_stackoverflow)
FR (1) FR1455570A (enrdf_load_stackoverflow)
GB (1) GB1087725A (enrdf_load_stackoverflow)
NL (1) NL6515010A (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3816771A (en) * 1973-02-09 1974-06-11 Atomic Energy Commission Plasma energy to electrical energy converter
CN104582230A (zh) * 2014-12-11 2015-04-29 中国原子能科学研究院 一种静电加速器的加速电极

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2570158A (en) * 1950-12-02 1951-10-02 Gen Electric Method and apparatus for separating charged particles of different mass-to-charge ratios
US2917630A (en) * 1955-03-01 1959-12-15 Walbank Thomas Apparatus for treating inert gas
US3174678A (en) * 1960-12-01 1965-03-23 Thomson Houston Comp Francaise Vacuum pumps
US3175373A (en) * 1963-12-13 1965-03-30 Aero Vac Corp Combination trap and baffle for high vacuum systems

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB967963A (en) * 1961-08-11 1964-08-26 Nat Inst For Res In Nuclear Sc Improvements in or relating to particle accelerating tubes

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2570158A (en) * 1950-12-02 1951-10-02 Gen Electric Method and apparatus for separating charged particles of different mass-to-charge ratios
US2917630A (en) * 1955-03-01 1959-12-15 Walbank Thomas Apparatus for treating inert gas
US3174678A (en) * 1960-12-01 1965-03-23 Thomson Houston Comp Francaise Vacuum pumps
US3175373A (en) * 1963-12-13 1965-03-30 Aero Vac Corp Combination trap and baffle for high vacuum systems

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3816771A (en) * 1973-02-09 1974-06-11 Atomic Energy Commission Plasma energy to electrical energy converter
CN104582230A (zh) * 2014-12-11 2015-04-29 中国原子能科学研究院 一种静电加速器的加速电极

Also Published As

Publication number Publication date
NL6515010A (enrdf_load_stackoverflow) 1966-05-20
GB1087725A (en) 1967-10-18
DE1299777B (de) 1969-07-24
FR1455570A (fr) 1966-10-14

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