EP1220289A2 - Plasmamassenfilter - Google Patents

Plasmamassenfilter Download PDF

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Publication number
EP1220289A2
EP1220289A2 EP01202936A EP01202936A EP1220289A2 EP 1220289 A2 EP1220289 A2 EP 1220289A2 EP 01202936 A EP01202936 A EP 01202936A EP 01202936 A EP01202936 A EP 01202936A EP 1220289 A2 EP1220289 A2 EP 1220289A2
Authority
EP
European Patent Office
Prior art keywords
particles
chamber
central axis
recited
selector
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.)
Withdrawn
Application number
EP01202936A
Other languages
English (en)
French (fr)
Other versions
EP1220289A3 (de
Inventor
Tihiro Ohkawa
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.)
Archimedes Technology Group Inc
Original Assignee
Archimedes Technology Group Inc
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 Archimedes Technology Group Inc filed Critical Archimedes Technology Group Inc
Publication of EP1220289A2 publication Critical patent/EP1220289A2/de
Publication of EP1220289A3 publication Critical patent/EP1220289A3/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/28—Static spectrometers
    • H01J49/284—Static spectrometers using electrostatic and magnetic sectors with simple focusing, e.g. with parallel fields such as Aston spectrometer
    • H01J49/286—Static spectrometers using electrostatic and magnetic sectors with simple focusing, e.g. with parallel fields such as Aston spectrometer with energy analysis, e.g. Castaing filter
    • H01J49/288—Static spectrometers using electrostatic and magnetic sectors with simple focusing, e.g. with parallel fields such as Aston spectrometer with energy analysis, e.g. Castaing filter using crossed electric and magnetic fields perpendicular to the beam, e.g. Wien filter

Definitions

  • the present invention pertains generally to particle filters. More particularly, the present invention pertains to devices and methods for removing selected particles from a partially ionized multi-species plasma. The present invention is particularly, but not exclusively, useful as a device and method for establishing resonance with selected particles in a plasma, to control the movement of these selected particles in a manner that will cause them to be removed or separated from other non-selected particles in the plasma.
  • a neutral gas such as Argon e.g. a neutral gas such as Argon
  • the charged particles will also have different mass-charge ratios.
  • cyclotron resonance can be achieved by coupling electromagnetic power into a system of charged particles that are undergoing orbital movement in a uniform magnetic field.
  • these concepts still pertain. Additionally, however, in a partially ionized multi-species plasma the effect of collisions between ions and neutrals is also of importance.
  • selected particles in a partially ionized plasma can be excited at their cyclotron frequency and thereby be forced to drift or spiral inwardly toward a central axis.
  • non-selected particles in the plasma will be allowed to continue to drift radially outward from the central axis.
  • a plasma mass selector for processing a partially ionized multi-species plasma includes a generally cylindrical chamber that has a wall and defines a central axis.
  • An injector is provided for introducing the partially ionized plasma into the chamber.
  • the partially ionized multi-species plasma will have at least three identifiable constituents. These are: 1) neutrals, such as are present in an inert gas (e.g. Argon); 2) particles that have a relatively low mass-charge ratio (M 1 ) and a cyclotron frequency ( ⁇ 1 ); and 3) particles that have a relatively high mass-charge ratio (M 2 ) and a cyclotron frequency ( ⁇ 2 ).
  • the selector also includes a plurality of magnetic coils that are mounted on the chamber to establish a substantially uniform magnetic field inside the chamber. More specifically, the magnetic field is oriented so as to be substantially parallel to the central axis.
  • a quadrupole electrode is positioned to create a non-uniform cyclotron electric field (NCEF) inside the chamber.
  • NCEF non-uniform cyclotron electric field
  • the NCEF electric field is oriented substantially perpendicular to the central axis in order to establish crossed electric and magnetic fields inside the chamber.
  • the quadrupole electrode comprises a plurality of concentric coplanar rings that are divided into quadrant segments. With this configuration, the quadrupole electrode is selectively operable at either the cyclotron frequency ⁇ 1 or ⁇ 2 to respectively resonate with the particles M 1 or M 2 .
  • the effect is to restrain the particles M 1 in orbits around the central axis for transit through the chamber, while allowing the particles M 2 to drift radially outward from the central axis for collision with the wall.
  • the quadrupole electrode is operated at ⁇ 2 the effect is to restrain the particles M 2 in orbits around the central axis for transit through the chamber, while allowing the particles M 1 to drift radially outward from the central axis for collision with the wall.
  • a plasma mass selector in accordance with the present invention is shown and is generally designated 10.
  • the selector 10 includes a chamber 12 surrounded by a wall 14 that is located at a distance from a central axis 16.
  • the chamber 12 is cylindrically shaped, and the central axis 16 is substantially the longitudinal axis of the cylinder.
  • the selector 10 includes an injector 18 for introducing a partially ionized multi-species plasma into the chamber 12.
  • this partially ionized plasma contains neutrals, such as are present in an inert gas (e.g. Argon, Ar).
  • the partially ionized plasma will contain particles of relatively low mass-charge ratio (M 1 ) and particles of relatively high mass-charge ratio (M 2 ). These particles M 1 and M 2 will have respective cyclotron frequencies ⁇ 1 and ⁇ 2 . It will be appreciated that the partially ionized plasma that is to be processed by the selector 10 in accordance with the present invention may also contain additional charged particles having mass-charge ratios that are different from M 1 and M 2 .
  • the selector 10 includes a plurality of magnetic coils 20, of which the magnetic coils 20a and 20b are only exemplary.
  • the magnetic coils 20a and 20b are mounted externally on the chamber 12 and can be activated in a manner well known in the pertinent art to generate a generally uniform magnetic field, B, inside the chamber 12.
  • this magnetic field B will be oriented substantially parallel to the central axis 16 inside the chamber 12.
  • Fig. 1 also shows that the selector 10 includes a quadrupole electrode which is made up of a plurality of coplanar electrode rings 22. As shown, the electrode rings 22 collectively lie in a plane that is oriented substantially perpendicular to the central axis 16.
  • the electrode rings 22a and 22b shown in Fig. 1 are only exemplary. In the orientation disclosed, the electrode rings 22 generate a radially oriented electric field, E, that is generally perpendicular to the central axis 16. Accordingly, there are crossed electric and magnetic fields (E x B) inside the chamber 12.
  • the configuration for the electrode rings 22 is such that quadrant electrode segments 24 are created. As indicated in Fig. 1, these quadrant electrode segments 24 are identified as 24a, 24b, 24c and 24d.
  • the segments 24a-d can be selectively activated such that electric fields are generated between adjacent segments by applying voltage to diametrically opposed pairs.
  • the quadrant segments 24a and 24c can be activated, while quadrant segments 24b and 24d are idle This results in a voltage between 24a and respectively 24b, 24c and 24d.
  • This can then be changed so that the quadrant segments 24b and 24d are activated to generate electric fields while the quadrants 24a and 24c are idle. Further, this change over can be accomplished at a predetermined selectable frequency, ⁇ .
  • the drift reversal condition for the resonant ions can be written using the above condition ⁇ 2 > [v s / L][8/3] 1/2
  • Figs. 2A and 2B specifically illustrate the trajectory for an orbit 26 that will be followed around the axis 16 by a particle of mass-charge ratio M 2 when the particle M 2 begins at a start point 28.
  • the orbit 26 will result when the particle M 2 is not resonantly accelerated as it traverses through the chamber 12.
  • a drag force, D will be imposed on the particle M 2 .
  • the drag force D will cause the particle M 2 to spiral outwardly from the central axis 16 and follow the orbit 26, as shown in Figs. 2A and 2B.
  • Figs. 3A and 3B specifically illustrate an orbit 30 that will be followed by a particle of mass-charge ration M 1 when the particle M 1 begins at a start point 32 and is resonantly accelerated as it traverses through the chamber 12.
  • a particle e.g. the particle M 1
  • a force P on the particle that will act opposite to the drag force D.
  • the generation of this propelling force, P is accomplished by selectively activating the electrode quadrant segments 24a-d.
  • the force P is generated on a particle M 1 by operating the electrode quadrant segments 24 at the cyclotron frequency of the particle M 1 (i.e. ⁇ 1 ).
  • a resonant condition is established with the particle M 1 that does not affect the particle M 2 .
  • the electrode quadrant segments 24a-d are operated at the cyclotron frequency of the particle M 2 (i.e. ⁇ 2 ) the particles M 2 , instead of the particles M 1 , will be resonantly accelerated to follow trajectories having a configuration similar to the orbit 30.
  • any particle M that is resonantly accelerated at its cyclotron frequency will spiral inwardly toward the central axis 16 (i.e. orbit 30). Consequently, resonantly accelerated particles will be allowed to travel through the chamber 12.
  • the particles that are not resonantly accelerated, however, will spiral outwardly away from the central axis 16 (i.e. orbit 26) and will collide with the wall 14 before they complete a transit through the chamber 12.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Sources, Ion Sources (AREA)
  • Electron Tubes For Measurement (AREA)
EP01202936A 2000-08-08 2001-08-02 Plasmamassenfilter Withdrawn EP1220289A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US63466500A 2000-08-08 2000-08-08
US634665 2000-08-08

Publications (2)

Publication Number Publication Date
EP1220289A2 true EP1220289A2 (de) 2002-07-03
EP1220289A3 EP1220289A3 (de) 2003-05-14

Family

ID=24544729

Family Applications (1)

Application Number Title Priority Date Filing Date
EP01202936A Withdrawn EP1220289A3 (de) 2000-08-08 2001-08-02 Plasmamassenfilter

Country Status (2)

Country Link
EP (1) EP1220289A3 (de)
JP (1) JP2002150994A (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114501768B (zh) * 2022-01-30 2023-04-18 清华大学 加速器带电粒子束电流压缩装置及方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4093856A (en) * 1976-06-09 1978-06-06 Trw Inc. Method of and apparatus for the electrostatic excitation of ions
EP1001450A2 (de) * 1998-11-16 2000-05-17 Archimedes Technology Group, Inc. Plasma-Massenfilter

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4093856A (en) * 1976-06-09 1978-06-06 Trw Inc. Method of and apparatus for the electrostatic excitation of ions
EP1001450A2 (de) * 1998-11-16 2000-05-17 Archimedes Technology Group, Inc. Plasma-Massenfilter

Also Published As

Publication number Publication date
EP1220289A3 (de) 2003-05-14
JP2002150994A (ja) 2002-05-24

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