WO2004002201A1 - Generateur de faisceau de plasma - Google Patents

Generateur de faisceau de plasma Download PDF

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Publication number
WO2004002201A1
WO2004002201A1 PCT/AU2003/000763 AU0300763W WO2004002201A1 WO 2004002201 A1 WO2004002201 A1 WO 2004002201A1 AU 0300763 W AU0300763 W AU 0300763W WO 2004002201 A1 WO2004002201 A1 WO 2004002201A1
Authority
WO
WIPO (PCT)
Prior art keywords
plasma
plasma beam
producing
source volume
containment vessel
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.)
Ceased
Application number
PCT/AU2003/000763
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English (en)
Inventor
Roderick Boswell
Christine Charles
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.)
Australian National University
Original Assignee
Australian National University
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 Australian National University filed Critical Australian National University
Priority to AU2003232523A priority Critical patent/AU2003232523A1/en
Publication of WO2004002201A1 publication Critical patent/WO2004002201A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/54—Plasma accelerators
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
    • B64G1/00—Cosmonautic vehicles
    • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
    • B64G1/40—Arrangements or adaptations of propulsion systems
    • B64G1/411—Electric propulsion
    • B64G1/413—Ion or plasma engines

Definitions

  • the present invention relates to the generation of a plasma beam from a high density plasma source.
  • a plasma beam can be used to provide thrust for a spacecraft or for other applications for example, irradiation of a surface to change the properties of the surface.
  • a spacecraft thruster it is applicable to such other uses.
  • a subset of electrical propulsion devices is the plasma thruster in which a gas, commonly Xenon is injected into a chamber and ionised by electrons from a cathode, which may be heated, or by high frequency electric fields.
  • a gas commonly Xenon
  • cathode which may be heated, or by high frequency electric fields.
  • Gridded ion extraction is one of the most popular and best tested methods of accelerating ions from the plasma source into space.
  • An arrangement of typically three grids, normally constructed from three plates with many small concentric holes have voltages applied to them which accelerate the ions from the plasma producing a positively charged ion beam.
  • An electron source such as a hollow cathode plasma source is placed outside the plasma source/acceleration grid system to allow electrons to mix with the positively charged ion beam and neutralise it. This is necessary to prevent the spacecraft charging up negatively which would attract the ion beam back and cause damage.
  • a disadvantage of using grids to extract ions is erosion of the grids by ion induced physical sputtering and consequent growth of 'whiskers' which can short circuit the acceleration electrodes.
  • this invention provides a plasma beam generator comprising a containment vessel having a first end, a second end, and defining a plasma source volume, said second end being open for expulsion of plasma; a gas inlet adjacent said first end for supply of plasma producing gas; a plasma generator to generate a high density plasma in said source volume; and a magnetic field generator to generate an axial magnetic field directed from the source volume and expanding gradually through said second end; wherein an electric double layer is established between the source volume and said second end.
  • this invention provides a method of producing a plasma beam comprising the steps of supplying a plasma producing gas to a containment vessel having a first end, a second end open for expulsion of plasma, and defining a plasma source volume; generating a high density plasma in said source volume; generating an axial magnetic field directed from the source volume and expanding gradually through the second end; and establishing an electric double layer between the source volume and said second end.
  • the plasma beam generator is used as a spacecraft plasma thruster.
  • the containment vessel is a ceramic tube such as for example a glass tube.
  • the plasma beam generator preferably operates by electrostatic, inductive or helicon coupling.
  • the plasma generator includes an antenna enveloping the containment vessel.
  • the antenna preferably is supplied with radio frequency power via a matching network.
  • the magnetic field is generated by one or more solenoids surrounding the containment vessel at selected locations.
  • the magnetic field preferably has a strength of a few hundred gauss in the plasma source volume.
  • the present invention provides an apparatus and method for producing and extracting a high density plasma without external electron neutralisers or excessive radiation loss as well as providing a high electrical efficiency with a low system mass.
  • the double layer separates the plasma in the source and the plasma diffusing to space that provides the thrust. It is currently thought that the double layer exists when the mean free paths for the most important collisions is greater than the system dimension. Its thickness is of the order of or less than millimetres and its amplitude can typically be 30 to 50 volts, allowing ions to be freely accelerated to the vacuum of space. Using a 15 cm diameter containment vessel, the expected maximum gas flow at 1 milliTorr is 3.6 x 10 19 sec "1 for Argon which if completely ionised and accelerated to 50 eV by the source/double layer ensemble would represent a thrust of 66 mN (milliNewtons).
  • Figure 1 is a schematic diagram of a spacecraft powered by a plasma thruster according an embodiment of the present invention
  • Figure 2 is a schematic diagram of an embodiment of the present invention and an experimental arrangement to measure its operation
  • Figure 3 is graph of the axial direct current magnetic field along the axis of the apparatus shown in Figure 2;
  • Figure 4 is a graph of the plasma potential along the axis of the apparatus shown in Figure 2.
  • Figure 5 is a graph of the plasma density along the axis of the apparatus shown in Figure 2.
  • a plasma thruster 1 has a containment vessel 2 formed by a glass tube 3 of 15cm diameter and 30 cm long.
  • a first end 4 of the vessel 2 is closed by a glass plate 5 and the other end 6 of the vessel 2 opens into a 32 cm diameter earthed aluminium diffusion chamber 7.
  • a gas inlet 8 extends through the glass plate 5 to supply a plasma producing gas from a reservoir 9 (see Figure 1) to a first end of the containment vessel 2.
  • a plasma generator 10 is formed by a helicon antenna 11 which envelops the vessel 2 and supplied via a radio frequency generator 12 operating at a frequency of 13.6 MHz by directional coupler 13 and matching circuit 14.
  • Solenoids 15, 16 are provided around the vessel 2 at either end of the vessel 2 and energised from a power supply 17 (shown in Figure 1) to provide a gradually expanding axial direct current magnetic field of up to a few hundred gauss. In space power consumption could be minimised if the thermal design allows copper and solenoids to cool to around 200°k thereby reducing the resistance by a factor of five and the power drain to a few tens of watts.
  • Figure 3 is a graph of axial direct current magnetic field along the axis of the apparatus shown in Figure 2 in experiments performed, starting at one edge of the glass plate 5 to 60 cm at the remote end of the diffusion chamber 7.
  • a scale is shown in Figure 2.
  • the field gradually expands from about 250 G within the vessel 2 to a few tens of gausses in the diffusion chamber 7.
  • Open end 6 of vessel 2 is contiguously attached to the diffusion chamber 7 which is provided with a pumping system 18 connected to the sidewall of the diffusion chamber 7 to simulate the vacuum of space.
  • An energy analyser probe 19 and an L-shaped single Langmuir probe 20 are movable axially in the diffusion chamber 7 and into the vessel 2 to measure plasma potential and ion energy.
  • Figure 4 and Figure 5 are graphs of the plasma potential and plasma density respectively, along the apparatus shown in Figure 2 starting at 0 cm at one edge of the glass plate 5 to 60 cm at the remote end of diffusion chamber 7, for the conditions of the axial direct current magnetic field shown in Figure 3, and the pressure in the vessel 2 and the diffusion chamber 7 maintained at substantially 0.2 milliTorr. Again, the scale is shown in Figure 2.
  • the plasma potential measurements were obtained with the energy analyser probe 19 along the z-axis of the apparatus shown in Figure 2 during one run for increasing values of z, starting in the centre of the plasma source in the vessel 2.
  • the energy analyser probe 19 measurements were made on-axis with the entrance orifice of the energy analyser probe 19 facing radially. It is thought that the energy analyser probe 19 has an energy resolution of 1.0 eV or better.
  • the interpretation of energy analyser probe 19 measurements however, can be difficult in a flowing plasma, especially in the present case, in which the flow is very supersonic. While it is believed the energy analyser probe 19 provides a relatively accurate measure of the local plasma potential, the radially oriented energy analyser probe 19 could underestimate the plasma density since it would not collect all the ions accelerated by the electric field of the expanding plasma.
  • the graph of Figure 4 shows that the electric field in the plasma source generated in the vessel 2 is reasonably constant along the axis of the vessel 2 and is equal to about 220 V m "1 .
  • the mean free path for charge exchange is about 30 cm at 0.2 milliTorr, it is expected a large proportion of ions would be accelerated to at least 20 eV, which is highly supersonic.
  • the electron temperature determined from the Langmuir probe 20 is measured to be 8 ⁇ 0.5 eV in the diffusion chamber 7, which is what would be expected at this pressure. In the source, the fit of the electron current gives an electron temperature of 10 ⁇ 0.5 eV.
  • V p - V f where V p is the plasma potential and V f is the floating potential, is approximately 5.2T e for an Argon plasma
  • the electron temperature upstream of the double layer is about 25% greater than downstream.
  • the existence of a density dip is also noted on the low-potential side of the double layer. Although precise density measurements were not possible on-axis, the potential measurements were sufficient to characterise the type of double layer as current- free, with e ⁇ /kT ⁇ 3, using the potential drop of 25 V adjacent the exit of the vessel 2 and the downstream electron temperature of 8 eV.
  • the double layer thickness is less than 1 cm, corresponding to about 50 Debye lengths for a plasma density of 1 X 10 10 cm '3 , making this a relatively narrow double layer.
  • the thrust generated by this system which is defined as the rate of change of momentum, can simply be calculated from the plasma density and the potential drop (including in the vessel 2), along with an estimate of the ion energy gain before charge exchange.
  • This thrust is limited by the gas flow, and therefore the pump from the gas reservoir (not shown), and the power being put into the plasma.
  • the exit of the vessel 2 can be regarded as a black hole that would increase the gas flow by a factor of around 100.
  • the plasma density in these sources generally increases linearly with the power, so it is expected that densities of over 10 12 cm '3 can be generated.
  • this simple configuration can be developed to be a plasma thruster operating in space conditions with a thrust of some hundreds of mN.
  • this phenomenon can also be of use in the surface processing industry, where a flux of energetic ions that is uniform over a large area can have various applications.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Remote Sensing (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Plasma Technology (AREA)

Abstract

L'invention concerne un générateur (1) de faisceau de plasma à charge neutre, qui comporte un récipient (2) de confinement qui a une première extrémité (4) et une seconde extrémité (6) et qui définit un volume source de plasma. La seconde extrémité (6), ouverte, permet l'expulsion du plasma. Une entrée de gaz (8), contiguë à la première extrémité (4), permet l'alimentation en gaz producteur de plasma, et un générateur (10) de plasma produit un plasma neutre de densité élevée dans le volume source. Un générateur de champ magnétique (15, 16) produit un champ magnétique axial conduit à partir du volume source et s'étendant progressivement par la seconde extrémité (6). Une double couche électrique est placée entre le volume source et la seconde extrémité.
PCT/AU2003/000763 2002-06-19 2003-06-19 Generateur de faisceau de plasma Ceased WO2004002201A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003232523A AU2003232523A1 (en) 2002-06-19 2003-06-19 A plasma beam generator

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPS3033A AUPS303302A0 (en) 2002-06-19 2002-06-19 A plasma beam generator
AUPS3033 2002-06-19

Publications (1)

Publication Number Publication Date
WO2004002201A1 true WO2004002201A1 (fr) 2003-12-31

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PCT/AU2003/000763 Ceased WO2004002201A1 (fr) 2002-06-19 2003-06-19 Generateur de faisceau de plasma

Country Status (2)

Country Link
AU (1) AUPS303302A0 (fr)
WO (1) WO2004002201A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012042143A1 (fr) 2010-09-30 2012-04-05 Astrium Sas Procédé et dispositif pour la formation d'un faisceau plasma

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0785996A (ja) * 1993-09-20 1995-03-31 Nichimen Denshi Koken Kk Ｅｃｒプラズマ発生装置
JPH11251090A (ja) * 1998-03-02 1999-09-17 Foi:Kk プラズマ発生装置
US6334302B1 (en) * 1999-06-28 2002-01-01 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Variable specific impulse magnetoplasma rocket engine

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0785996A (ja) * 1993-09-20 1995-03-31 Nichimen Denshi Koken Kk Ｅｃｒプラズマ発生装置
JPH11251090A (ja) * 1998-03-02 1999-09-17 Foi:Kk プラズマ発生装置
US6334302B1 (en) * 1999-06-28 2002-01-01 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Variable specific impulse magnetoplasma rocket engine

Non-Patent Citations (8)

* Cited by examiner, † Cited by third party
Title
"3.1 Laboratory experiments: Electron waves excited at an electric double layer", DIVISION OF PLASMA PHYSICS, ALFVEN LABORATORY ROYAL INSTITUTE OF TECHNOLOGY, 1995, Retrieved from the Internet <URL:http://www.plasma.kth.se/alp/annrep-1995.html> [retrieved on 20030730] *
COADA D. ET AL.: "On the spontaneous generation of coherent complex structures and slef-sustained periodical phenomena in plasma", ROMANIAN REPORTS IN PHYSICS, vol. 54, no. 1-5, 2002, pages 205 - 210 *
DATABASE WPI Derwent World Patents Index; Class L03, AN 1999-576784/49 *
DATABASE WPI Derwent World Patents Index; Class U11, AN 1995-164893/22 *
GUNNELL H. ET AL.: "Bursts of high-frequency plasma waves at an electric double layer", JOURNAL OF PHYSICS D: APPLIED PHYSICS, vol. 29, 1996, pages 643 - 654 *
GUNNELL H. ET AL.: "Electric field spikes formed by electron beam-plasma interaction in plasma density gradients", PHYSICS OF PLASMAS, vol. 4, no. 8, August 1997 (1997-08-01), pages 2805 - 2812 *
MASLOV V.I.: "Double layer as a plasma lens for focusing of charged particle beams", DIVISION OF PLASMA PHYSICS MEETING 97 PROGRAM, 17 November 1997 (1997-11-17) - 21 November 1997 (1997-11-21), PITTSBURGH, Retrieved from the Internet <URL:http://flux.aps.org/meetings/YR97/BAPSDPP97/> [retrieved on 20030730] *
PHYSICAL MODEL, TECHNION PHYSICS DEPARTMENT, PLASMA LABORATORY, Retrieved from the Internet <URL:http://physics.technion.ac.il/~konst/Notes/Physical%20model> [retrieved on 20030730] *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012042143A1 (fr) 2010-09-30 2012-04-05 Astrium Sas Procédé et dispositif pour la formation d'un faisceau plasma

Also Published As

Publication number Publication date
AUPS303302A0 (en) 2002-07-11

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