US3032490A - Destruction of neutral particles in a device for producing a high density plasma - Google Patents

Destruction of neutral particles in a device for producing a high density plasma Download PDF

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Publication number
US3032490A
US3032490A US732770A US73277058A US3032490A US 3032490 A US3032490 A US 3032490A US 732770 A US732770 A US 732770A US 73277058 A US73277058 A US 73277058A US 3032490 A US3032490 A US 3032490A
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ions
plasma
ion
current
atomic
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US732770A
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Simon Albert
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Priority to US732770A priority Critical patent/US3032490A/en
Priority to GB10806/59A priority patent/GB869344A/en
Priority to FR792994A priority patent/FR1222257A/fr
Priority to CH359492D priority patent/CH359492A/fr
Priority to DEU6157A priority patent/DE1090346B/de
Priority to NL238636A priority patent/NL122955C/xx
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21B—FUSION REACTORS
    • G21B1/00—Thermonuclear fusion reactors
    • 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
    • H05H1/02—Arrangements for confining plasma by electric or magnetic fields; Arrangements for heating plasma
    • H05H1/22—Arrangements for confining plasma by electric or magnetic fields; Arrangements for heating plasma for injection heating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/10—Nuclear fusion reactors

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  • This invention relates to a novel method and apparatus for burning ou neutral particles in a region where a plasma is to be formed and contained such, for example, as disclosed in co-pending application Serial No. 728,754, filed April 15, 1958, entitled, Method and Apparatus for Trapping Ions in a Magnetic Field, by John S. Luce, and the present invention is an improvement over the system of this co-pending application.
  • high-energy molecular ions are injected into a confining magnetic field perpendicular to the lines of magnetic force. At some point in the orbit of these ions in the magnetic field, a portion of them are caused to dissociate and/or ionize to form atomic ions. These resultant atomic ions have one-half the momentum of the original molecular ions and hence have one-half the radius of curvature in the field. If the center ofthe orbits of these atomic ions coincides with the axis of the magnetic field, the ions-will circulate in a ring.
  • the atomic ion orbit will precess about the point of origin of the atomic ion.
  • the ions will circulate until-a charge exchange occurs with one of the neutral gas atoms in the system.
  • any such device there are present, particularly at startup, a large number of residual neutral particles (-3x10 3 l0 particles per cm?) in the reaction vessel before any reaction is begun.
  • These neutral particles are gas molecules which remain in the device even after evacuation, since available vacuum pumps cannot, of course, create a perfect vacuum.
  • These neutral particles are at relatively low energies-(cold) compared to ions in the plasma, and are deleterious in that they will remove hot ions from the system through the charge exchange process.
  • the hot ion strikes a neutral and picks up an electron, thus becoming a fast neutral particle, while the original low-energy neutral thus becomes a cold ion.
  • FIG. 1 shows an example of a plasma generator in which the principle of this invention may be effected
  • FIG. 2 shows a graph of critical current curves for various pressure conditions in the device of FIG. 1.
  • FIG. 1 a device is shown in which high energy molecular ions are injected into a chamber normal to a containing magnetic field and high intensity arc, for igniting a plasma by trapping atomic ions in a manner fully described above.
  • the device of FIG. 1 comprises an outer cylindrical shell 10 with joining end walls 13 and 14.
  • End wall 13 has a circular opening to which a tubular member 17 is affixed.
  • Member 17 has an end closure member 19 in which the cathode 1 is fixedly mounted.
  • End wall 14 has a circular opening to which is afiixed a tubular member 18.
  • Member 18 has an end closure 20 in which the anode ,2 is fixedly mounted.
  • Outer shell 10 is provided with a circular opening to which is attached a tubular member 21 which in turn has affixed thereto an end closure member 22.
  • Tubular member 21 Fixedly mounted in said member 22 is tubular member 23, provided with a reduced portion which connects with an aperture in liner '7.
  • a conventional ion accelerator tube 29 communicates with member 23, and serves to accelerate molecular ions from an external ion source 24 to relatively high energies.
  • the accelerator tube may be energized by a conventional high voltage generator.
  • a suitable high current source of ions may be provided by apparatus'such as Set forth on page 18 of Nucleonics,
  • Liner 7 has a pair of circular openings in alignment with a pair of circular openings in outer shell 10. The aligned openings are. joined by insulating bushings 25 and 26, respectively.
  • the inner chamber, formed by liner 7 and walls 27 and 28, is connected to a vacuum through openings 15 and 16 of bushings 25 and 26, respectively.
  • Outer liner 10 also has a pair of additional openings 11v and 12 connected to a vacuum, said openings being connected to an outer chamber located between the shell 10 and inner liner 7.
  • netic mirror coil is mounted .on apertured wall 8 and is disposed around the outside of inner liner 7 between the ion source tube 23 and bushing 25.
  • Another circular magnetic mirror coil 6 is mounted on apertured wall 9 and is disposed around the outside of inner liner 7 between ion source tube 23 and bushing 26.
  • a high intensity are discharge is initiated between the cathode and anode electrodes in a conventional manner.
  • the inside and outside chambers are evacuated and the pressure of the inside chamber is maintained at. approximately mm. Hg, while the outside chamber pressure is maintained at approximately 10- mm. Hg, for example.
  • the mirror coils 5 and 6 have an inside diameter of. 17 inches and a spacing between the inner faces of the coils of 18% inches. With these dimensions, a cylinder can be inscribed whose rims just touch the inner edge of the coils and the volume of such a cylinder is then equal to 69x10 cm.
  • the plasma which is formed by dissociation of the.
  • the gas used for the ion source input is deuterium, and the injection voltage of the molecular ions is approximately 500 kev., for example, which results in atomic ions of substantially 250 kev. energy.
  • the device of FIG. 1 at startup will have large numbers of neutral particles in it, and these neutral particles will remove hot ions from the system because of the charge exchange process.
  • the cross section for charge exchange is a steeply decreasing function of the atomic ion velocity above about 30 kev.
  • n atomic ion density
  • I atomic ion current
  • S surface of area of plasma
  • N density of neutrals in external, manifold, which is substantially 3X10 pressure in mm.
  • V volume occupiedby the plasma
  • v velocity of ions
  • the charge-exchange cross section values may be taken from the measured values published in Physical Review 103, 896, (1956) assuming for deuteron that the cross section is the same at the same relative volocity.
  • the value. is 5.5. 10- cm. at 50 kev., for example.
  • the ionization cross section values may be computed from the formula given by Bethe and Ashkin, Experimental Nuclear Physics, vol. 1, part II, published in 1953. The value is 1.0 lO- cm. at 250 kev., for example.
  • the coulomb cross section values may be computed from the formula where e is the charge on the electron, and E is the average energy of an ion in the plasma.
  • the first term on the right represents the constant source input; the second term takes into account mirror losses; and the third term represents loss by charge exchange.
  • the first term on the right represents the streaming of neutrals into the plasma; the second term represents the out-streaming from the plasma; and the third term shows the effects of neutral burnout by ionization and charge exchange.
  • the input current I used herein is the value of atomic ion current produced as a result of dissociation and/ or ionization of the molecular ion beam. If the critical value of molecular ion current is desired, the value of 1 obtained in Equation 3 must be multiplied by a factor proportional to the break up efficiency of the arc. For normal operation at 150 volts, 300 amperes, this (factor is 25%. Since the neutral in-streaming varies linearly with pressure, the value of critical current also varies linearly with pressure.
  • 01 is 1.0 1()- cm.
  • o' is 5.5 l0 cm.
  • N is about 3x10
  • the injection atomic ion energy is 250 kev. and the molecular ion energy is 500 kev.
  • the critical ratio I /I from Formula 3 above can be determined by substituting the values of w and a as given above, into the formula.
  • the value of 1 can be determined by multiplying the measured value of the injected molecular ion current by the known break-up efficiency of the arc discharge. For example, a molecular ion current of 80 ma., with an arc break-up efliciency of 25%, would produce an atomic ion current of 20 ma.
  • Equations 1 and 2 For a given pressure and energy, all of the parameters in Equations 1 and 2 above are known and are fixed for a given machine, except n and n which vary as 1 is varied. Since the value of 1 can be determined, as discussed above, the values of n and n can be determined by solving the two diflerential Equations 1 and 2 for each value of 1 For the same energy and a different pressure, the value of N will change since it varies linearly with the pressure as set forth above, and is substantially 3X10 times the pressure in mm. Hg. Therefore, it can be seen that n and n can be determined for different values of 1 for different selected pressures for plotting the curves shown in FIG. 2.
  • Equation 3 when solved, agrees with the results of Equations 1 and 2, as plotted on FIGURE 2. It can thus be seen that use of Equation 3 is a more direct way of obtaining the value of I for a given machine operating at a given energy and pressure. 5
  • the value of the critical atomic ion input current in any machine of this type can be controlled in at least four ways.
  • the current of molecular ions can be varied by changing the conditions in the ion source, such as by varying the source are voltage for example and thus changing the quantity of the injected molecular ions.
  • the injection voltage of the ion source may be varied and thus varying the energy of the injected molecular ions.
  • the value of the critical atomic ion current can be controlled by changing the break up efficiency of the mechanism causing ionization and/or dissociation of the molecular ion beam. If an arc is being used, a change in voltage or current of the are changes the percentage of atomic ions formed.
  • a fourth control over the value of the critical atomic ion current can be effected by changing the pressure within the plasma chamber.
  • a plasma can be formed in a portion of a stellarator-type machine by providing one section with temporary magnetic mirrors. The plasma, once formed, would be permitted to fill a larger portion of the machine by gradually moving the mirrors outward from each other. The high energy injection, if the input current is sufficiently large will cause burnout of the neutrals in such a machine. Once burnout has been achieved, the competing charge exchange process is eliminated and hot ions will collide with cold electrons, heating the electrons.
  • V In a method of forming a plasma trapped within a magnetic field by evacuating a region within said field,
  • the current of neutral particles I entering said field being directly proportional to the pressure therein, injecting molecular ions of deuterium at substantially 500 kev. into said field, and dissociating said ions With an energetic arc discharge to form a current of I substantially 25-0 kev.
  • the improved method for heating the cold ions and electrons associated with said atomic ions comprising establishing within said field an atomic ion current to neutral particle ratio 1 /1 of at least .05 2, whereby neutral particles are removed by said atomic sms f te t n the nt id re ion Th meth of l m 1 ere ai pr s ur ithin said region is substantiallylod mm, Hg and said current I is at least 8 milliamperes.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Plasma Technology (AREA)
  • Particle Accelerators (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US732770A 1958-04-28 1958-04-28 Destruction of neutral particles in a device for producing a high density plasma Expired - Lifetime US3032490A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US732770A US3032490A (en) 1958-04-28 1958-04-28 Destruction of neutral particles in a device for producing a high density plasma
GB10806/59A GB869344A (en) 1958-04-28 1959-03-31 Destruction of neutral particles in thermonuclear reactors
FR792994A FR1222257A (fr) 1958-04-28 1959-04-23 Procédé de destruction de particules neutres dans les réacteurs thermonucléaires
CH359492D CH359492A (fr) 1958-04-28 1959-04-28 Procédé de formation d'un plasma
DEU6157A DE1090346B (de) 1958-04-28 1959-04-28 Verfahren zum Ausbrennen neutraler Teilchen und zum Aufbau eines Plasmas in einer Reaktionskammer
NL238636A NL122955C (fr) 1958-04-28 1959-04-28

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US732770A US3032490A (en) 1958-04-28 1958-04-28 Destruction of neutral particles in a device for producing a high density plasma

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CH (1) CH359492A (fr)
DE (1) DE1090346B (fr)
FR (1) FR1222257A (fr)
GB (1) GB869344A (fr)
NL (1) NL122955C (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3160566A (en) * 1962-08-09 1964-12-08 Raphael A Dandl Plasma generator
US4584160A (en) * 1981-09-30 1986-04-22 Tokyo Shibaura Denki Kabushiki Kaisha Plasma devices
US20120229012A1 (en) * 2011-03-10 2012-09-13 Nissin Ion Equipment Co., Ltd. Ion source

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1370828A (fr) * 1963-07-19 1964-08-28 Commissariat Energie Atomique Perfectionnements à la purification d'un plasma

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2636990A (en) * 1949-12-14 1953-04-28 Atomic Energy Commission Ion source unit
US2826708A (en) * 1955-06-02 1958-03-11 Jr John S Foster Plasma generator
US2831996A (en) * 1956-09-19 1958-04-22 Eugene F Martina Ion source

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2636990A (en) * 1949-12-14 1953-04-28 Atomic Energy Commission Ion source unit
US2826708A (en) * 1955-06-02 1958-03-11 Jr John S Foster Plasma generator
US2831996A (en) * 1956-09-19 1958-04-22 Eugene F Martina Ion source

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3160566A (en) * 1962-08-09 1964-12-08 Raphael A Dandl Plasma generator
US4584160A (en) * 1981-09-30 1986-04-22 Tokyo Shibaura Denki Kabushiki Kaisha Plasma devices
US20120229012A1 (en) * 2011-03-10 2012-09-13 Nissin Ion Equipment Co., Ltd. Ion source
US8604683B2 (en) * 2011-03-10 2013-12-10 Nissin Ion Equipment Co., Ltd. Bucket-type ion source for fanning cusped magnetic fields inside a plasma generation chamber

Also Published As

Publication number Publication date
NL122955C (fr) 1967-09-15
NL238636A (fr) 1964-04-17
CH359492A (fr) 1962-01-15
DE1090346B (de) 1960-10-06
GB869344A (en) 1961-05-31
FR1222257A (fr) 1960-06-09

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