Patents by Inventor Nathaniel J. Fisch

Nathaniel J. Fisch has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6777862
    Abstract: An apparatus and method for thrusting plasma, utilizing a Hall thruster with segmented electrodes along the channel, which make the acceleration region as localized as possible. Also disclosed are methods of arranging the electrodes so as to minimize erosion and arcing. Also disclosed are methods of arranging the electrodes so as to produce a substantial reduction in plume divergence. The use of electrodes made of emissive material will reduce the radial potential drop within the channel, further decreasing the plume divergence. Also disclosed is a method of arranging and powering these electrodes so as to provide variable mode operation.
    Type: Grant
    Filed: April 13, 2001
    Date of Patent: August 17, 2004
    Assignee: General Plasma Technologies LLC
    Inventors: Nathaniel J. Fisch, Yevgeny Raitses
  • Patent number: 6448721
    Abstract: An apparatus and method for thrusting plasma, utilizing a Hall thruster with a cylindrical geometry, wherein ions are accelerated in substantially the axial direction. The apparatus is suitable for operation at low power. It employs small size thruster components, including a ceramic channel, with the center pole piece of the conventional annular design thruster eliminated or greatly reduced. Efficient operation is accomplished through magnetic fields with a substantial radial component. The propellant gas is ionized at an optimal location in the thruster. A further improvement is accomplished by segmented electrodes, which produce localized voltage drops within the thruster at optimally prescribed locations. The apparatus differs from a conventional Hall thruster, which has an annular geometry, not well suited to scaling to small size, because the small size for an annular design has a great deal of surface area relative to the volume.
    Type: Grant
    Filed: April 13, 2001
    Date of Patent: September 10, 2002
    Assignee: General Plasma Technologies LLC
    Inventors: Yevgeny Raitses, Nathaniel J. Fisch
  • Publication number: 20020014845
    Abstract: An apparatus and method for thrusting plasma, utilizing a Hall thruster with a cylindrical geometry, which is particularly suitable for operation at low power, such as under 125 Watts, and emptying small size thruster components. The disclosed apparatus differs from a conventional Hall thruster, which has an annular geometry. The conventional annular design is not well suited to scaling to small size, because the small size for an annular design has a great deal of surface area relative to the volume. The present invention discloses a cylindrical geometry Hall thruster, utilizing a ceramic channel, in which the center pole piece of the conventional annular design thruster is eliminated or greatly reduced. Also disclosed are means of accomplishing efficient operation of such a thruster by designing magnetic fields with a substantial radial component, such that ions are accelerated in substantially the axial direction.
    Type: Application
    Filed: April 13, 2001
    Publication date: February 7, 2002
    Inventors: Yevgeny Raitses, Nathaniel J. Fisch
  • Publication number: 20020008455
    Abstract: An apparatus and method for thrusting plasma, utilizing a Hall thruster with segmented electrodes along the channel, which make the acceleration region as localized as possible. Also disclosed are methods of arranging the electrodes so as to minimize erosion and arcing. Also disclosed are methods of arranging the electrodes so as to produce a substantial reduction in plume divergence. The use of electrodes made of emissive material will reduce the radial potential drop within the channel, further decreasing the plume divergence. Also disclosed is a method of arranging and powering these electrodes so as to provide variable mode operation.
    Type: Application
    Filed: April 13, 2001
    Publication date: January 24, 2002
    Inventors: Nathaniel J. Fisch, Yevgeny Raitses
  • Patent number: 5375149
    Abstract: An apparatus and method of extracting power from energetic ions produced by nuclear fusion in a toroidal plasma to enhance respectively the toroidal plasma current and fusion reactivity. By injecting waves of predetermined frequency and phase traveling substantially in a selected poloidal direction within the plasma, the energetic ions become diffused in energy and space such that the energetic ions lose energy and amplify the waves. The amplified waves are further adapted to travel substantially in a selected toroidal direction to increase preferentially the energy of electrons traveling in one toroidal direction which, in turn, enhances or generates a toroidal plasma current. In an further adaptation, the amplified waves can be made to preferentially increase the energy of fuel ions within the plasma to enhance the fusion reactivity of the fuel ions. The described direct, or in situ, conversion of the energetic ion energy provides an efficient and economical means of delivering power to a fusion reactor.
    Type: Grant
    Filed: July 26, 1993
    Date of Patent: December 20, 1994
    Assignee: The United States of America as represented by the United States Department of Energy
    Inventors: Nathaniel J. Fisch, Jean M. Rax
  • Patent number: 5120487
    Abstract: A method including externally imposing an impulsive momentum-space flux to perturb hot tokamak electrons thereby producing a transient synchrotron radiation signal, in frequency-time space, and the inference, using very fast algorithms, of plasma parameters including the effective ion charge state Z.sub.eff, the direction of the magnetic field, and the position and width in velocity space of the impulsive momentum-space flux, and, in particular, the dc toroidal electric field.
    Type: Grant
    Filed: March 1, 1990
    Date of Patent: June 9, 1992
    Assignee: The United States of America as represented by the United States Department of Energy
    Inventors: Nathaniel J. Fisch, Arnold H. Kirtz
  • Patent number: 4615861
    Abstract: Apparatus and method of the invention maintain a plasma current with an oscillatory nonohmic current drive. Each cycle of operation has a generation period in which current driving energy is applied to the plasma, and a relaxation period in which current driving energy is removed. Plasma parameters, such as plasma temperature or plasma average ionic charge state, are modified during the generation period so as to oscillate plasma resistivity in synchronism with the application of current driving energy. The invention improves overall current drive efficiencies.
    Type: Grant
    Filed: March 22, 1983
    Date of Patent: October 7, 1986
    Assignee: The United States of America as represented by the United States Department of Energy
    Inventor: Nathaniel J. Fisch
  • Patent number: 4425295
    Abstract: A system for the generation of toroidal current in a plasma which is prepared in a toroidal magnetic field. The system utilizes the injection of high-frequency waves into the plasma by means of waveguides. The wave frequency and polarization are chosen such that when the waveguides are tilted in a predetermined fashion, the wave energy is absorbed preferentially by electrons traveling in one toroidal direction. The absorption of energy in this manner produces a toroidal electric current even when the injected waves themselves do not have substantial toroidal momentum. This current can be continuously maintained at modest cost in power and may be used to confine the plasma. The system can operate efficiently on fusion grade tokamak plasmas.
    Type: Grant
    Filed: February 9, 1981
    Date of Patent: January 10, 1984
    Assignee: The United States of America as represented by the United States Department of Energy
    Inventors: Nathaniel J. Fisch, Allen H. Boozer
  • Patent number: 4423001
    Abstract: A system for the generation of toroidal current in a plasma which is prepared in a toroidal magnetic field. The system utilizes the injection of low-frequency waves into the plasma by means of phased antenna arrays or phased waveguide arrays. The plasma is prepared with a minority ion species of different charge state and different gyrofrequency from the majority ion species. The wave frequency and wave phasing are chosen such that the wave energy is absorbed preferentially by minority species ions traveling in one toroidal direction. The absorption of energy in this manner produces a toroidal electric current even when the injected waves themselves do not have substantial toroidal momentum. This current can be continuously maintained at modest cost in power and may be used to confine the plasma. The system can operate efficiently on fusion grade tokamak plasmas.
    Type: Grant
    Filed: February 9, 1981
    Date of Patent: December 27, 1983
    Assignee: The United States of America as represented by the United States Department of Energy
    Inventor: Nathaniel J. Fisch
  • Patent number: 4292124
    Abstract: A system for generating steady state confining current for a toroidal plasma fusion reactor providing steady-state generation of the thermonuclear power. A dense, hot toroidal plasma is initially prepared with a confining magnetic field with toroidal and poloidal components. Continuous wave RF energy is injected into said plasma to establish a spectrum of traveling waves in the plasma, where the traveling waves have momentum components substantially either all parallel, or all anti-parallel to the confining magnetic field. The injected RF energy is phased to couple to said traveling waves with both a phase velocity component and a wave momentum component in the direction of the plasma traveling wave components. The injected RF energy has a predetermined spectrum selected so that said traveling waves couple to plasma electrons having velocities in a predetermined range .DELTA.. The velocities in the range are substantially greater than the thermal electron velocity of the plasma.
    Type: Grant
    Filed: August 21, 1978
    Date of Patent: September 29, 1981
    Assignee: Massachusetts Institute of Technology
    Inventor: Nathaniel J. Fisch