Patents by Inventor Tihiro Ohkawa

Tihiro Ohkawa 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: 5125104
    Abstract: A compact transmitting device located in an exploding projectile transmits an RF pulse upon explosion of the projectile. Receipt of the RF pulse, through triangulation or equivalent techniques, identifies the burst point of the projectile. The transmitting device comprises a magnetic circuit that includes a permanent magnet, a ferromagnetic core having an air gap some distance from the permanent magnet, and a coil in the air gap. Stored energy in the permanent magnet is converted into a high power electrical pulse when the permanent magnet is destroyed. Prior to destruction of the magnet, a constant high magnetic flux exists in the air gap, but induces no current in the coil because it is a constant flux. Upon destruction of the permanent magnet, the magnetic flux changes rapidly, causing a high power electrical pulse to be generated.
    Type: Grant
    Filed: May 9, 1990
    Date of Patent: June 23, 1992
    Assignee: General Atomics
    Inventor: Tihiro Ohkawa
  • Patent number: 5117188
    Abstract: A magnet system used for magnetic resonance imaging comprises a magnetic coil energizable to establish a magnetic field and a contoured insert of ferromagnetic material positioned within the coil. The insert is substantially dish-shaped and has a top surface contoured with radial transitions from a flat portion, to a concave portion, to a convex portion, to provide a uniform magnetic field within a target zone located at the center of the front surface. A method is also disclosed for determining the proper contour to achieve high uniform magnetic field within the target zone.
    Type: Grant
    Filed: October 29, 1990
    Date of Patent: May 26, 1992
    Assignee: General Atomics
    Inventor: Tihiro Ohkawa
  • Patent number: 5095271
    Abstract: A nuclear magnetic resonance device has a hollow cylindrical magnet that forms a void. The magnet has a plurality of south poles and an equal plurality of north poles, the poles being dimensioned and disposed on the magnet to establish a toroidal zone external to the magnet wherein the field of the magnet is of substantially constant strength. A solenoidal antenna is positioned within the void of the magnet. Electrical insulating material is positioned to cover the bases of the combined cylindrical structure and may also be disposed between the antenna and the magnet. Associated electronic power, signal processing, and indicating equipment may then be mounted adjacent the electrical insulator and the entire assembly contained in a suitable housing.
    Type: Grant
    Filed: May 14, 1990
    Date of Patent: March 10, 1992
    Assignee: General Atomics
    Inventor: Tihiro Ohkawa
  • Patent number: 5068543
    Abstract: Potentially harmful electromagnetic radiation associated with high voltage power transmission lines is reduced or minimized by splitting the current delivered to a load between at least three conductors, and by maintaining a specific spatial relationship between the respective conductors. Single phase transmission at reduced radiation may occur using three or four conductors spatially positioned, as viewed in a cross sectional plane, in a horizontal line or a rectangular array, respectively. Three phase transmission at reduced radiation may occur using five or six conductors spatially positioned in the corners of a rectangular array, with one conductor in the center, or a hexagonal array, respectively.
    Type: Grant
    Filed: November 14, 1990
    Date of Patent: November 26, 1991
    Assignee: General Atomics
    Inventor: Tihiro Ohkawa
  • Patent number: 5057489
    Abstract: A multifilamentary superconducting cable has two parallel spaced-apart guide wires. A first layer of mutually parallel superconducting filaments is woven partially around and between the guide wires in a transposed braid. Likewise, a second layer of mutually parallel superconducting filaments is woven partially around and between the guide wires in a transposed braid. Thus, the two layers overlap each other as the respective layers pass between the guide wires. The two superconducting layers and two guide wires are enclosed in a helical copper duct, with the guide wires being oriented within the duct.
    Type: Grant
    Filed: September 21, 1990
    Date of Patent: October 15, 1991
    Assignee: General Atomics
    Inventors: Tihiro Ohkawa, Robert A. Olstad
  • Patent number: 5026683
    Abstract: A superconducting wire and a process for fabricating such a wire. The present invention relates specifically to the fabrication of a wire using a ceramic superconducting material. Initially, a quantity of highly pure high temperature superconducting material is obtained. The superconducting material may be fabricated by any one of a number of known fabrication methods such as by aqueous coprecipitation, conventional sol gel techniques or solid state reaction processes.Once a ceramic superconducting material in particulate form is obtained, surface impurities on the particles are removed. One such surface cleaning procedure is known as "sputtering." Sputtering strips the surface atoms from the surface of the superconducting material, leaving only pure superconducting ceramic.The superconductive ceramic produced according to the procedure outlined above is then used in the formation of a superconducting wire.
    Type: Grant
    Filed: October 27, 1988
    Date of Patent: June 25, 1991
    Assignee: General Atomics
    Inventor: Tihiro Ohkawa
  • Patent number: 5023109
    Abstract: Synthetic diamond crystals and films are deposited on a pair of uniformly spaced apart facing plates made of silicon, molybdenum or boron in elemental, nitride or carbide form. The plates are suitably supported within a totally thermally insulated chamber where a pressure of about 10 torr or less is maintained in the form of an atmosphere which includes a carbon source and a major portion of hydrogen, and preferably includes oxygen in equal amount to the carbon. By supplying sufficient microwave power to create a plasma and a uniform temperature of about 950.degree. C. at the plate surfaces, diamond crystals economically grow on the surfaces of the facing plates. Preferably, either the plates or the backing sections thereof have a relatively high thermal conductivity so as to maintain a uniform temperature across the entire plate surface areas.
    Type: Grant
    Filed: September 6, 1989
    Date of Patent: June 11, 1991
    Assignee: General Atomics
    Inventors: Jack Chin, Robert R. Goforth, Tihiro Ohkawa
  • Patent number: 4948497
    Abstract: An apparatus to acoustically fluidize a bed of fine particles comprises a generally box-shaped hollow chamber. An acoustic source is located at the bottom of the chamber and a convection inhibiting heater is located at the top of the chamber. An acoustic wave is directed from the source into the chamber to levitate and suspend fine particles within the chamber at determinable distances from the acoustic source according to the intensity and frequency of the acoustic wave.
    Type: Grant
    Filed: May 18, 1988
    Date of Patent: August 14, 1990
    Assignee: General Atomics
    Inventor: Tihiro Ohkawa
  • Patent number: 4745336
    Abstract: The present invention provides a vircator with improved efficiency. An elongated anode is aligned with an elongated cathode so as to produce an elongated virtual cathode when a direct current voltage source is electrically connected to the elongated cathode. A surface wave having a velocity near the velocity of light will be produced on the virtual cathode. Waveguide means enclosing the virtual cathode is disposed so as to propagate microwave radiation in a direction parallel to the direction of elongation of the cathode, anode and virtual cathode. The waveguide is designed to match the phase velocity of the microwave to the velocity of the virtual cathode surface wave.
    Type: Grant
    Filed: May 27, 1986
    Date of Patent: May 17, 1988
    Assignee: GA Technologies Inc.
    Inventor: Tihiro Ohkawa
  • Patent number: 4734246
    Abstract: A toroidal fusion device with an elongated axial cross section is described which is capable of ignition without auxiliary heating and with modest toroidal magnetic field. The device is based on the principle that for elongated toroids the toroidal current density in the plasma at ignition is subject to a limit which is proportional to the product of the elongation and the toroidal magnetic field. The elongation is made greater than about 4. The aspect ratio is preferably between about 3 and 10.
    Type: Grant
    Filed: January 28, 1985
    Date of Patent: March 29, 1988
    Assignee: GA Technologies Inc.
    Inventors: Tihiro Ohkawa, Ming Chu, Peter A. Politzer, Reagan W. Moore
  • Patent number: 4723250
    Abstract: A solid state cyclotron laser device generate coherent electromagnetic radiation. A semiconductor configuration comprises an emitter region and a collector region separated by a base region and barrier layers on each side of the base. The semiconductor configuration is biased such that electrons enter the base region from the emitter region as hot electrons. A magnetic field applied by an external source to the base region causes the hot electrons to gyrate and quantize into Landau levels. An optical resonance cavity produces standing wave modes which stimulate the electrons to move from higher to lower Landau levels to generate conherent radiation. Electrons with decreased energy are removed at the collector in order to maintain the population inversion. The device is tunable by adjusting the magnetic field.
    Type: Grant
    Filed: December 20, 1985
    Date of Patent: February 2, 1988
    Assignee: GA Technologies Inc.
    Inventors: Tihiro Ohkawa, Yuh-Ren Lin-Liu, Hiroyuki Ikezi
  • Patent number: 4710339
    Abstract: Plasma including plasma ions is magnetically confined by a magnetic field. The plasma has a defined outer surface and is intersected by resonance surfaces of respective common ion cyclotron frequency of a predetermined species of plasma ions moving in the magnetic field. A radio frequency source provides radio frequency power at a radio frequency corresponding to the ion cyclotron frequency of the predetermined species of plasma ions moving in the field at a respective said resonance surface.
    Type: Grant
    Filed: August 27, 1984
    Date of Patent: December 1, 1987
    Assignee: The United States of America as represented by the United States Department of Energy
    Inventor: Tihiro Ohkawa
  • Patent number: 4688227
    Abstract: A method of cooling an electron beam with electrons having energies in excess of 10 MeV by directing a cooling laser beam over the path of the electron beam so as to achieve Compton scattering interactions, and a device which utilizes this method with other elements to produce a free electron laser system having much greater efficiencies than a single pass free electron laser.
    Type: Grant
    Filed: September 16, 1985
    Date of Patent: August 18, 1987
    Assignee: GA Technologies Inc.
    Inventors: Vincent S. Chan, Shiu-Chu Chiu, Tihiro Ohkawa
  • Patent number: 4665412
    Abstract: A superlattice quantum well device comprising a first set of conductive layers and a second set of conductive layers having discrete electronic energy levels different from those of the first set of layers, separated by relatively nonconductive insulation layers.
    Type: Grant
    Filed: June 19, 1985
    Date of Patent: May 12, 1987
    Assignee: GA Technologies Inc.
    Inventors: Tihiro Ohkawa, Lawrence D. Woolf
  • Patent number: 4560528
    Abstract: A magnetic well reversed field plasma pinch method and apparatus produces hot magnetically confined pinch plasma in a toroidal chamber having a major toroidal axis and a minor toroidal axis and a small aspect ratio. A reversed magnetic field pinch current channel within the plasma and at least one hyperbolic magnetic axis outside substantially all of the plasma form thereby a region of average magnetic well in a region of nested closed magnetic surfaces surrounding the plasma current channel when the magnetic field component in the direction of the hyperbolic magnetic axis is also made to be substantially less than zero in the vicinity of the hyperbolic magnetic axis. The magnetic well reversed field pinch is operated so that reversal of the safety factor q and of the toroidal magnetic field takes place within the plasma, and the plasma so produced closely approximates known theoretical stability conditions.
    Type: Grant
    Filed: April 12, 1982
    Date of Patent: December 24, 1985
    Assignee: GA Technologies Inc.
    Inventor: Tihiro Ohkawa
  • Patent number: 4543231
    Abstract: A multipole plasma pinch method and apparatus produces hot magnetically confined z-pinch plasma with a plurality of z-pinch current channels arranged so as to generate a multipolar magnetic field and at least one hyperbolic magnetic axis within the plasma space roughly enclosed by the channels, forming thereby a region of average magnetic well in a region of nested closed plasma magnetic surfaces surrounding the plasma current channels, when the magnetic field component in the direction of the hyperbolic axis is also made to be substantially zero in the vicinity of the hyperbolic axis. The multipole pinch invention may be operated so that q and field reversal take place within the plasma, and the plasma so produced closely approximates known theoretical stability conditions. The well-producing hyperbolic axis of the present invention is produced effectively by replacing the solid conducting rings of prior art multipole plasma confinement devices by z-pinch-like toroidal current channel loops of plasma.
    Type: Grant
    Filed: December 14, 1981
    Date of Patent: September 24, 1985
    Assignee: GA Technologies Inc.
    Inventor: Tihiro Ohkawa
  • Patent number: 4354998
    Abstract: A method and apparatus for clearing thermal barrier regions of trapped ions in a tandem mirror fusion reactor apparatus utilizing a bend at each end of the cylindrical plasma chamber within which bend the thermal barrier is positioned. Ions trapped in said thermal barrier are caused by said bend to drift in a direction perpendicular to the incident magnetic field and the direction of centrifugal force, such that said ions are enabled to be collected in a divertor positioned along said ion drift path.
    Type: Grant
    Filed: September 17, 1979
    Date of Patent: October 19, 1982
    Assignee: General Atomic Company
    Inventor: Tihiro Ohkawa
  • Patent number: 4352722
    Abstract: A photovoltaic-electrolytic unit is provided to produce an electric current from solar energy and utilize the current to produce hydrogen by the electrolysis of water. The unit floats in an aqueous medium so that photoelectric cells are exposed to solar radiation, and electrodes submerged in the medium produce oxygen which is vented and hydrogen which is collected in the unit.
    Type: Grant
    Filed: March 12, 1981
    Date of Patent: October 5, 1982
    Assignee: General Atomic Company
    Inventor: Tihiro Ohkawa
  • Patent number: 4305783
    Abstract: Tokamak apparatus includes a pressure vessel for defining a reservoir and confining liquid therein. A toroidal liner disposed within the pressure vessel defines a toroidal space within the liner. Liquid metal fills the reservoir outside said liner. Electric current is passed through the liquid metal over a conductive path linking the toroidal space to produce a toroidal magnetic field within the toroidal space about the major axis thereof. Toroidal plasma is developed within the toroidal space about the major axis thereof.
    Type: Grant
    Filed: February 28, 1979
    Date of Patent: December 15, 1981
    Assignee: The United States of America as represented by the United States Department of Energy
    Inventors: Tihiro Ohkawa, Michael J. Schaffer
  • Patent number: 4305784
    Abstract: A tokamak apparatus includes a pressure vessel for defining a reservoir and confining liquid therein. A collapsible toroidal liner disposed within the pressure vessel defines a toroidal space within the liner. Liquid metal fills the reservoir outside said liner. A toroidal magnetic field is developed within the toroidal space about the major axis thereof. A toroidal plasma is developed within the toroidal space about the major axis thereof. Pressure is applied to the liquid metal to collapse the liner and reduce the volume of the toroidal space, thereby increasing the toroidal magnetic flux density therein.
    Type: Grant
    Filed: February 28, 1979
    Date of Patent: December 15, 1981
    Assignee: The United States of America as represented by the United States Department of Energy
    Inventor: Tihiro Ohkawa