Abstract: A photothermophotovoltaic energy conversion system converts solar energy to electrical energy and includes a radiator and a photovoltaic cell. The photovoltaic cell receives incoming energy, including solar energy, and converts a first portion of the incoming energy to electrical energy. The photovoltaic cell includes a reflector for reflecting a second portion of the incoming energy to the radiator to heat it. The heated radiator in turn radiates energy back to the photovoltaic cell for subsequent energy conversion therein of a first portion thereof. A second portion is reflected to the radiator, conserving heat.

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.

Abstract: A magnet system for providing a localized, substantially homogeneous field for use in medical magnetic resonance imaging and its incorporation into a method of siting. The magnet system includes a vacuum vessel defining a bore for receiving the subject of the imaging and having a first end and a second end. A cryogenic containment vessel is supported within the vacuum vessel and a single coil is disposed within the containment vessel for providing the magnetic field. The magnetic system also includes a shield assembly of ferromagnetic material positioned closely adjacent the outside of the vacuum vessel and including first and second end assemblies and a plurality of axially extending beam-like members interconnecting the end assemblies. The coil comprises a winding made up of thousands of turns of small superconductive wire and which is configured to compensate for the effect of the presence of the shield to provide the substantially homogeneous field at a predetermined location in the bore.

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.

Abstract: A magnetically confined helical z-pinch plasma is formed as a helicoid having an approximately D-shaped cross section, thereby generating a large transform of magnetic field line pitch suitably distributed throughout the plasma volume to aid in the reversal of field lines in the axial direction and increase magnetic shear.

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.

Abstract: The present invention is a device for generating high power microwave pulses using a nonlinear dispersive transmission line connected by a switch means to a source cable means and a high voltage source. The closing of the switch means sends an electrical pulse propagating from the source cable means through the transmission line. The pulse decomposes into a short, high power pulse of microwaves which consists of an array of solitons. The output of the line may be coupled into an antenna, wave guide or other load.

Abstract: An austentic steel component is fused to a ferritic steel component with a filler alloy specifically formulated to have a thermal coefficient of expansion similar to that of the ferritic steel, a creep rate intermediate between that of the ferritic and austenitic steels, a rupture strength at least as great as that of the ferritic steel, and a carbon activity intermediate that of the ferritic and austenitic steels. Suitable filler alloys have the following general compositions: (1) 1-3% nickel, 11-13% chromium, 1.6-2.0% molybdenum, 0.07-0.1% carbon, 0.5-0.9% manganese and 0-1.5% tungsten, balance iron, and (2) 41-56% nickel, 3.5-10.0% chromium, 1.6-2.5% molybdenum, 0.03-0.1% carbon and 0.5-2.0% manganese, balance iron.

Abstract: An electron gun for emitting a modulated electron beam. The gun includes an evacuated envelope having an output end with a photocathode positioned in the envelope and responsive to light to emit electrons. An anode is positioned between the photocathode and the output end for accelerating the electrons emitted by the photocathode. The gun further includes a source of potential interconnecting the anode and the photocathode for maintaining the anode electrostatically positive relative to the photocathode. A first laser provides a first laser beam at a first frequency illuminating the photocathode, and a second laser provides a second laser beam at a second frequency illuminating the photocathode at the same time. The first frequency differs from the second frequency by a beat frequency, whereby the photocathode provides the electron beam with the electrons spacially bunched in accordance with the beat frequency. A method of providing a modulated electron beam is also disclosed.

Abstract: In aiming a neutral particle beam cross hair sights are first lined up relative to a target, and then the beam is lined up with the cross hair sights. Blocking means is disposed in a particle beam so as to absorb, scatter and/or otherwise remove particles from the beam and thereby create a downstream shadow of predetermined size and shape in the beam. Shadow detecting means is disposed in the beam downstream of the blocking means and senses the particles and emits steering signals systematically related to the extent to which the shadow detecting means is in the shadow of the blocking means. Aligning means lines up the blocking means and the shadow means in a desired direction relative to the target. The steering signals are thus systematically related to the direction of the beam relative to the desired direction. The steering signal from the sensing means is used to direct the neutral particle beam to hit the target.

Abstract: A first wall structure for use in a fusion device surrounds the plasma region and includes a base wall which is substantially continuous. The base wall has an inner surface which faces the plasma region and an outer surface which faces the first wall coolant. The inner surface has a plurality of recesses. The wall structure also includes a number of inserts corresponding in number to the recesses with each insert being received in a respective recess and extending inwardly beyond the inner base wall surface. The inserts are made of material having a substantially greater heat flux capability than the material from which the base wall is formed. A method of forming a composite first wall structure for use in a fusion device, is also disclosed.

Abstract: Filament wound pressure tube has layers of filaments wound helically. The filaments of each such layer are disposed at an angle to a line parallel to the longitudinal axis of said tube which angle is approximately equal to a respective angle .theta. to the line, such angle .theta. being chosen such that the ratio sin.sup.2 .theta./r is approximately the same for all layers, where r is the radial distance from said axis to the location of such layer.

Abstract: A magnet system for providing a localized, substantially homogeneous magnetic field for use in nuclear magnetic resonance imaging. The magnet system includes a vacuum vessel defining a bore for receiving the subject of the imaging. It further includes a cryogenic containment vessel supported within the vacuum vessel. A single coil or "simple" solenoid is positioned within the containment vessel for providing the magnetic field. This coil includes a winding made up of thousands of turns of small superconductive wire, with the winding having a modular geometry including a plurality of axially spaced wire modules. The coil further includes an insulative substance, having a greater coefficient of thermal contraction than that of the wire, distributed in the winding. As the temperature of the coil is reduced from room temperature to its cryogenic operating temperature, the development of localized stress concentrations of sufficient magnitude to rupture the wire, are avoided.

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.

Abstract: According to the present invention, improved cryogenic magnet systems for use in MRI devices are provided. These systems comprise an electromagnet immersed in a first tank containing a first liquefied gas. The first tank is located in an evacuated container that is evacuated to a high vacuum. A refrigerating system external to said evacuated container includes a second gas and a means for liquefying said second gas. A heat radiation shield means surrounding said first tank is cooled by the liquified second gas. Features of the invention include a thermal siphon for cooling the heat radiation shield and neon as the second gas.

Abstract: A rail gun barrel includes a pair of insulators which are axially prestressed in compression.

Abstract: A rail gun barrel includes gas containment means for limiting the penetration of high pressure gas into interfaces between rails and insulating members. The preferred gas containment means comprises one or more channels formed in one or more of the interfaces. In one embodiment of the invention, the channels simply provide space for expansion of gas. In another embodiment, the channels are partially or totally filled with seal material which prevents gas from escaping radially outward beyond the channels.

Abstract: A source of coherent radiation. The source includes an evacuated drift tube having an input end for receiving a beam of relativistic electrons and an output end for providing coherent radiation. A relativistic electron supply provides the beam of electrons to the drift tube input end, and a magnetic field is provided for causing the relativistic electrons to spiral. An azimuthal wiggler causes the spiraling electrons to undergo accelerations while an axial magnetic field is provided for controlling the gyroradii of the spiraling electrons acted upon by the wiggler.

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.

Abstract: Water is decomposed to molecular hydrogen and molecular oxygen in a thermochemical cycle which comprises (i) reacting Cl.sub.2, Br.sub.2 or BrCl with water to obtain oxygen and hydrogen halide; (ii) forming a graphite intercalation compound with a hydrogen halide from step (i) and a metal halide selected from MBr.sub.i Cl.sub.3-i, wherein M is aluminum, gallium or indium and i is 0, 1, 2 or 3, and thereby obtaining hydrogen; (iii) decomposing by heating the graphite intercalation compound formed in step (ii); (iv) recycling the halogen produced in step (iii) for use in step (i); and (v) recycling the metal halide and graphite produced in step (iv) for use in step (ii).