Abstract: A multiple spot x-ray generator is provided that includes a plurality of electron generators. Each electron generator includes an emitter element to emit an electron beam, a meshed grid adjacent each emitter element to enhance an electric field at a surface of the emitter element, and a focusing element positioned to receive the electron beam from each of the emitter elements and focus the electron beam to form a focal spot on a shielded target anode, the shielded target anode structure producing an array of x-ray focal spots when impinged by electron beams generated by the plurality of electron generators. The plurality of electron generators are arranged to form an electron generator matrix that includes activation connections electrically connected to the plurality of electron generators, wherein each electron generator is connected to a pair of the activation connections to receive an electric potential therefrom.

Abstract: An integrated, multi-sensor, Level 1 screening device is described, which system provides a next-generation Explosives Detection System (EDS) that enables high throughput, while drastically reducing false alarms. In exemplary embodiments, the present system comprises a non-rotational, Computed Tomography (CT) system and a non-translational, X-ray diffraction (XRD) system, both in an inline configuration.

Abstract: A field emitter electron gun includes at least one field emitter cathode deposited on a substrate layer and configured to generate an electron beam. An extraction plate having an opening therethrough is positioned adjacent to the at least one field emitter cathode and is operated at a voltage so as to extract the electron beam out therefrom. A meshed grid is disposed between each of the at least one field emitter cathodes and the extraction plate. The meshed grid is configured to operate at a voltage so as to enhance an electric field at a surface of the at least one field emitter cathode. The meshed grid is a one-dimensional grid configured to focus the electron beam received from the at least one field emitter cathode into a desired spot size.

Abstract: A system and method are proposed for cooling the anode of an X-ray tube. A bearing shaft associated with the anode has an associated single rotating seal there around, and contains a liquid metal. A primary liquid metal flow path is used to transfer heat from the anode, and a secondary liquid metal flow path is provided to seal the single rotating seal. Accordingly, the present invention provides an effective means for containing liquid metal in the bearing shaft of an anode assembly, and using the liquid metal to cool the anode of the X-ray tube.

Abstract: This invention relates to demountable conduction cooled current leads for refrigerated superconducting magnets. Such structures of this type generally either allow the warm section of the current lead to be thermally demounted from the magnet after the magnet is powered or both the cold and warm sections of the current leads to be thermally demounted from the magnet after the magnet is powered. In this manner, the heat load placed upon the cryocooler is signficantly reduced when the magnet is powered.

Abstract: This invention relates to refrigerated superconducting MR magnets having integrated cryogenic gradient coils. In particular, the amount of eddy currents produced by the magnet are substantially reduced while reducing the size and weight, and, therefore, the cost of the superconducting magnet required to produce an acceptable MR image.

Abstract: This invention relates to an apparatus and method for measuring the resistance of superconductors. Structures of this type, generally, allow the resistance of the superconductor to be accurately measured in a non-destructive manner by using a bifilar coil which includes an integrated loop/switch formed from the bifilar coil.

Abstract: This invention relates to refrigerated superconducting eddy current free MR magnets having integrated gradient coils. In particular, the amount of resultant eddy currents produced by the magnet are substantially reduced while reducing the size and weight, and, therefore, the cost of the superconducting magnet required to produce an acceptable MR image.

Abstract: The invention relates to refrigerated superconducting MR magnets having integrated gradient coils. In particular, the amount of eddy currents produced by the magnet are substantially reduced while reducing the size and weight, and, therefore, the cost of the superconducting magnet required to produce an MR image.

Abstract: Four magnet cartridge axial supports are provided to prevent axial motion between the magnet cartridge and the surrounding vacuum vessel. Each axial support includes two high strength steel rods in parallel. The rods are brazed to a bar on one end which mounts to the magnet cartridge. The other end of the rods is brazed to a threaded stud which is secured by a bolt to a bracket secured to the vacuum vessel.

Abstract: A method of passively shimming a magnet having a central bore using ferromagnetic shims is provided. The field strength in the bore of the magnet is measured at a predetermined number of points. The field inhomogeneity is determined from the measured field strengths. The fields created by a single shim of known size when positioned, at different predetermined positions in the bore of the magnet is determined. The shim locations in the bore of the magnet and shim size are determined using a linear programming solver to minimize the field inhomogeneity and the total amount of shims used. The shim sizes are determined based on the measured field in the bore of the magnet and the field created by a single shim when positioned at a predetermined number of locations. The shim size at the appropriate locations are adjusted to the determined values and the field strength of the magnet is again measured at the predetermined points.

Abstract: A refrigerated superconductive magnet is provided with six magnet cartridge radial struts supporting the magnet cartridge in the vertical and lateral directions. The struts are positioned such that two lateral struts on each end of the magnet cartridge react against the contact force of the cryocooler cold head and support half of the vertical (gravitational) load of the magnet cartridge. Two vertical struts support the other half of the vertical load. The vertical struts pivot to allow the cartridge axial centerline to shrink towards the cryocooler interface during cool down. The strut attachment points have been located near the horizontal midplane in order to minimize the sag of the magnet cartridge due to its own weight.

Abstract: Two pair of thermal shield axial supports are provided. Each support includes a strand of wire brazed on either end into threaded studs. One stud is threaded into a topped hole in the end of the magnet cartridge. The stud on the other end extends through a clearance hole on the end flange of the thermal shield. Belleville spring washers are compressed against the shield by a nut. Prior to cool down, the Belleville washers are compressed. As the shield and magnet cool down, the shield contracts axially with respect to the magnet cartridge, thus relaxing the washer stack compression. The wire tension relaxes from the maximum pretension to a nominal tension at operating temperature.

Abstract: A low thermal conductance support for a radiation shield in a magnetic resonance magnet is provided. Spacer means are situated partially in apertures in a cylindrical coil form having superconducting windings supported from a vacuum vessel. The spacer means are spaced away from the aperture walls and are secured at one end to the coil form. The spacer means protrude radially beyond the coil form surface and contact a radiation shield. The length of the spacer means is greater than the distance between the surface of the coil form and shield thereby increasing the thermal conduction path length between form and shield.

Abstract: A magnetic resonance magnet is provided having a cylindrical vacuum vessel and a cylindrical cartridge having superconductor windings, situated inside the vacuum vessel. The cartridge defines a pair of circumferential grooves in the outer surface of the cartridge near each end of the cartridge. Means are affixed to the vacuum housing for securing the ends of four cables to the housing. The securing means are situated in pairs circumferentially spaced on either side of where a first diametral line passing through said grooves on one end of the cartridge emerges radially on either side of the housing. The securing means are also situated in pairs circumferentially spaced on either side of where a second imaginary diametral line passing through said grooves on other end of the cartridge emerges radially on either side of the housing.

Abstract: A thermally efficient electrically insulating joint operable at liquid nitrogen temperatures and below is provided for connecting a current lead to a cryocooler heat station. The joint includes clamping means, two indium sheets and a ceramic spacer. The ceramic spacer material can be either beryllia or alumina. The spacer has two faces situated opposite one another. Each of the indium sheets contacts a respective one of the faces. The ceramic spacer with the indium sheets on either side is situated between the current lead and the cryocooler heat station. The clamp means urge the cryocooler heat station and the lead together with sufficient force to cause the indium layers to conform to the surface with which they are in contact.

Abstract: A shim set for passively shimming (3,2) and (3,-2) harmonic terms in the field of the magnetic resonance magnet having a cylindrical bore, is provided. Four shims of ferromagnetic material, all of the same size, are secured to the interior of the bore of the magnet. The length of each of the shims is greater than its width. The first two of the shims are secured diametrically opposite one another, near one end of the magnet, with the length of the shims extending circumferentially. One of the first two shims is situated so that a polar angle is created between the axial centerline of the cylindrical bore and an imaginary line extending through the center of the cylindrical bore and the center of the shim, at about 30.degree.-44.degree. with 38.degree. being the most desirable location. The second two of the four shims are positioned symmetrically about the axial midplane of the cylindrical bore from the first two of the four shims and rotated 90.degree. circumferentially relative to the first two shims.

Abstract: A method of predicting the locations and strengths of passive shims in the bore of a magnetic resonance magnet, necessary to attain imaging quality homogeneity in the bore of the magnet is provided. Electromagnetic coils are not needed to provide any shimming. The magnetic field effect of an arc of magnetized steel as a function of its position in the magnetized bore is determined. The locations at which an arc provides the most beneficial shimming effect are next determined. The most promising locations are used as a starting point for an iterative routine which attempts to identify a group of shim locations which will provide a prediction of inhomogeneity within the specified limit. The shims are placed in the magnet bore, the field measured and the result compared to prediction. If improvement is predicted by another iteration with the shim locations fixed, the determined thickness changes are implemented.

Abstract: A passive shimming assembly is provided which allows flexible positioning of a plurality of arcuate segments of steel in the bore of a magnet, with enough degrees of freedom to adequately shim a magnetic resonance magnet to a level of inhomogeneity required for imaging without the use of correction coils.

Abstract: An NMR magnet correction coil comprises a plurality of cylindrical coil forms coaxially disposed with radially exterior coil forms possessing saddle coils so as to provide slits in the exterior forms. The outermost coil form is wrapped with a non-magnetic wire in order to keep the forms in a fixed relationship. If three or more coil forms are employed, the inner forms are wrapped with a band of material which also serves to provide a spiral flowpath for cryogens such as liquid helium. A pair of keys is provided for tieoff and insulation of the outer wire band, as well as for positioning of the entire assembly.