Abstract: A magnetic resonance coil system 18 allows for the use of modular components and which in one embodiment is particularly well-suited for use with small animals and includes an animal receiving apparatus 202, a transmit coil module 204, and a receive coil module 206. The receive coil module 206 includes a cryogenic receive coil. The coil system 18 is selectively insertable in the bore of the gradient coil of a magnetic resonance examination system.

Abstract: A magnetic resonance coil system 18 allows for the use of modular components and which in one embodiment is particularly well-suited for use with small animals and includes an animal receiving apparatus 202, a transmit coil module 204, and a receive coil module 206. The receive coil module 206 includes a cryogenic receive coil. The coil system 18 is selectively insertable in the bore of the gradient coil of a magnetic resonance examination system.

Abstract: A magnetic resonance coil system 18 allows for the use of modular components and which in one embodiment is particularly well-suited for use with small animals and includes an animal receiving apparatus 202, a transmit coil module 204, and a receive coil module 206. The receive coil module 206 includes a cryogenic receive coil. The coil system 18 is selectively insertable in the bore of the gradient coil of a magnetic resonance examination system.

Abstract: A piston assembly for use in a motor comprises a cylinder having a bore, an electrically conductive piston reciprocally disposed within the cylinder bore, a gas cavity formed within the piston, and one or more gas bearings associated with the piston, each of the one or more gas bearings including an aperture formed within the piston and an electrically conductive tubular member extending through the aperture, the tubular member having a lumen in communication between the gas cavity and the cylinder bore. The piston assembly may be used in connection with a motor used in a cryocooler that is driven by oscillating magnetic energy fields.

Abstract: A piston assembly for use in a motor comprises a cylinder having a bore, an electrically conductive piston reciprocally disposed within the cylinder bore, a gas cavity formed within the piston, and one or more gas bearings associated with the piston, each of the one or more gas bearings including an aperture formed within the piston and an electrically conductive tubular member extending through the aperture, the tubular member having a lumen in communication between the gas cavity and the cylinder bore. The piston assembly may be used in connection with a motor used in a cryocooler that is driven by oscillating magnetic energy fields.

Abstract: A magnet ring assembly for use with a piston assembly includes a cylindrical magnet holder having an inner surface, an annular ledge formed around the inner surface of the cylindrical magnet holder, and a swaged axial edge opposite the annular ledge, and a plurality of arcuate magnet sectors having a radially uniform magnetic polarity, the plurality of magnets being bonded around the inner surface of the cylindrical magnet holder, each of the plurality of magnets having opposing axial edges, one of the axial edges being disposed on the annular ledge, and the other of the axial edges being captured by the swaged axial edge of the cylindrical magnet holder. The magnet ring assembly can be used in connection with a crycooler.

Abstract: A regenerator material for use inside a displacer of a Stirling cycle cryocooler includes a plurality of circular disks formed from a synthetic felt that is preferably polyester. The plurality of disks have an outer diameter that is greater than the inner diameter of the displacer. The plurality of circular disks form a stack within the displacer. The regenerator material minimizes operational variation between different cryocoolers. In addition, the regenerator material can be easily filled into the cryocooler displacer.

Abstract: A magnet ring assembly for a piston/magnet assembly that can be used in a Stirling cycle cryocooler comprises a cylindrical magnet holder and a plurality of magnet sectors disposed on the inner surface of the magnet holder. The magnet sectors are captured in the rotational direction by bonding the magnet sectors to the inner surface of the magnet holder. The magnet sectors are also captured in the radial direction by providing them with a uniform radial magnetic field, such that they mutually repel each other against the inner surface of the magnet holder. Also, the edges of the magnet sectors are shaped, such any one magnet sector is prevented from being displaced radially inward by the edges of adjacent magnet sector. The magnet sectors are captured in the axial direction by forming an annular ledge on the inner surface of the magnet holder on which one axial edge of each magnet sector rests, and swaging the axial edge of the magnet holder around the other axial edge of each magnet sector.

Abstract: An improved HTSC filter system design. An improved HTSC filter system comprises a cryocooler and dewar assembly, a heat dissipation assembly and at least one heat pipe providing a thermal coupling between said heat dissipation assembly and said cryocooler and dewar assembly. In a preferred embodiment, the cryocooler and dewar assembly is environmentally sealed within a double-walled aluminum canister, and the heat pipes are formed from stainless steel tubes having a predetermined amount of ammonia provided therein.

Abstract: An improved HTSC filter system design. An improved HTSC filter system comprises a cryocooler and dewar assembly, a heat dissipation assembly and at least one heat pipe providing a thermal coupling between said heat dissipation assembly and said cryocooler and dewar assembly. In a preferred embodiment, the cryocooler and dewar assembly is environmentally sealed within a double-walled aluminum canister, and the heat pipes are formed from stainless steel tubes having a predetermined amount of ammonia provided therein.

Abstract: An electrical interconnect provides a path between cryogenic or cryocooled circuitry and ambient temperatures. As a system, a cryocable 10 is combined with a trough-line contact or transition 20. In the preferred embodiment, the cryocable 10 comprises a conductor 11 disposed adjacent an insulator 12 which is in turn disposed adjacent another conductor 13. The components are sized so as to balance heat load through the cryocable 10 with the insertion loss. In the most preferred embodiment, a coaxial cryocable 10 has a center conductor 11 surrounded by a dielectric 12 (e.g. Teflon.TM.) surrounded by an outer conductor 13 which has a thickness between about 6 and 20 microns. The heat load is preferably less than one Watt, and most preferably less than one tenth of a Watt, with an insertion loss less than one decibel. In another aspect of the invention, a trough-line contact or transition 20 is provided in which the center conductor 11 is partially enveloped by dielectric 12 to form a relatively flat portion 28.

Abstract: A Cryogenic Cooling System generally comprises a portable Dewar and a charging station for the Dewar. In the preferred embodiment, a HTSC device, such as a MRI coil, is contained in the Dewar which uses liquid nitrogen as a cryogenic coolant. The Dewar includes a reservoir for holding cryogenic fluid, an optional wicking material, a transfer tube between the reservoir and the HTSC device (or wick), and a vacuum space. Preferably a vent channel is adjacent the reservoir and provides an escape path for evaporating gas from the wick and/or HTSC device. The vent channel preferably provides a feed-back system: as more cryogenic coolant is transferred via the transfer tube, more cool gas is vented through the channel which cools the reservoir and thereby reduces the transfer. A charging system may also be provided as a source of cryogenic coolant. In the preferred embodiment, the charging system comprises a relatively large reservoir for liquid nitrogen.

Abstract: An infrared dewar-detector assembly for use as a common module which is interchangeable between various military infrared detection systems. The detector is cooled to cryogenic temperature for improved sensitivity. The dewar of the common module incorporates a metal coldfinger mounted on a base plate for attachment to an associated cryo-engine. The coldfinger supports the detector on a beryllium bridge platform. The configurations of both the platform mount and the base plate are selected to minimize the vibrations transmitted to the detector.Signal paths from the detector include ribbon cables extending within the vacuum side of the dewar and having indium dot terminations making direct connections with a ceramic feedthrough header which, on the ambient pressure side of the unit, also includes indium pocket contacts for direct connection to the plug terminals of the unit.

Abstract: A dual Joule-Thompson cryostat assembly (10) is provided which includes first and second concentrically aligned cryostats (100) and (102), respectively, which are disposed in the coldwell of a detector assembly (12). Each of the cryostats is connected to a source of pressurized gas which is discharged into the coldwell. The pressurized gas is directed at the components to be cooled such that the relatively high discharge velocity produces a relatively high film coefficient for maximizing heat transfer. Both the inner and outer cryostats, (100) and (102), respectively, of the dual cryostat assembly (10) are designed to direct pressurized gas at an electromagnetic detector (26). In addition, the inner cryostat (100) directs pressurized gas toward the outer cryostat (102) for precooling the outer cryostat (102). Furthermore, the outer cryostat (102) is designed to direct pressurized gas for cooling a coldshield (50) surrounding the detector (26).

Abstract: An infrared detector assembly (12) of the type used in munitions and night vision systems having an improved focal plane platform (10) construction. In accordance with this invention, the thermally conductive focal plane platform (10) supports a detector array (26) and integrated readout chips (28). The focal plane platform (10) includes relatively thermally non-conductive inserts (38) disposed in cavities (36) positioned generally below each integrated read out chip (28). The inserts insulate the chips (28) during cryogenic cooling of detector array (26). Freeze-out of the chips (28) is thereby inhibited.

Abstract: An infrared detector assembly (10) of the type used in munitions and night vision systems having improved coldfinger dewar tube (22). Such detectors include a tubular coldfinger which is surrounded by a vacuum and has a cold end (24) which supports the infrared detector array (30) and related components, and an opposite warm end (26). In accordance with this invention, the coldfinger tube is a two-material composite structure having plastic (44) and metal (42) layers. The plastic layer provides the necessary bending stiffness to support the cold end components while minimizing heat transfer rate between the warm and cold ends of the tube. The metal film layer provides a gas seal to preserve the integrity of the dewar vacuum, but is sufficiently thin to provide a minimal increase in thermal conductivity. The compositie coldfinger tube in accordance with this invention features lower overall heat conductivity thus minimizing cryogenic cooling requirements while providing the necessary bending stiffness.

Abstract: Demand flow cryostat 10 has an expansion nozzle 24 from which flow is controlled by valve needle 32. Bellows 34 regulates flow to maintain substantially constant temperature in the cooled space adjacent interior surface 26. Guide tube 38 and felt 44 control flow of the mixed liquid-vapor cryogen to stabilize temperature at the electronic device 30 which is cooled by the cryostat.