Abstract: A cylindrical NMR sample cell is made from a first plastic material having Young's modulus Y.sub.1, tensile strength S.sub.1, and density p.sub.1 with precision outside diameter (OD) d.sub.4, wherein the outside diameter fits inside a ceramic NMR MAS rotor having modulus Y.sub.3 and density p.sub.3. The sample cell comprising a sample chamber with a concentric cylindrical opening at one end having inside diameter d.sub.2. A cylindrical plug is made from a second plastic material having modulus Y.sub.2, strength S.sub.2, and density p.sub.2 with plug outside diameter d.sub.1 to fit firmly inside the mouth of the cell, so as to seal the sample of density p.sub.4 inside the cell with inside cell diameter d.sub.3 when stationary and to seal when spinning at a high rate of speed inside the ceramic rotor. More-over, the following materials properties and relationships are satisfied: Y.sub.1> 0.8 GPa, Y.sub.1 <4 GPa, Y.sub.2 <3.4 GPa, S.sub.1 >8 MPa, S.sub.2 >3 MPa, p.sub.2 >880 kg/m.sup.3, p.sub.

Abstract: A single-tuned rf-gradient saddle coil is used for an internal NMR lock in a high-field NMR probe. The non-dipolar lock coil geometry is chosen such that its filling factor and Q are maximized subject to the constraint that its coupling coefficient to two orthogonal saddle coils is zero. Various quadrupolar and octopolar rf coils are disclosed for use in NMR probes having three or four sample coils for multi-nuclear triple resonance or homonuclear decoupling.

Abstract: A high-conductivity ceramic coil form with an internal water jacket is used to simplify water cooling for 3-axis MRI gradient coil configurations on a single cylindrical coilform. Crescent-shaped, axially aligned coils are symmetrically employed on either side of the axial symmetry plane to increase transversely the region of field linearity. These crescent coils may be used in conjunction with Golay-type coils for improved switching efficiency. Lead-filled copper tubing may be used to reduce acoustic noise from pulsed coils in high external magnetic fields.

Abstract: A high-conductivity ceramic coil form with an internal water jacket is used to simplify water cooling for 3-axis MRI gradient coil configurations on a single cylindrical coilform. Crescent-shaped, axially aligned coils are symmetrically employed on either side of the axial symmetry plane to increase transversely the region of field linearity. These crescent coils may be used in conjunction with Golay-type coils for improved switching efficiency. Lead-filled copper tubing may be used to reduce acoustic noise from pulsed coils in high external magnetic fields.

Abstract: A structure provides a gradient field useful in magnetic resonance imaging. Axially aligned, solenoidal-like coils are symmetrically distributed around the perimeter of the bore of a superconducting magnet in an MRI system so as to produce transverse gradients in the X and Y directions with exceptionally high efficiency and exceptionally low acoustic noise. Opposed solenoidal endcoils may be added to reduce axial flux leakage by generating an axial quadrupolar field. Radially aligned coils may be positioned near each end of the axial coils to reduce leakage flux by adding a transverse quadrupolar field to form a resulting octopolar field. Typically, the solenoid-like coils have a mean radius of about 15% of the radius of that of the imaging ellipsoidal region. A thick-walled stainless steel, copper and resin cylinder may be used to simplify gradient shielding problems. Silver plated bronze or stainless steel sheet is used as an rf shield.

Abstract: Whirl forces in a high-speed hydrostatic air bearing are reduced by orienting the gas supply nozzles so that the pressurized gas enters the bearing opposite to the direction of rotation of the shaft. Stiffness also is thereby increased. Stable operation at supersonic surface speeds may thus be achieved. Diffuser chamfers may be added to the bearing surface to enhance performance at very high pressure ratios. This anti-whirl air bearing is effectively used to support a nuclear magnetic resonance cylindrical sample container capable of high-speed spinning for line-narrowing of solid samples. Motive power required to spin the container at supersonic surface speeds is provided by radial-inflow microturbines with tip diameter less than the bearing diameter and supersonic inlet gas velocities. An axial thrust bearing is included between the microturbine and the sample container.

Abstract: A single NMR sample coil of inductance L.sub.S, in series with a mid-frequency (MF) tuning inductor grounded at one end, is doubly broadbanded using a first high-voltage broadband capacitor matching network in series with the two coils for the LF tuning and a second high-voltage broadband capacitor matching network connected to the junction between the two coils for the MF tuning. Isolation between the MF and LF ports is achieved by proper choice of a plug-in isolation capacitor between the two broadband matching networks. An inductively coupled floating HF tank circuit is inserted in series with one of the leads from the sample coil to produce the triple resonance circuit. The tuning elements for this HF tank are mounted on top of the adjacent broadband matching network. A second floating HF tank circuit may be inserted in series with the other lead from the sample coil to produce a balanced-HF triple resonance circuit or an unbalanced quad-resonance circuit.

Abstract: A high-strength, thin-wall ceramic cylinder partially closed at one end, with radial-inflow turbine blades ground into the partially closed end thereof, provides the rotational drive, surface protection, and burst strength necessary to contain and spin a low strength, disposable soft ceramic capsule, loaded with a sample for NMR experiments, at high rotational speeds inside an NMR receiver/transmitter coil. An improved radial inflow turbine design results in higher efficiency for micro-turbines. A cylindrical air journal bearing at both ends provides radial stability and support. An axial thrust air bearing is formed at the end opposite the turbine blades between the sacrificial bottom of the soft capsule and a thrust ring. The high-strength ceramic is typically of a partially stabilized zirconia or hot pressed silicon nitride. The disposable capsule is typically of hexagonal boron nitride.

Abstract: An NMR DOR sample spinner includes an inner-rotor that is driven by a radial-inflow microturbine at each end, supported radially by anti-whirl air bearings, and supported axially by thrust bearings at each end thereof. The DOR spinner further comprises an outer-rotor that houses the inner-rotor bearing and drive nozzles such that the inner-rotor axis is inclined with respect to the axis of the outer-rotor at an angle of typically 30.56.degree.. The outer-rotor is driven by a radial-inflow microturbine at each end, supported radially on anti-whirl air bearings, and supported axially by thrust bearings at each end thereof. The outer-rotor further comprises ceramic bearing races at each end that hold the sample drive nozzles in place. The outer microturbines are screwed to the outer-rotor and hold the bearing races in place. Drive and bearing gas for the inner-rotor is supplied through slip-fit, precision axial tubes at each end of the outer-rotor.

Abstract: The frictional heating of an NMR sample spinner supported on a cylindrical gas bearing inside a cylindrical bearing stator is negated by recirculating the turbine exhaust gas over the rotor surface inside the RF coil. The technique is more effective with microturbines of relatively high insentropic efficiency. Plugs extend axially into the sample container from each end so that the sample is confined to the central region beyond the gas bearing region so the thermal gradients are minimized and RF homogeneity is improved.

Abstract: The MTS radiator consists of planar arrays of micro-tube strip modules, each of which contain two or three rows of about 200 properly spaced microtubes per row. The three-dimensional tubular titanium structure with support members between microtubes maximizes stiffness and strength per mass. The working fluid--typically hydrogen at 0.1 to 1 MPa--circulates through the microtubes, and most of the radiation occurs from their walls, which are only 0.2 to 0.4 mm thick. This allows specific mass below 1 kg/m.sup.2. The operating temperature range is typically 200-650 K. The radiator's radiating surface comprises a heavily oxidized, metal alloy with a corrosion resistant, refractory alloy film deposited on it.

Abstract: A high-strength, thin-wall ceramic cylinder partially closed at one end, with radial-inflow turbine blades ground into the partially closed end thereof, provides the rotational drive, surface protection, and burst strength necessary to contain and spin a low strength, disposable soft ceramic capsule, loaded with a sample for NMR experiments, at high rotational speeds inside an NMR receiver/transmitter coil. An improved radial inflow turbine design results in higher efficiency for micro-turbines. A cylindrical air journal bearing at both ends provides radial stability and support. An axial thrust air bearing is formed at the end opposite the turbine blades between the sacrificial bottom of the soft capsule and a thrust ring. The high-strength ceramic is typically of a partially stabilized zirconia or hot pressed silicon nitride. The disposable capsule is typically of hexagonal boron nitride.

Abstract: A double-tuned NMR sample excitation coil has a first end connected through a first balancing inductor to ground and a second end connected through a second balancing inductor to a low-frequency (LF) capacitor tuning and matching network. Two two balancing inductors have inductance less than 50% but greater than 10% that of the excitation coil. Each balancing coil is tuned by a capacitor network to an independent resonant frequency when disconnected from the sample coil that is less than 95% but greater than 60% of the final high frequency (HF) resonance. Moreover, both such independent resonant frequencies are equal within 10%. Broadband operation is possible under a variety of temperatures and the circuit works with high-speed sample spinners.

Abstract: A new approach to the theory of heat exchanger optimization is presented which shows the advantages of using low Reynolds and Nusselt numbers and low flow velocities along with a novel design, the microtube-strip (MTS) counterflow heat exchanger. The MTS exchanger in the preferred embodiment consists of a number of small modules connected in parallel. Each module typically contains eight rows of one hundred tubes, each of 0.8 mm outside diameter and 0.16 m length. The tubes are metallurgically bonded via the diffusion welding technique to rectangular header tube strips at each end. Caps suitable for manifolding are welded over the ends. Cages are provided to cause the shell-side fluid to flow in counterflow fashion over substantially all of the tube length, and suitable manifolds are provided to connect the modules in parallel. This design results in the highest power densities of any known design for single phase exchangers.

Abstract: A capacitively shortened coaxial resonator for making nuclear magnetic resonance measurements includes inner and outer concentrically arranged metal cylinders. The cylinders define therebetween a sample region and are shorted electrically by a conductive cap which closes one end of the inner and outer cylinders. A capacitor is connected across the cylinders at the opposite open end and functions to resonate with the inductance of a coaxial conductor formed by the short circuited cylinders. Samples placed in the sample region are mounted on an air bearing and rotated by means of air holes formed in the inner and outer cylinders.

Abstract: A new approach to the theory of heat exchanger optimization is presented which shows the advantages of using low Reynolds and Nusselt numbers and low flow velocities along with a novel design, the microtube-strip (MTS) counterflow heat exchanger. The MTS exchanger in the preferred embodiment consists of a number of small modules connected in parallel. Each module typically contains eight rows of one hundred tubes, each of 0.8 mm outside diameter and 0.16 m length. The tubes are metallurgically bonded via the diffusion welding technique to rectangular header tube strips at each end. Caps suitable for manifolding are welded over the ends. Cages are provided to cause the shell-side fluid to flow in counterflow fashion over substantially all of the tube length, and suitable manifolds are provided to connect the modules in parallel. This design results in the highest power densities of any known design for single phase exchangers.