High Speed Spin Testing of Reinforced 2212 Coils for High Field NMR Magnets.

Bi-2212 superconductors have very good performance in field, and recent developments by Solid Materials Solutions (SMS) of Chelmsford, MA to mechanically reinforce this material will help realize the potential of this material for these highfield (> 1 GHz-class) NMR magnets. While the strength of these materials can be tested using a conventional tensile test, it is difficult-to-impossible to test coils in the high-field environment required to impose the large Lorentz stresses on the superconductor, as the available warm bore for high-field magnets is usually too small to test typical NMR insert coils, which typically have either a 60 or 80-mm winding diameter. Since it is important to test the coils-and not just wire-in the high-stress environment, as such factors as differential thermal contraction (between mandrel, wire, insulation and epoxy) and stress-concentrations (due to layer-to-layer crossover, for example) only can be tested in coil form, the objective of this study is to simulate the high-field magnet environment by spinning these coils at very high speed (up to 100,000 rpm) using the spin test facilities of Barbour-Stockwell (BSI) in Woburn, MA.

Progress in High-Speed Spin Testing of Superconducting Wire and Tapes for High-Field NMR Magnet Qualification.

This paper summarizes the status of a 3-year, NIH-funded research project to study the strength of high temperature superconductors under high circumferential hoop stress, in order to qualify these materials for high-field (> 1 GHz-class NMR magnets. The unique approach presented here is to spin test coils at high rotational speeds, approaching 100,000 rpm, in order to induce the necessary hoop stress. Thermal strain compatibility between the Bi-2212 wire and Inconel wire has been qualified, including thermal cycling.

A Tabletop Persistent-Mode, Liquid Helium-Free 1.5-T MgB2 "Finger" MRI Magnet: Construction and Operation of a Prototype Magnet.

This paper presents results of construction and operation of a persistent-mode, liquid-helium-free, small-scale prototype magnet for the development of a tabletop 1.5-T "finger" MRI system for osteoporosis screening. The prototype magnet, composed of 2 MgB coils, one superconducting joint, and a persistent-current switch (PCS) built from a portion of one coil, was wound with a one continuous ~80-m long unreacted and monofilament MgB wire and then reacted.

A REBCO Persistent-Current Switch, Immersed in Solid Nitrogen, Operating at Temperatures near 10 K.

We present design and test results for a thermally-activated persistent-current switch (PCS) applied to a double pancake (DP) coil (151 mm ID, 172 mm OD), wound, using the no-insulation (NI) technique, from a 120-m long, 76-μm thick, 6-mm wide REBCO tape. For the experiments reported in this paper, the NI DP assembly was immersed in a volume of solid nitrogen (SN2), cooled to a base temperature of 10 K by conduction to a two-stage cryocooler, and energized at up to 630 A. The DP assembly operated in quasi-persistent mode, with the conductor tails soldered together to form a close-out joint with resistance below 6 nΩ.

A persistent-mode 0.5 T solid-nitrogen-cooled MgB2 magnet for MRI.

This paper presents construction details and test results of a persistent-mode 0.5-T MgB magnet developed at the Francis Bitter Magnet Lab, MIT. The magnet, of 276-mm inner diameter and 290-mm outer diameter, consisted of a stack of 8 solenoidal coils with a total height of 460 mm.

A REBCO Persistent-Current Switch (PCS): Test Results and Switch Heater Performance.

In this paper, we report preliminary results of our on-going effort to develop a superconducting persistent-current switch (PCS) for REBCO pancake coils that will be operated in liquid helium. In the first part of this paper, we briefly describe experimental results of our PCS operated in the temperature range 77-57 K, i.e.

Persistent-current switch for pancake coils of rare earth-barium-copper-oxide high-temperature superconductor: Design and test results of a double-pancake coil operated in liquid nitrogen (77-65 K) and in solid nitrogen (60-57 K).

We present design and test results of a superconducting persistent current switch (PCS) for pancake coils of rare-earth-barium-copper-oxide, REBCO, high-temperature superconductor (HTS). Here, a REBCO double-pancake (DP) coil, 152-mm ID, 168-mm OD, 12-mm high, was wound with a no-insulation technique. We converted a ∼10-cm long section in the outermost layer of each pancake to a PCS.

High-Resolution Magnetic Field Mapping System With an NMR Probe.

This paper presents a high-resolution magnetic field mapping system in development that is capable of collecting spatial magnetic field data for NMR magnets. An NMR probe was designed and built with a resonant frequency of 5.73 MHz.

A Theoretical Design Approach for Passive Shimming of a Magic-Angle-Spinning NMR Magnet.

This paper presents a passive shimming design approach for a magic-angle-spinning (MAS) NMR magnet. In order to achieve a 1.5-T magic-angle field in NMR samples, we created two independent orthogonal magnetic vector fields by two separate coils: the dipole and solenoid.

An Analytical Approach towards Passive Ferromagnetic Shimming Design for a High-Resolution NMR Magnet.

This paper presents a warm bore ferromagnetic shimming design for a high resolution NMR magnet based on spherical harmonic coefficient reduction techniques. The passive ferromagnetic shimming along with the active shimming is a critically important step to improve magnetic field homogeneity for an NMR Magnet. Here, the technique is applied to an NMR magnet already designed and built at the MIT's Francis Bitter Magnet Lab.

A High-Resolution 1.3-GHz/54-mm LTS/HTS NMR Magnet.

A high-resolution 1.3-GHz/54-mm low-temperature superconducting/high-temperature superconducting (HTS) nuclear magnetic resonance magnet (1.3 G) is currently in the final stage at the Massachusetts Institute of Technology Francis Bitter Magnet Laboratory.

Operation of a 130-MHz/9-mm Compact HTS Annulus Magnet With a Micro-NMR Probe.

In this paper, we report final operation results of our compact annulus NMR magnet, named YP2800, with a homemade micro-NMR probe in a bath of liquid helium at 4.2 K. YP2800 comprises of a stack of 2800 YBCO "plate annuli," 0.

Strain in YBCO Double-Pancake Coil With Stainless Steel Overband Under External Magnetic Field.

This paper deals with the mechanical strain issue in a high-temperature superconducting (HTS) insert for a GHz-class (> 23.5 T) LTS/HTS NMR magnet. We present results, experimental and analytical, of hoop strains in a double-pancake (DP) test coil, wound with 6-mm wide YBCO coated conductor (CC) and equipped with strain gauges at their innermost and outermost turns.

A 1.5-T Magic-Angle Spinning NMR Magnet: 4.2-K Performance and Field Mapping Test Results.

We present results of full-current testing at 4.2 K of a -axis 0.866-T solenoid and an -axis 1.

Construction and Persistent-Mode Operation of MgB Coils in the Range 10-15 K for a 0.5-T/240-mm Cold Bore MRI Magnet.

This paper presents construction and persistent-mode operation results of MgB coils for a 0.5-T/240-mm cold bore MRI magnet, wind-and-react with monofilament MgB wire at the MIT Francis Bitter Magnet Laboratory. The magnet, of respective inner and outer diameters of 276 and 290 mm and a total height of 460 mm, has center field of 0.

Development of a 0.5-T/240-mm MgB MRI Magnet: Assembly Design and Module Coils.

This paper presents the latest results from our continued development of a 0.5-T/240-mm MgB MRI magnet at the MIT Francis Bitter Magnet Laboratory. Because we have successfully developed our superconducting joint technique with a monofilament MgB wire, manufactured by Hyper Tech Research, Inc.

Temporal Enhancement of Trapped Field in a Compact NMR Magnet Comprising YBCO Annuli.

Temporal "enhancement" of trapped fields was observed in the central region of a compact NMR magnet comprising a stack of 2800 YBCO "square" annuli (YP2800), field-cooled at 4.2 K. This paper presents an analytical model to simulate the trapped field enhancement in YP2800.

A 1.5-T/75-mm Magic-Angle-Spinning NMR Magnet.

We are currently working on a program to complete a 1.5-T/75-mm RT (room temperature) bore MAS (magic-angle-spinning) NMR (nuclear magnetic resonance) magnet. The MAS magnet comprises a z-axis 0.

No-insulation multi-width winding technique for high temperature superconducting magnet.

We present a ) winding technique for an HTS (high temperature superconductor) magnet consisting of double-pancake (DP) coils. The NI enables an HTS magnet self-protecting and the MW minimizes the detrimental anisotropy in current-carrying capacity of HTS tape by assigning tapes of multiple widths to DP coils within a stack, widest tape to the top and bottom sections and the narrowest in the midplane section. This paper presents fabrication and test results of an NI-MW HTS magnet and demonstrates the unique features of the NI-MW technique: self-protecting and enhanced field performance, unattainable with the conventional technique.

Magic-Angle-Spinning NMR Magnet Development: Field Analysis and Prototypes.

We are currently working on a program to complete a 1.5 T/75 mm RT bore magic-angle-spinning nuclear magnetic resonance magnet. The magic-angle-spinning magnet comprises a -axis 0.

Persistent-mode high-temperature superconductor shim coils: A design concept and experimental results of a prototype 1 high-temperature superconductor shim.

Design, fabrication, and test results of a type persistent-mode high-temperature superconductor (HTS) shim coil are presented. A prototype 1 rectangle-loop shim, cut from 46-mm wide Y-Ba-Cu-O tape manufactured by AMSC, was fabricated and tested at 77 K. The HTS shim, much thinner than the conventional NbTi shim, is placed inside the main magnet and immune to its diamagnetic wall effects.

No-Insulation Coil Under Time-Varying Condition: Magnetic Coupling With External Coil.

This paper presents experimental and analytical studies on the time-varying behavior of an NI (no-insulation) high-temperature superconductor pancake coil, alone or magnetically coupled to an external coil. An NI coil and another insulated coil (as an external), both of identical winding i.d.

Monofilament MgB Wire for a Whole-Body MRI Magnet: Superconducting Joints and Test Coils.

This paper presents recent results from our continued development of a 0.5 T whole-body MRI magnet at the Francis Bitter Magnet Laboratory. HyperTech Research Corp.

YBCO and Bi2223 Coils for High Field LTS/HTS NMR Magnets: HTS-HTS Joint Resistivity.

This paper presents our latest experimental results on high-temperature superconducting (HTS) splice joints for HTS insert coils made of YBCO and Bi2223, that comprise a 1.3 GHz low-temperature superconducting/HTS nuclear magnetic resonance magnet currently under development at Francis Bitter Magnet Laboratory. HTS splice joint resistivity at 77 K in these insert coils must be reproducible and 100 nΩ cm.

Bulk and Plate Annulus Stacks for Compact NMR Magnets: Trapped Field Characteristics and Active Shimming Performance.

We have constructed two "annulus" magnets, YP2800 and YB10; each consists of 2800 YBCO thin square "plate annuli" (YP2800) and 10 YBCO thick "bulk annuli" (YB10). Their trapped field characteristics, spatial and temporal, were investigated and compared, experimentally and analytically. Two sets of field-cooling tests were performed at 77 K: (1) maximum trapped field tests, where a 2-T background field was applied to investigate the maximum trapped field capability of the two magnets; and (2) reduced trapped field tests, where spatial homogeneity improvement of the two magnets was investigated after field cooling with a reduced background field.