A Feasibility Study of High-Strength Bi-2223 Conductor for High-Field Solenoids.

We performed a feasibility study on a high-strength Bi2-x Pb x Sr2Ca2Cu3O10-x (Bi-2223) tape conductor for high-field solenoid applications. The investigated conductor, DI-BSCCO Type HT-XX, is a pre-production version of Type HT-NX, which has recently become available from Sumitomo Electric Industries (SEI). It is based on their DI-BSCCO Type H tape, but laminated with a high-strength Ni-alloy. We used stress-strain characterizations, single- and double-bend tests, easy- and hard-way bent coil-turns at various radii, straight and helical samples in up to 31.2 T background field, and small 20-turn coils in up to 17 T background field to systematically determine the electro-mechanical limits in magnet-relevant conditions. In longitudinal tensile tests at 77 K, we found critical stress- and strain-levels of 516 MPa and 0.57%, respectively. In three decidedly different experiments we detected an amplification of the allowable strain with a combination of pure bending and Lorentz loading to ≥ 0.92% (calculated elastically at the outer tape edge). This significant strain level, and the fact that it is multi-filamentary conductor and available in the reacted and insulated state, makes DI-BSCCO HT-NX highly suitable for very high-field solenoids, for which high current densities and therefore high loads are required to retain manageable magnet dimensions.

Bi-2223 Test Coils for High Resolution NMR Magnets.

Recently, significant improvement in the strain tolerance of Bi-2223 conductor has been achieved by lamination with high strength nickel alloy. The conductor, supplied by Sumitomo Electric and designated Type HT-NX, is now commercially available in lengths sufficient for manufacture of high-homogeneity solenoids. A program to fully exploit the improved conductor properties is now underway at the National High Magnetic Field Laboratory (NHMFL). Five coils are being made, the last of which is to demonstrate an NMR measurement approaching 1 GHz and 1 ppm over 10 mm volume. In so doing, we expect to demonstrate critical current fraction, and strain similar to that expected in 30 T NMR magnets. The coils will be tested inside an existing 16 Tesla large-bore background magnet at the NHMFL. The design of the NMR demonstration coil is presented first, with expected values for field, homogeneity and strain given. A technology development program is then outlined, which includes fabrication of four test coils to test various design features, develop fabrication tooling and train personnel.

Ultra-wide bore 900 MHz high-resolution NMR at the National High Magnetic Field Laboratory.

Access to an ultra-wide bore (105 mm) 21.1 T magnet makes possible numerous advances in NMR spectroscopy and MR imaging, as well as novel applications. This magnet was developed, designed, manufactured and tested at the National High Magnetic Field Laboratory and on July 21, 2004 it was energized to 21.1 T. Commercial and unique homebuilt probes, along with a standard commercial NMR console have been installed and tested with many science applications to develop this spectrometer as a user facility. Solution NMR of membrane proteins with enhanced resolution, new pulse sequences for solid state NMR taking advantage of narrowed proton linewidths, and enhanced spatial resolution and contrast leading to improved animal imaging have been documented. In addition, it is demonstrated that spectroscopy of single site (17)O labeled macromolecules in a hydrated lipid bilayer environment can be recorded in a remarkably short period of time. (17)O spectra of aligned samples show the potential for using this data for orientational restraints and for characterizing unique details of cation binding properties to ion channels. The success of this NHMFL magnet illustrates the potential for using a similar magnet design as an outsert for high temperature superconducting insert coils to achieve an NMR magnet with a field >25 T.

1 GHz NMR spectroscopy: innovation in magnet technology.

The present period is one of rapid development and major extension of the technology for high resolution and solid state NMR spectrometer magnets. Programs which have already been initiated have as their objective proton frequencies of 1 GHz and greater, eventually requiring HTS superconductors. These magnets will contain inner coils containing HTS conductors, surrounded by a set of relatively large coils fabricated with metallic superconductors. These coils represent a major extension of the adiabatically stable magnet technology that has evolved to address the performance issues posed by this type of magnet. The developments which are desirable for these large magnets are identified to include tough epoxy, interface to and thermal performance of external reinforcement, and high strength-high current density metallic superconductor.