Shuichi Kido

Development of Superconducting Split Magnets for NMR Spectrometer

We have developed a high-resolution NMR spectrometer with a superconducting split magnet and a cross-shaped bore. Because of the spatial limitations of the magnets structural design, the split magnet requires many pairs of coils to generate a high magnetic field. For this reason, it is difficult to compare the high stability and homogeneity of its magnetic field to conventional NMR magnets. Therefore, we have developed advanced superconducting magnet technologies and successfully fabricated two types of self-shielded superconducting split-magnet systems: a 7 T (300 MHz) and a 14 T (600 MHz) magnet system. The 300 MHz system consists of 12 NbTi coils with 15 joints and a stored energy of 0.7 MJ; it achieved a field drift of about 0.1 Hz/h in persistent current mode operation. The 600 MHz magnet system consists of 12 Nb3Sn coils and 8 NbTi coils with 53 joints and a stored energy of 10 MJ. Its field drift was less than 1 Hz/h.

Development of Shimming System for a Highly Sensitive NMR Spectrometer With a Superconducting Split Magnet

A highly sensitive NMR spectrometer with a superconducting split magnet and a solenoid-type probe coil is being developed. One of the most challenging tasks is to achieve high homogeneity of magnetic field in a measuring volume with this configuration, because inevitable structural asymmetry and limited production accuracy of the magnet cause larger inhomogeneity of magnetic field compared with a conventional solenoid-type NMR spectrometer. Numerical estimation revealed that field correction capability of conventional shim coils, i.e., superconducting solenoid and saddle coils placed outside main coils, is insufficient for the split NMR magnet. Therefore, we have designed and constructed superconducting shim coils with sufficiently high capability by adopting the following three novel ideas: (1) superconducting shim coils are placed not only outside main coils but also inside them in the vicinity of a measuring volume; (2) superconducting shim coils with ldquoperiodically wavyrdquo shape are utilized to correct non-axial inhomogeneous magnetic field; (3) the current of each superconducting shim coil is independently controlled to correct plural modes of magnetic field simultaneously.

A new magnet configuration for a solution NMR spectrometer

We have developed a new configuration for a high-sensitivity NMR spectrometer, using a superconducting split magnet and a room temperature cross-bore. To achieve higher sensitivity, we selected a solenoid-shaped probe coil; the split-magnet system was adopted to get around the complex probe in the structure. The superconducting split magnet is divided into two multilayer coils, and the vertical bore is located between them. A sample tube is inserted into the vertical bore and a probe system is inserted into the horizontal bore. We have already fabricated these magnet systems in the 300MHz and 600MHz resonance frequency-classes. The systems are composed of a superconducting split magnet for the main field, with superconducting shim coils located inside and outside the split magnet. The 600MHz system has run for more than 13 months with less than 1Hz/h field drift. Recent results showed that the signal to noise ratio of a correlation sample (0.1% ethyl benzene) was 4523 for the 600MHz system with a cryogenic probe system.

Fabrication Process Qualification of TF Insert Coil Using Real ITER TF Conductor

JAEA is fabricating the toroidal field insert coil (TFIC) in cooperation with Hitachi, Ltd. This solenoidal coil has about 50 m of ITER TF conductor wound in a 1.44-m diameter. In preparation for fabricating the TFIC, fabrication trials of windings, removal of Cr plating of the cable and welding of the terminal sleeve were performed for process qualification. The winding trials were accomplished without breaking any of the superconducting strands. In the trials to remove the Cr plating from the cable, HCl-soaked unwoven cloth was used, and the surface of a strand selected from the cable was confirmed by magnification to be free of Cr plating. In trials to fabricate termination, using electron beam welding (of OFHC copper and SS316LN) and fillet-welding (of SS316LN and SS316LN using JK2LB weld wire), tensile tests of the welds were conducted at room temperature and 4 K, and ultimate tensile strength values equivalent to that of the base metal of the weld were obtained. Also these welds passed test items of JIS Z3040 code, so the weld procedures were qualified. During fillet-welding the maximum temperature of the cable under the weld was 120 °C, not high enough to damage the cable. From the results obtained, the main processes involved in TFIC fabrication were established and qualified.

Design and Performance Test of Superconducting Transport Solenoid for D-Line at J-PARC Muon Science Facility

A superconducting transport solenoid for Decay Muon Line (D-line) at J-PARC Muon Science Facility was newly designed and manufactured. It was designed to generate a magnetic field in relatively large region (warm bore diameter 0.2 m), while keeping the same outer dimensions, connection interfaces to the existing refrigerator and the power supply of the previous machine [1-3]. Major changes of both solenoids are the reduction of the central magnetic field, the equipment of a warm bore and the adoption of the high Tc current leads. After the installation to the beam line, the initial cooling test, the excitation test and the emergency shutdown test at the rated current were conducted by KEK in order to confirm cryogenic and magnetic performance. These tests were successfully performed with no damege and indicated the solenoid was precisely manufactured and fulfilled the requirements. The solenoid has been under operation since July, 2015. This report describes the design, the manufacturing process, the magnetic field measurement at room temperature and the results of performance tests conducted by KEK.

Manufacture and Quality Control of Insert Coil With Real ITER TF Conductor

JAEA successfully completed the manufacture of the toroidal field (TF) insert coil (TFIC) for a performance test of the ITER TF conductor in the final design in cooperation with Hitachi, Ltd. The TFIC is a single-layer 8.875-turn solenoid coil with 1.44-m diameter. This will be tested for 68-kA current application in a 13-T external magnetic field. TFIC was manufactured in the following order: winding of the TF conductor, lead bending, fabrication of the electrical termination, heat treatment, turn insulation, installation of the coil into the support mandrel structure, vacuum pressure impregnation (VPI), structure assembly, and instrumentation. In this presentation, manufacture process and quality control status for the TFIC manufacturing are reported.

Field Stability and Homogeneity of 14-T Superconducting Split-Pair Magnet for Highly-Sensitive NMR Spectrometer

We have been developing a novel NMR spectrometer with two special features since 2003; the first is its superconducting split-magnet, and the second is its cryogenic solenoidal probe coil. Thus far, we have successfully developed the magnet with magnetic fields up to 14 T that has excellent field stability and homogeneity. The superconducting split-pair magnet has been operating for over two years without any quenching. This paper describes details on field stability and homogeneity under persistent-mode operation.