Ryoichi Hirose

Operation of a 920-MHz high-resolution NMR magnet at TML

A 920-MHz high-resolution NMR spectrometer has been operating at the Tsukuba Magnet Laboratory (TML) since April 2002. It has proved its effectiveness by determining the 3-D structures of protein molecules. To accelerate studies in structural biology and solid-state NMR, a second high-field NMR magnet was developed and installed at TML. Although its basic design was the same as that of the first magnet, some improvements were made. For the innermost coil, a 16%Sn-bronze-processed (Nb,Ti)/sub 3/Sn conductor was employed. The increase in the critical current density above that of a 15%Sn-bronze-processed (Nb,Ti)/sub 3/Sn conductor made it possible to reduce the conductor size from 3.5 mm /spl times/ 1.75 mm in the first magnet to 2.80 mm /spl times/ 1.83 mm in the second. At the same operating current of the first magnet, the second magnet is expected to operate at 930 MHz. The liquid helium reservoir and the superfluid helium cooler, which were separated in the first system, were united in the same chamber in the new magnet. The latter magnet was energized up to 21.9 T without quenching in March 2004 and has operated in a persistent-mode at that field. It will be utilized mainly for solid-state NMR measurements.

Persistent-mode operation of a 920 MHz high-resolution NMR magnet

Development of a high-field NMR magnet has been underway at the Tsukuba Magnet Laboratory of the National Institute for Materials Science. The magnet succeeded in a persistent-mode operation at 21.17 T in December 1999. A 283-day long-term operation was carried out from October 2000 to August 2001. It included a persistent operation at 21.6 T (920 MHz) for 108 days. This was the highest field that the superconducting magnets have ever achieved in a persistent operation. Field decay was less than 2 Hz/h. Field homogeneity after correcting with superconducting shim coils were less than 0.1 ppm in a sample volume. These results confirmed that this magnet had been successfully developed as a high-resolution NMR magnet.

Development and operation of superconducting NMR magnet beyond 900 MHz

As a milestone in the 1-GHz NMR magnet project being carried out at the Tsukuba Magnet Laboratory, a 900-MHz class NMR magnet was successfully manufactured and operated in December 1999. The developed magnet is made of 15%Sn-bronze-processed (Nb,Ti)/sub 3/Sn, Ta-reinforced (Nb,Ti)/sub 3/Sn, and NbTi conductors. The room temperature bore of the cryostat is 54 mm is diameter. All the coils are cooled with pressurized superfluid helium. The magnet generated a field of 21.20 T in a driven mode and then operated in a persistent mode at 21.17 T corresponding to a proton NMR frequency of 902 MHz. The field may be raised to the range of 21.6 T (920 MHz) in the near future.

Development of a Superconducting Magnet for High Magnetic Force Field Application

Laboratory size superconducting magnets to generate a magnetic force field of 1500 T2 /m in a 40 mm and 50 mm diameter room temperature bore have been developed. In order to generate such a high magnetic force field, a superconducting magnet is combined with main coils and a reverse coil. The magnet can be operated in persistent mode and the field decay is less than 1 ppm/h, which means that the sample can be kept in a micro gravity environment for more than two years. This magnet will be used in various applications in the field of micro gravity application, such as protein crystal growth.

Development of 7 T Cryogen-free Superconducting Magnet for Gyrotron

We developed a special type of 7 T 240 mm vertical bore cryogen-free superconducting magnet system, which will be used for gyrotron. The magnet system consists of three sets of coils which are charged separately. A set of main coils is wound with NbTi conductor and produces 7 T at the center of the bore tube. A set of gun coils is also wound with NbTi conductor and located below the main coil. It produces up to -1.4 T at a lower part of the bore tube and controls the magnetic field where a gun is located. A set of sweep coils are located inside of the main coil. The sweep coil produces only +/- 0.2 T but is charged and discharged within several seconds so as to control electron trajectory. To avoid quench with the rise of the temperature from the large AC loss, this set of coils are wound with Nb3Sn conductor. Also to reduce the induced current in the main coil, the sweep coil is actively shielded. This magnet system will contribute to the fast control of the gyrotron oscillation frequency.

Quench analysis of multisection superconducting magnet

The numerical quench simulation code includes the effect of the filament coupling loss. We apply this simulation code to two multisection high field magnets. In this paper we describe the modified quench simulation code which includes the effect of filament coupling loss and make comparisons between the experimental and analytical results.<<ETX>>

Fabrication Test of YBCO Coil and Multi-Tape Conductor

A testing coil composed of six pancake-coils with a YBCO coated conductor has been fabricated and its superconducting properties have been investigated. The resulting coil has generated magnetic fields up to 0.65 T at 65 K in zero external magnetic field. In order to enhance capability for transporting current of YBCO coil, superconducting behavior of the multi-tape YBCO conductor has also been investigated. The critical current of the conductor that is formed by bundling two tapes has practically achieved the sum of the critical currents.

High intensity combustion of coal for application to a blast furnace

A 1.2 MW tunnel furnace has been used to evaluate combustibility of pulverized coals under the same firing conditions as that of a blast furnace. The coals used contain a proximate volatile matter of 20 to 40%. The combustion air velocity is 250 m/sec at 1200°C and the excess air ratio ranged from 1.6 to 2.5. The heating rates attained were approximately 1.0–1.5×10 6 K/sec. The maximum flame temperature was measured at 2020°C by a two-color pyrometer. Ash or titanium was used as a tracer and gas analysis was used to evaluate the combustibility taking account of distributions of velocity and CO 2 concentration in the furnace. The fractions of coal burned on the centerline of the furnace in about 6 msec ranged from 69 to 83% (d.a.f.). The combustion efficiencies defined by CO 2 production under usual blast furnace conditions were 62 to 93% at the position where the combustion of oil was completed. Combustibility in the initial region which corresponds to a raceway in the blast furnace, was strongly affected by the devolatilization process. The residence time in the raceway is insufficient to completely oxidize the residual char. Combustibility improved with increased volatile matter content in the raw coal, residence time, excess air ratio and combustion air temperature. The injection position had a large effect on the combustibility for the 30–35% volatile coal. Ignition and devolatilization were more rapid with an increase in the combustion air temperature. It was found that the firing conditions with rapid heating, high temperature and strong turbulent flow significantly enhanced the combustibility of pulverized coal compared with the previous result in a jet-stirred reactor in which combustion efficiencies of 60 to 70% were obtained in 10 to 20 msec.

Development of Novel Spectroscopic Magnet Combining Mass Spectroscopy With Nuclear Magnetic Resonance

We developed a superconducting magnet which is suitable for a novel spectroscopy. The methodology of the spectroscopy was suggested by Fuke. This enables to combine NMR (Nuclear Magnetic Resonance) spectroscopy with mass spectroscopy. In order to realize the spectroscopy, the magnet needs two homogeneous regions of 12 T and 4 T, respectively. The field gradient between two regions is required to be high enough. The coil structure is robust against high stress due to such an asymmetric field. The magnet is shielded actively and has a horizontal access room temperature bore of 155 mm diameter.

Development of Two Types of Cryogen Free Superconducting Magnets (5T-ϕ300min and 10T-ϕ100mm)

An Ic-B-T characteristic (critical current vs. magnetic field at various temperatures) for multifilamentary NbTi superconducting (SC) wire has been measured by using a conduction cooled critical current measurement apparatus up to 300A and up to 5T, in the temperature range from 5K to 7.5K.