低温工学
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51 巻 , 7 号
選択された号の論文の9件中1~9を表示しています
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  • 大森 隆夫
    51 巻 (2016) 7 号 p. 312-322
    公開日: 2016/11/04
    ジャーナル フリー

    The calorimeter is used to test the thermal performance of multilayer insulation (MLI). The data obtained by the calorimeter installed in a laboratory must be utilized to estimate the thermal performance of MLI fabricated in the actual cryostat for superconducting magnets or the storage vessel for low-temperature liquefied gas. If MLI is fabricated in an actual cryostat so as to be in the state of self-compression, the non-dimensional parameter P* of the compression pressure between the adjacent layers plays an important role as an experimental condition. In order to design a calorimeter, it is necessary to pay attention to its apparent thermal conductivity, which is lowest among all insulation materials and has extremely large anisotropy. In view of this, the MLI sample must be fabricated so that it covers the entire surface of the calorimeter test cylinder, and the cross-section of MLI at its ends must not be exposed to hot surfaces or shield plates. Some amount of distortion or small steps on the cold surface where the MLI is wrapped may cause wrinkles in the MLI; at which time it becomes impossible to determine the value of P*. A new calorimeter utilizing a small cryo-cooler and heat-flow meter is shown. This calorimeter is expected to enable to allow experiments to proceed efficiently by eliminating the burden of handling liquefied gases, like liquid helium.

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  • 西島 元
    51 巻 (2016) 7 号 p. 329-334
    公開日: 2016/11/04
    ジャーナル フリー

    We have successfully upgraded the a 920-MHz (21.6 T) nuclear magnetic resonance (NMR) superconducting magnet to 1020 MHz (24.0 T). The newly developed 3.6-T (Bi,Pb)2Sr2Ca2Cu3O10 (Bi-2223) innermost coil, which was made of Cu-alloy laminated Bi-2223 tapes, was installed instead of a Nb3Sn innermost coil. The upgrading project was a technical challenge for a Bi-2223 high-Tc superconductor, not only from a high-field application point of view, but also from the perspective of homogeneous and stable field generation. In this review, the development of the a Bi-2223 innermost coil and the outline for upgrading are introduced. Serious damage caused by the Great East Japan Earthquake is also introduced. Some major accomplishments are shown.

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  • 高橋 雅人, 松本 真治
    51 巻 (2016) 7 号 p. 335-341
    公開日: 2016/11/04
    ジャーナル フリー

    Superconducting magnets are widely used in NMR spectrometers in order to achieve higher magnetic-field strength and stability. Especially, the magnetic-field stability of low-temperature superconducting (LTS) magnets commonly used is realized using a persistent current mode. Recent progress in high-temperature superconductors (HTS) and magnet technologies is promoting the development of magnets to exceed 1 GHz (23.5 T) limited by the low critical-current density of LTS in a high- magnetic field. However, there is still no superconducting joint for HTS to enable a persistent current mode. We have developed a 1,020 MHz (24.0 T) NMR using a Bi2Sr2Ca2Cu3Ox (Bi-2223) innermost coil with an external power supply. The driven-mode operation of a large-scale magnet for the high-resolution NMR was a new challenge requiring related problems to be investigated. A highly stabilized power supply and equipment for power outage have been developed for the high-resolution solution NMR and long-term operation.

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  • 柳澤 吉紀, 井口 聖威也
    51 巻 (2016) 7 号 p. 342-348
    公開日: 2016/11/04
    ジャーナル フリー

    The world's first Nuclear Magnetic Resonance (NMR) system with an operating frequency above 1 GHz was developed and operated at the National Institute for Materials Science (NIMS) during 2014–2015. The Nb3Sn innermost coil of an existing 920 MHz (21.6 T) NMR magnet was replaced with a Bi-2223 layer-wound coil, upgrading the magnet to 1.03 GHz (24.2 T). At 1.02 GHz (24.0 T), shimming started to achieve the homogeneous magnetic field required for NMR measurements. However, large magnetic-field inhomogeneity appeared that was capable of being compensated using the superconducting (SC) and room temperature (RT) shim coils installed. We used a powerful and fast-acting shimming method that combines ferromagnetic shim, SC shim and RT shim to compensate the inhomogeneity. This achieved effective compensation of the magnetic-field inhomogeneity, subsequently leading to an excellent NMR resolution test result of 0.7 ppb (0.7 × 10-9). This NMR resolution will enable NMR measurement of a membrane protein sample.

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  • 野口 隆志
    51 巻 (2016) 7 号 p. 349-356
    公開日: 2016/11/04
    ジャーナル フリー

    The pressurized superfluid cooling system has been completed a final adjustment with the 920 MHz NMR in 2002. The superfluid cooling system used this time had been using for the 920 MHz NMR from 2002 to 2007. The first cooling system was able to automatically control the cooling of the superconducting coil to 1.55 K +/- 5 mK, and it was possible to operate remotely via the internet. However, in case of the 1020 MHz NMR system, the heat load is increased to approximately four times more than originally planned value, was forced to change of the components during the cooling operation. Along with it, always should be cooling operation in a transient state, operating procedures were also changed significantly. Measurement system that shows an abnormal behavior by aging was used for state diagnosis only. Therefore, the cooling system was operated manually under the supervision. Fortunately, the cooling system had many measurement points for during test operation, so there was no trouble in determining the transient state. As a result, temperature of the superconducting magnets for 1020 MHz NMR had been kept to 1.72 K +/- 20 mK.

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  • 端 健二郎, 大木 忍 , 後藤 敦, 清水 禎
    51 巻 (2016) 7 号 p. 357-360
    公開日: 2016/11/04
    ジャーナル フリー

    The stability and homogeneity of a 1,020 MHz NMR magnet were evaluated by NMR measurements. The drift of the magnetic field was initially ±0.8 ppm/10 h without using the NMR lock operation, and was then stabilized to less than 1 ppb/10 h using the NMR lock operation. The full width at half-maximum of the 1H spectrum taken for 1% CHCl3 in acetone-d6 was as low as 0.7 Hz (0.7 ppb). These results indicate that the specifications of the 1,020 MHz NMR magnet satisfy the requirements for NMR measurements. In order to demonstrate the efficiency of a high magnetic field, some solid-state NMR spectra were measured at 24.0 T.

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