著者

遠藤 忠 小柳 正男

出版者

CRYOGENICS AND SUPERCONDUCTIVITY SOCIETY OF JAPAN

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.15, no.1, pp.12-21, 1980-02-25 (Released:2010-02-26)

参考文献数

35

---

The national voltage standard has recently been maintained by using the Josephson effect in more than ten countries. The voltage standard had been maintained by the standard cell for a long time. The stability of the voltage standard has been improved by the introduction of the Josephson voltage standard. The Josephson voltage standard is based on the constancy and universality of the fundamental physical constant 2e/h. The adopted value of 2e/h in ETL is 483 594GHz/V. The accuracy of the Josephson voltage standard is 10-7 to 10-8 in the practical use. The further improvement of the accuracy would be expected. The commercial Josephson voltage standard system will be widely used in near future.In this article, the above profile of the Josephson voltage standard is described.

著者

北村 泰一

出版者

CRYOGENICS AND SUPERCONDUCTIVITY SOCIETY OF JAPAN

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.15, no.1, pp.38-47, 1980-02-25 (Released:2010-02-26)

参考文献数

5

---

Some technical problems are described concerning the field measurements of the geomagnetic field by using SQUID magnetometer.In the natural circumstances, the atmospheric temperature change, wind, rain and even the thunder activities bring several disturbances into the measurements of the geomagnetic field using SQUID. Among them, some of the troubles are attributed to the lower slew rate of the SQUID electronic circuits compared to that of the phenomena. Others come from the temperature effect of, also, the circuits, in particular, from the amplitude change of the RF oscillator due to the temperature change.Several examples observed at Mt. ASO (lower magnetic noise site) are shown. A comparison of small geomagnetic changes at Mt. ASO with that at Syowa base, Antarctica, is made, and the coincidental events are found between the two sites separated more than 10, 000km.

著者

井上 廉 坂井 義和 浅野 稔久 前田 弘

出版者

CRYOGENICS AND SUPERCONDUCTIVITY SOCIETY OF JAPAN

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.30, no.4, pp.163-170, 1995-04-25 (Released:2010-02-26)

参考文献数

14

被引用文献数

2 2

---

Recently, we successfully developed a new Cu-Ag microcomposite alloy with a promising combination of high mechanical strength and high electrical conductivity. When a Cu-16 at% Ag alloy ingot was cold-worked into a wire or a sheet with several times of intermediate annealing at 350-450°C, it shows high conductivity of 75-83% IACS and a high tensile strength of 0.7-1.1GPa at room temperature. These values are superior to those of Cu-Nb microcomposite alloy. The Cu-Ag microcomposite alloy shows excellent mechanical strength with cold work of over 93% areal reduction ratio, while a very heavy cold work of more than 99.97% areal reduction ratio is necessary for realizing such mechanical strength in the Cu-Nb microcomposite. A further advantage of the Cu-Ag microcomposite is easy casting of the alloy ingot, resulting in excellent homogeneity of the microstructure and, therefore, the properties in the alloy wire and sheet. We wound the Cu-Ag microcomposite alloy wire into several pulsed magnets. One of them generated non-destructively 73.4T with duration time of 5msec in a 10mm bore. An other one generated non-destructively 65.3T with duration time of 100msec in a 16mm bore. The feasibility study of the Cu-Ag microcomposite alloy sheet as Bitter magnet sheets is progressing now in collaboration with the Francis Bitter National Magnet Laboratory and the National High Magnetic Field Laboratory. A steady field of 35.2T could be generated by inserting the Cu-Ag microcomposite alloy Bitter sheets into the highest-field region in Hybrid III of FBNML. These pulsed fields and the steady one are world records as of this writing.

著者

宇佐美 貴史 吉田 隆 一野 祐亮 菅野 未知央 町屋 修太郎 衣斐 顕 和泉 輝郎

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.51, no.6, pp.259-264, 2016

---

<p>The strain effect of REBa₂Cu₃O<i>_y</i> (REBCO: RE = Y, Gd, Sm)-coated conductors (CCs) on critical current (<i>I</i>_c) is one of the most fundamental factors for superconducting coil applications. In this study, we aim to clarify the effect of artificial pinning center shapes on the strain effect in BHO-doped GdBCO CCs_. To achieve this, we fabricated a Pure-GdBCO CC, a BHO nanorod-doped GdBCO CC and a multilayered-GdBCO (ML-GdBCO) CC, and carried out bending tests. As the result, the strain dependence of <i>I</i>_c for each CC showed an upward convex and the<i> </i>peak strain of the BHO-doped GdBCO CC shifts towards the compressive strain independent of the BHO shapes. In addition, the strain sensitivity of <i>I</i>_c in the GdBCO CCs including BHO becomes smaller. To clarify the difference between the strain sensitivity of <i>I</i>_c and the peak strain among the CCs, we evaluated the residual strain and the slopes of the internal lattice strains against the applied tensile strain (<i>&beta;</i>). From this measurement, the residual strains for the Pure-GdBCO CC and the ML-GdBCO CC were almost the same. In addition, there was no change in the <i>&beta;</i> value between the Pure-GdBCO and ML-GdBCO CCs. These results suggest that the changes in peak strain and strain sensitivity were not related to the internal lattice strain.</p>

著者

島﨑 毅

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.56, no.1, pp.3-11, 2021-01-20 (Released:2021-01-28)

参考文献数

40

---

The temperature is one of the important parameters, both in experiments and analysis, in cryogenic research and development. Recently the definition of the unit of temperature, Kelvin, which is one of the seven basic units in the International System of Units (SI) was redefined along with three other basic SI units. An outline of the redefinition of the Kelvin and its background are presented. Despite the historic redefinition of the Kelvin, practical cryogenic thermometry is not, and will not be, affected at least for a while. Practical cryogenic thermometry is based on the International Temperature Scales (ITSs). The definitions of the ITSs were not changed after the redefinition of the Kelvin. The relationship between the ITSs and the Kelvin definition, and the characteristics of thermodynamic thermometry are also presented.

著者

大塚 泰一郎

出版者

CRYOGENICS AND SUPERCONDUCTIVITY SOCIETY OF JAPAN

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.34, no.8, pp.385-394, 1999-08-25 (Released:2010-02-26)

参考文献数

3

---

The reversibility of the magnetic behaviour of superconductors assured by the Meissner effect allows the application of thermodynamics to analyse the macroscopic properties of superconductors. In this second lecture, the fundamentals of electromagnetism and thermodynamics will be reviewed and applied to the analysis of superconductive phenomenon.

著者

白井 康之 横山 彰一

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.53, no.4, pp.210-217, 2018-07-20 (Released:2018-08-03)

参考文献数

34

---

We have been developing a conduction cooled HTS-MRI that is driven by a power supply in order to solve the long-lasting attenuation of the screening current induced on superconducting tapes at the time of initial excitation and the difficulty with REBCO tape superconducting junctions, as well as a superconducting switch for persistent current operation. A power supply system consisting of two exciters, one for charging and discharging and the other for holding the magnet current, is proposed and developed. The supply system is equipped with a control block to compensate the magnetic field deviation caused by the screening current. We carried out a magnetic field stability experiment using a 32-H HTS-MRI magnet excited by the power supply system proposed which was equipped with specially designed micro-current control.

著者

押川 巧 船越 義彦 今岡 宏志 井口 将秀 櫻井 武尊 中平 昌隆

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.54, no.6, pp.452-458, 2019-11-20 (Released:2019-11-29)

参考文献数

13

---

High nitrogen austenitic stainless steel forgings with heavy thickness and complex configuration are used for the ITER TF coil case. In the forging process for high nitrogen austenitic stainless steel, it is generally difficult to simultaneously obtain good ultrasonic attenuation, the required mechanical properties and the desired near-net shape. Accordingly, JCFC undertook development of an innovative forging method to form the near-net shape of the product, through consideration of possible methods and laboratory testing. By applying JCFC’s innovative method in trial manufacturing commissioned by QST, it was confirmed that the resulting forgings had material properties that satisfy ITER requirements and were also formed into a near-net shape. Subsequently, JCFC manufactured the actual forgings.

著者

沼澤 健則

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.55, no.1, pp.53-58, 2020-01-20 (Released:2020-01-28)

参考文献数

7

被引用文献数

1

---

A new Active Magnetic Regenerator (AMR) cycle has been proposed and tested. We developed a four-unit AMR (fAMR) driving cycle consisting of four AMR units and two magnets. f-AMR operates a pair of magnetization and demagnetization processes in an AMR cycle simultaneously, and as a result, four AMR cycles can be continuously operated. The merits of the fAMR cycle are: four times larger cooling capacity, reducing the thermal loss of heat transfer fluid, a simple mechanism to provide a larger temperature span, feasibility as a thermal device, and expandability of the AMR unit number. Experimental results at room temperatures showed unique properties of f-AMR. Using a weak 0.75 T permanent magnet, the largest temperature span reached to 20 deg. using Gd spheres with a 0.4 mm diameter and COP was larger than 1.0 for a temperature span of 10 deg. We have started to use the f-AMR cycle for a hydrogen re-condensation system at 20 K. A hybrid cooling system using f-AMR and GM cycles will be able to pursue a target of 15% Carnot for hydrogen re-condensation liquefiers.

著者

長﨑 陽 鎌田 弦 刀 友基 佐々木 修平 宮城 大輔 津田 理

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.55, no.2, pp.117-124, 2020-03-20 (Released:2020-03-27)

参考文献数

12

---

This paper discusses the demonstration of a stable levitation (SL) system for a magnetic levitation type seismic isolation device using a high-temperature superconducting (HTS) bulk. The SL system utilizes a restoring force between an HTS bulk and permanent magnet (PM) to maintain the stable levitation of a base-isolation object. We first measured the restoring force between the HTS bulk and PM, and then demonstrated the performance of the SL system using a magnetic levitation type seismic isolation model device with a radial arrangement of HTS bulks and a PM rail. The SL system with the HTS bulk can reduce small vibration and displacement during the normal period of operation without experiencing a large disturbance. We also demonstrated that, when a large disturbance was applied, the transmission of horizontal vibration to the base-isolation object via the SL system was eliminated by decoupling the magnetic coupling between the HTS bulk and PM. Furthermore, the vibration transmissibility at any vibration frequency to the base-isolation object was reduced by incorporating an HTS bulk damper and eddy current damper in the model device. These results suggest that a SL system used together with an HTS bulk can realize both the stable levitation of a base-isolation object during the normal period of operation as well as the elimination of the horizontal vibration transmission when a large vibration is applied.

著者

畑 徹

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.54, no.5, pp.392-397, 2019-09-20 (Released:2019-11-12)

参考文献数

13

著者

村上 雅人

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.42, no.12, pp.414-418, 2007-12-25 (Released:2008-10-28)

参考文献数

9

被引用文献数

2 1

---

In this article, the mechanism of stable levitation by bulk high-temperature superconductors is presented. Superconductor levitation is fascinating and thus displayed in various demonstrations. In general, superconductor levitation is explained in terms of the Meissner effect, which is not applicable in the case of levitating a permanent magnet by Y-Ba-Cu-O cooled with liquid nitrogen. For stable levitation in free space, the restoring forces must act on the levitated object in three rectangular directions, which cannot be fulfilled by simple diamagnetic levitation like that found with the Meissner effect. A pinning effect that fixes quantized fluxoids is the source of such restoring forces, and therefore, superconductor levitation is stabilized by flux pinning.

著者

門奈 五兵

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.2, no.3, pp.1-6, 1967-10-10 (Released:2010-02-26)

参考文献数

13

著者

三戸 利行

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.50, no.12, pp.566-574, 2015-12-25 (Released:2016-02-01)

参考文献数

5

被引用文献数

1 3

---

The Large Helical Device (LHD) is an experimental heliotron-type fusion plasma which consisting of a complete superconducting magnet system cooled by a helium refrigerator having a total equivalent cooling capacity of 9.2 kW@4.4 K. Eighteen plasma experimental campaigns have been performed successfully since 1997, with a high reliability of 99%. Seventeen years have passed since beginning system operation. During the operational history, appropriate improvements have been implemented to prevent serious failures and to pursue further reliability. The operational history of the LHD cryogenic system is reported along with improvements that have been made to the system.

著者

齋藤 明子 加治 志織 小林 忠彦 中込 秀樹

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.50, no.2, pp.88-95, 2015-02-25 (Released:2015-04-06)

参考文献数

40

被引用文献数

1

---

The development of magnetic refrigerants and basic research on active magnetic regenerative (AMR) refrigeration at room temperature were performed. Temperature differences between the hot and cold ends of the AMR unit of more than 45 degrees, and achieving the lowest temperature of minus 10 degrees were obtained by operating the AMR cycle with a NdFeB Halbach-type permanent magnet and spherical-shaped GdY magnetic refrigerants. In the case of the La(Fe,Co,Si)13 compound, the temperature difference between the ends of the AMR unit reached only 21 degrees. This is mainly attributed to the fact that larger specific heat provides smaller temperature changes in the magnetocaloric effect even if the La(Fe,Co,Si)13 compound shows larger magnetic entropy change than Gd alloys. At the same time, large specific heat is effective for load characteristics. Model calculations indicated that multi-layered magnetic refrigerants whose magnetic transition temperatures are tailored to the temperature gradient in the AMR unit improve both temperature difference and load characteristics. Ideal design for achieving optimized heat flow and regeneration leads to the room-temperature application.

著者

緒形 俊夫 石川 圭介

出版者

CRYOGENICS AND SUPERCONDUCTIVITY SOCIETY OF JAPAN

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.21, no.2, pp.99-103, 1986-04-25 (Released:2010-02-26)

参考文献数

9

被引用文献数

1 1

---

Measurements were made on the temperature rise of tensile test specimens of austenitic stainless steels undergoing plastic deformation and discontinuous flow in normal liquid helium and superfluid helium. As the strain rate increased, the ultimate tensile strength and elongation decreased and the temperature rise increased. Compared with the results in normal liquid helium, the frequency of stress drop increased and the temperature rise was suppressed in superfluid helium.

著者

青井 良文 上田 祐樹

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.43, no.12, pp.556-560, 2008 (Released:2009-03-02)

参考文献数

9

---

A gas in a tube spontaneously oscillates when the temperature ratio between the tube ends exceeds a critical value. This spontaneous gas oscillation is applied to a liquid helium level finder. In the present study, to design a liquid nitrogen level finder using spontaneous gas oscillation, the critical value of the temperature ratio causing spontaneous gas oscillation for the case of nitrogen gas was numerically investigated. It was found that a tube in which an array of narrow circular tubes is located can work as a liquid nitrogen level finder. Hence, a tube with an array of narrow tubes was constructed and the liquid level of nitrogen put into a vessel was measured with the constructed tube. The measurements also demonstrated that the tube can work as a liquid nitrogen level finder.

著者

小森 彰夫

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.45, no.1, pp.1, 2010 (Released:2010-04-02)

著者

相山 義道 梅田 政一

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.36, no.10, pp.576-583, 2001

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The historic story of the superconducting (SC) magnet for MHD ETL Mark V Facility (cf. Fig. 1) is presented. This SC magnet was developed in the MHD Project (1966-75), which was one of the first MITI/AIST Large-Scale R & D Projects and the first national project for superconductor applications in Japan. This SC magnet had been the largest in Japan through 1982 when the Japanese LCT coil was made by JAERI. It was completed after many difficulties, some fatal and some trivial, because of a lack of knowledge, before it could generate maximum magnetic field 7T with stored energy 65MJ in 1973. Because technological problems had piled up and because no management know-how of national projects on technology development had been accumulated before then in the forefront of worldwide technological advances, &ldquo;step by step&rdquo; advances and &ldquo;trial and error&rdquo; attempts in the progress of the project had to be done over again. The paper is divided into three parts. Part I (Ref. 12) described the magnet design concept and the conductor tests. In this part II, the failures in exciting the magnet, the repair of the magnet system and the re-challenge with success are described.

著者

相山 義道 梅田 政一

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.36, no.9, pp.516-524, 2001

被引用文献数

1

---

The historic story of the superconducting (SC) magnet for MHD ETL Mark V Facility (cf. Fig. 1) is presented. This SC magnet was developed in the MHD Project (1966-75), which was one of the first MITI/AIST Large-Scale R & D Projects and the first national project for superconductor applications in Japan. This SC magnet had been the largest in Japan through 1982 when the Japanese LCT coil was made by JAERI. It was completed in 1973 after many difficulties, some fatal and some trivial, because of a lack of knowledge, before it could generate maximum magnetic field 7T with stored energy 65MJ. Because technological problems had piled up and because no management know-how of national projects on technology development had been accumulated before then in the forefront of worldwide technological advances, &ldquo;step by step&rdquo; advances and &ldquo;trial and error&rdquo; attempts in the progress of the project had to be done over again. The paper is divided into three parts. Part I describes the process of determining the specifications of the magnet and the conductor tests before the magnet was manufactured.