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Volume 119, Issue 11
Displaying 1-17 of 17 articles from this issue
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Makoto Katsurai1999 Volume 119 Issue 11 Pages 1275
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSDownload PDF (102K) -
Seiichi Goto1999 Volume 119 Issue 11 Pages 1276-1279
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
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Yoshio Nagayama1999 Volume 119 Issue 11 Pages 1280-1285
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSEquilibrium and MHD stability of spherical torus (ST) are numerically examined using computer codes named 'j-solver', 'balloon' and 'camino'. It is found that the path between the first and the second stable regions in the s-α diagram is wider when the aspect ratio of tokamak is lower. Thus, ST has a good accessibility to the second stable region. It is found that the absolute minimum B is created in the bad curvature region. This result suggests that the second stable ST may be free from the anomalous transport. The feasibility of ST reactor is studied using a mechanical analysis of the center post and the ITER93H scaling. Second stable spherical torus with R0=10m has a potential to be an advanced fuel reactor.View full abstractDownload PDF (1077K) -
Toshiki Takahashi, Yoshiomi Kondoh, Hiromu Momota1999 Volume 119 Issue 11 Pages 1286-1291
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSClassical particle transport in a Field-Reversed Configuration has been studied with a use of plasma ki-netic theory. The distribution functions have been obtained for the plasma particles near the separatrix. The algorithm to determine the ambipolar potential at the mirror point is also presented in this paper.View full abstractDownload PDF (821K) -
Yoshiro Narushima, Tsutomu Takahashi, Yasuyuki Nogi1999 Volume 119 Issue 11 Pages 1293-1299
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSUltra Low Aspect Ratio Tokamaks (ULART) are produced by using a negative-biased theta-pinch device. A slender conducting rod which plays a role of a toroidal field coil is newly installed along a geometrical center axis of the theta-pinch coil. The ULART is quickly formed for about 10μs by applying programmed current flows from three sets of fast banks and a slow bank to these coils and is sustained for about 100μs.
The plasma diagnosed from a magnetic probe array has a low aspect ratio A=1.1 and a poloidal surface with a high elongation ratio κ=10. The safety factor reaches about 30 near the separatrix edge when Ip=280kA flows in the plasma and Itfc=30kA in the conducting rod. A preliminary result on global MHD characteristics of the ULART is also given. The plasma behaves unstable to a vertical displacement and a toroidal n=1 mode. The amplitudes of these modes depend on the values of Itfc, and κ.View full abstractDownload PDF (1194K) -
Naoyuki Fukumoto, Masayoshi Nagata, Tadao Uyama, Toshihide Ogawa, Hiro ...1999 Volume 119 Issue 11 Pages 1300-1305
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSCompact Toroid (CT) injection is considered to be an advanced deep fueling method in tokamaks. We developed a CT injector to investigate the possibility of refueling and density control of tokamak plasmas by CT injection in the JFT-2M tokamak. The velocity of the CT was controllable from 120km/s to 190km/s in the case of CT density-6×1021m-3 by changing the voltage of the acceleration bank. We demonstrated the CT penetration into the central region of OH plasmas at BT=0.8T. The tokamak electron density increased-0.2×1019m-3 at a rate of 2×1021m-3/s and the fueling efficiency was about 20%. The penetration depth into the tokamak magnetic field was determined by the balance between the CT kinetic energy density and the toroidal magnetic field density.View full abstractDownload PDF (1592K) -
Yasuhiro Kagei, Naoyuki Amemiya1999 Volume 119 Issue 11 Pages 1306-1311
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSThe feasibility of superconducting center conductors in spherical tokamaks has been studied. The advantage of superconducting center conductors is evaluated from the view point of loss reduction, increasing q and reduction of required βp-The magnetic field dependence of the critical current density is taken into account. The center conductor is divided radially into several layers, and the operating current density of each layer is optimized. If A_??_1.3 and β_??_0.6, the electric power loss can be reduced by the application of superconducting center conductors where, κ-3 and q-10. In spherical tokamak reactors with low electric power loss, larger q can be attained by the application of superconducting center conductor. In other word, the βp required for the specified q can be reduced.View full abstractDownload PDF (1403K) -
Ritoku Horiuchi, Kazumi Nishimura, Tetsuya Sato1999 Volume 119 Issue 11 Pages 1312-1317
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSThe stabilization of the tilt disruption in field-reversed configurations is investigated by means of a three-dimensional particle simulation. For the case of no ion beam, the tilt instability is stabilized by anchoring ions which exist in the vicinity of the magnetic separatrix. It is found that the tilt growth rate is decreased by injecting an ion beam at the neighborhood of the null point even for plasmas with a small anchoring effect and the beam stabilization effect can be estimated by the total beam current.View full abstractDownload PDF (1486K) -
Yoshinobu Ueda, Yasushi Ono1999 Volume 119 Issue 11 Pages 1319-1323
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSHigh-power heating of spherical tokamaks (STs) has been investigated experimentally by use of plasma merging effect. When two STs were coaxially collided, thermal energy of a colliding ST was injected into a target ST during short reconnection time (Alfven time). Though the thermal energy increment increased with decreasing plasma q value, thermal energy loss during the following relaxation, tended to be smaller with increasing q. The produced high-β STs had hollower current profiles and weaker paramagnetic toroidal field than those of single STs. Those heating properties indicate the plasma merging to be a promising initial heating method of ST plasmas.View full abstractDownload PDF (1004K) -
Shigefumi Okada, Katsuhisa Kitano, Seiichi Goto1999 Volume 119 Issue 11 Pages 1324-1329
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSAdditional heating experiments became to be done on plasmas with field reversed configuration by translating the plasma from its formation region to confinement region. Actually, adiabatic magnetic compression was done on the FRX-C/LSM facility and remarkable heating was observed. On the other hand the confinement time became short. This trend was explained by a model in which the FRC plasma was approximated by a cylinder and taking into account of an empirical scaling law for confinement in the adiabatic compression process. By this model, the confinement time of the FRC plasma in a flux conserver was predicted to become longer by compressing the plasma axially. Experimental apparatus to realize this compression was constructed and the experiment was actually carried out. And the axial compression was verified to be effective to improve the confinement of the FRC plasma.View full abstractDownload PDF (1473K) -
Masato Enokizono, Yutaka Takeshima1999 Volume 119 Issue 11 Pages 1330-1335
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSThis paper presents magnetic properties of electrical steel sheets under DC-biased magnetization. We have prac-ticed measurement of the mixsing flux density between AC flux density and DC flux density (DC-biased flux density) by using the flux meter directly. The specimen was excited by voltage of sinusoidal, triangular and rectangular waves. When the amplitude of AC magnetic flux density was controlled to be constant, it was found that in the case of the rectangular exciting wave, that is, the smallest effective flux density value, the DC-biased flux density was lager than one of the other cases and the iron loss become smallerView full abstractDownload PDF (1706K) -
Masato Enokizono, Syuya Fujiyama, Ichirou Serikawa1999 Volume 119 Issue 11 Pages 1336-1341
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSImproving material characteristics and optimizing technical designs have been studied from the standpoint of efficiency improvement of electrical machinery and apparatus. Unfortunately, the local magnetic properties in the actual core were still not understood fully. On the other hand, we have known concept of the two-dimensional magnetic property. It means the relationship between the magnetic field strength vector H and the magnetic flux density vector B that those are not usually parallel but have the phase angle. Therefore local magnetic properties in an actual constructed core should be measured as a vector relation. This paper presents the local magnetic properties in a three-phase induction motor model core, which are measured with the two-dimensional measurement sensor.View full abstractDownload PDF (2304K) -
Ping Yan, Y. X. Zhou, N. Yoshimura1999 Volume 119 Issue 11 Pages 1342-1348
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSIt is well known that electrical trees are greatly influenced by the morphological structure in crystalline polymers. In this paper, samples of polyethylene films, including low-density polyethylene, linear low-density polyethylene and high-density polyethylene have been crystallized and re-crystallized by annealing. The tree initiation voltages of these samples have been measured. It was found that after re-crystallizing the crystallinity and thickness of lamella increase, while the size of the spherulites hardly changes. It was also found that the tree initiation voltage increases after re-crystallizing. Based on the concept of mean free path in solid dielectric, it was assumed that the increase of tree initiation voltage was inherently related to the decrease of mean free path in the spherulites that was due to the increase of the thickness of lamellae.View full abstractDownload PDF (2541K) -
Analysis of Generation Process of N2(A3∑u+) by Nitrogen Atoms Recombination under High E/n ConditionKeisuke Yamashiro, Motoshige Yumoto, Takao Sakai1999 Volume 119 Issue 11 Pages 1349-1354
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSThe authors have studied on generation process of N2(A3∑u+) by nitrogen atoms recombination in gas discharge under high E/n condition. In this condition, reduced electric field intensity is very high and varies with position, therefore electron energy distribution is not in equilibrium, especially near the cathode region. So, to make sure the assumption, the authors measured spatial distribution of radiation of N2 1st Positive Band and analyzed electron energy distribution by the MCS (Monte Carlo Simulation) in the case of various E/n.
As a result, the experimental distribution had two peaks, one is a small peak around cathode region, the other is large one at the mid region between electrodes. These results were predicted by the MCS. Consequently, it was confirmed that the generation process of N2 (A3Σu+) varies with position under the high E/n condition.View full abstractDownload PDF (1114K) -
Discussion based on the symmetrical effective medium approximation theoryShuhei Nakamura, Tetsuya Tomimura, Goro Sawa1999 Volume 119 Issue 11 Pages 1355-1361
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSAlthough literature on the calculation based on the symmetrical effective medium approximation (EMA) theory by changing the parameters is vast, an overall discussion taking into account the EMA theory is required in order to explain the dielectric properties of the composites, the temperature dependence of them, for example. Changes of dielectric properties and the temperature dependence of them of the composites made of carbon black and polyethylene below the percolation threshold (pc) for the volume fraction of carbon black have been discussed based on the EMA theory. The composite is satisfied with the universal law of conductivity above pc whereas it gives the critical exponent of s=1 for dielectric constant below pc. The rate of the decrement of both % changes of dielectric constant and dielectric loss factor for temperature becomes larger with more the volume fraction below pc. By incorporating the effect of thermal expansion into the EMA theory, the temperature dependence of dielectric properties is successfully explained.View full abstractDownload PDF (1213K) -
Hiroshi Yamamoto, Gaku Obara1999 Volume 119 Issue 11 Pages 1362-1367
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSSr-La M-Type ferrite fine particles were prepared by mechanical compounding using the planetary ball-mill and subsequent heat treatment. This experiment was carried out to investigate the magnetic properties of anisotropic and isotropic sintered magnets used Sr-La M-Type ferrite fine particles prepared by mechanical compounding. The optimum condition of making Sr-La M-Type sintered magnet and some properties of typical specimens are as follows; chemical composition:SrO•5.75Fe2O3; additive: 1.0wt%La2O3; planetary ball-mill condition:300rpm×1h; heat treatment condition: 1100°C×2h; sintering condition: 1225°C×2h. The value of (BH)max for an anisotropic sintered magnet used these powders is obtained 34.5kJ/m3.View full abstractDownload PDF (2216K) -
Yoshio Tanabe, Keiichi Yamamoto1999 Volume 119 Issue 11 Pages 1368-1373
Published: November 01, 1999
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSMagnetic shields made of ferromagnetic materials have been used for many applications but comprehensive study on a shield with rectangular cross section is not carried out. In order to evaluate the accuracy of the FEM, the exact theoretical solution of shielding factor was derived for a double cylindrical shield with different permeability. In the case of the single cylinder, the theoretical and FEM results agreed well but there were some differences between them in the case of the double cylinder.
There are two cases of applying the external magnetic field to the rectangular magnetic shield, that is, perpendicular to the short side and perpendicular to the long side. The measured shielding factor of the former case was higher than that of the latter case. These results were verified by the linear and non-linear FEM calculations. Moreover, penetration of the magnetic field from the tube edge was evaluated.View full abstractDownload PDF (1036K)
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