Hashimoto, Shunsuke*; Nakajima, Kenji; Kikuchi, Tatsuya*; Kamazawa, Kazuya*; Shibata, Kaoru; Yamada, Takeshi*
Journal of Molecular Liquids, 342, p.117580_1 - 117580_8, 2021/11
Quasi-elastic neutron scattering (QENS) and pulsed-field-gradient nuclear magnetic resonance (PFGNMR) analyses of a nanofluid composed of silicon dioxide (SiO) nanoparticles and a base fluid of ethylene glycol aqueous solution were performed. The aim was to elucidate the mechanism increase in the thermal conductivity of the nanofluid above its theoretical value. The obtained experimental results indicate that SiO particles may decrease the self-diffusion coefficient of the liquid molecules in the ethylene glycol aqueous solution because of their highly restricted motion around these nanoparticles. At a constant temperature, the thermal conductivity increases as the self-diffusion coefficient of the liquid molecules decreases in the SiO nanofluids.
Matsuda, Yasuhiro*; Her, J.-L.*; Michimura, Shinji*; Inami, Toshiya; Ebihara, Takao*; Amitsuka, Hiroshi*
JPS Conference Proceedings (Internet), 3, p.011044_1 - 011044_6, 2014/06
Synchrotron X-ray absorption spectroscopy of CeRhSi has been performed in pulsed high magnetic fields of up to 32 T. The Ce valence is slightly larger than 3+ at 5 K and decreases with increasing magnetic above 20 T. The field-induced valence change seems to correspond to the metamagnetic transition in the magnetization process. This phenomena is similar to our previous result on CeRuSi and seems to be common in Ce-based heavy fermion compounds.
Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Kuga, Kentaro*; Nakatsuji, Satoru*; Michimura, Shinji*; Inami, Toshiya; Kawamura, Naomi*; Mizumaki, Masaichiro*
Journal of the Korean Physical Society, 62(12), p.1778 - 1781, 2013/06
The valence state of Yb ions in - and -YbAlB has been investigated by X-ray absorption and emission spectroscopy at temperatures from 2 to 280 K. It is found that the valence gradually increases with increasing temperature toward 3+ and that the characteristic temperature of the valence fluctuations is about 290 K. We also observe a small increase in the Yb valence ( 0.002) in -YbAlB by a magnetic field of 32 T at 40 K.
Kudo, Yusuke; Sawai, Tomotsugu; Sakurai, Shinji; Masaki, Kei; Suzuki, Yutaka; Sasajima, Tadayuki; Hayashi, Takao; Takahashi, Ryukichi*; Honda, Masao; Jitsukawa, Shiro; et al.
Journal of the Korean Physical Society, 49(96), p.S297 - S301, 2006/12
Installation of ferritic steel tiles was proposed in JT-60U to reduce the toroidal magnetic field ripple and to improve the fast ion loss, which degrades heating efficiency and increases heat load on plasma facing component under large volume plasma operations. We selected a 8Cr-2W-0.2V ferritic steel with the cost-effectiveness, in which concentration limits of activation elements in F82H were relaxed because of the less number of neutron generations from deuterium operations on JT-60U. The fabricated ferritic steel has clear tempered martensitic microstructure, and sufficient magnetic and mechanical properties. The saturated magnetization was estimated to 1.7 Tesla at 573 K, lower than expected, but effectiveness in JT-60U was confirmed by numerical analyses. To research the effect of material conditions, such as microstructure and heat treatment, on saturated magnetization of the ferritic steel based on 8-9Cr is important for the future fusion reactors which will be planned to install the ferritic steel as the in-vessel components.
Kamiya, Junichiro; Ueno, Tomoaki*; Takayanagi, Tomohiro
IEEE Transactions on Applied Superconductivity, 16(2), p.1362 - 1365, 2006/06
Kicker magnets in J-PARC RCS are being constructed at JAERI (Japan Atomic Energy Research Institute) as the extraction pulse magnet. It is designed to have a large aperture in order to accept the maximum beam power 1MW. Therefore the impedance mismatch and fringe field have the large effect on distortion of a flatness of the kicker magnetic field. We examined their effect by the simulation and measurement, and contrived to improve the field flatness. In this paper, we present the features of the RCS kicker systems, describe the magnetic field measurement and improvement, and briefly introduce the field mapping which we are performing now.
Inami, Toshiya; Owada, Kenji; Matsuda, Yasuhiro*; Ueda, Yuji*; Nojiri, Hiroyuki*; Murakami, Yoichi*; Arima, Takahisa*; Ota, Hiroto*; Zhang, W.*; Yoshimura, Kazuyoshi*
Nuclear Instruments and Methods in Physics Research B, 238(1-4), p.233 - 236, 2005/08
Usually, X-ray diffraction experiments under strong magnetic fields are carried out using a superconducting magnet and the maximum field is limited up to 15T. In order to overcome this limitation, we have constructed an X-ray diffraction system combined with a pulsed magnet. The structural phase transition of PrCaMnO around 8 T and the valence transition of YbInCu around 26 T are shown as a demonstration.
Okumura, Susumu; Arakawa, Kazuo; Fukuda, Mitsuhiro; Nakamura, Yoshiteru; Yokota, Wataru; Ishimoto, Takayuki*; Kurashima, Satoshi; Ishibori, Ikuo; Nara, Takayuki; Agematsu, Takashi; et al.
Review of Scientific Instruments, 76(3), p.033301_1 - 033301_6, 2005/03
A magnetic field drift, gradual decrease of the order of 10 in several tens of hours, was observed with the beam intensity decrease in an operation of an azimuthally-varying-field (AVF) cyclotron. From our experimental results, we show that the temperature increase of the magnet iron by the heat transfer from the excitation coils can induce such change of the magnetic field as to deteriorate the beam quality. The temperature control of the magnet iron was realized by thermal isolation between the main coil and the yoke and by precise control of the cooling water temperature of the trim coils attached to the pole surfaces in order to prevent temperature change of the magnet iron. The magnetic field stability of 510 and the beam intensity stability of 2% have been achieved by this temperature control.
Yamamoto, Kazuyoshi; Kumada, Hiroaki; Nakai, Kei*; Endo, Kiyoshi*; Yamamoto, Tetsuya*; Matsumura, Akira*
Proceedings of 11th World Congress on Neutron Capture Therapy (ISNCT-11) (CD-ROM), 14 Pages, 2004/10
A dose distribution considered the tumor cell density distribution is required on the radiation therapy. We propose a novel method of determining target region considering the tumor cell concentration as a new function for the next generation Boron Neutron Capture Therapy (BNCT) dosimetry system. It has not been able to sufficiently define the degree of microscopic diffuse invasion of the tumor cells peripheral to a tumor bulk in malignant glioma using current medical imaging. Referring to treatment protocol of BNCT, the target region surrounding the tumor bulk has been set as the region which expands at the optional distance with usual 2cm margin from the region enhanced on T1 weighted gadolinium Magnetic Resonance Imaging (MRI). In this research, the cell concentration of the region boundary of the target was discussed by using tumor cell diffusion model in the sphere spatio-temporal system. The survival tumor cell density distribution after the BNCT irradiation was predicted by the two regions diffusion model for a virtual brain phantom.
Hayashi, Takao; Nishitani, Takeo; Ishikawa, Masao
Review of Scientific Instruments, 75(10), p.3575 - 3577, 2004/10
Micro fission chambers, which are pencil sized ionization chamber with fissile material inside, to be installed in the vacuum vessel as neutron monitor for the International Thermonuclear Experimental Reactor (ITER). The micro fission chamber has been installed inside toroidal field coils in JT-60U, in order to investigate the technical validity as neutron monitor in a magnetic field of about 2 T. Compared with the neutron yield measured by three U fission chambers which are used as neutron monitors in JT-60U, neutron yield measured by micro fission chamber has a good linearity with them. The influence of the magnetic field on the micro fission chamber has not been observed. However improper signals caused by plasma disruption and breakdown event of Neutral Beam Injection were observed, probably due to long wiring between the detector and the preamplifier. Therefore, by enhancement of noise protections, micro fission chambers can be available as neutron monitor for ITER.
Matsuda, Yasuhiro*; Ueda, Yuji*; Nojiri, Hiroyuki*; Takahashi, Toshiharu*; Inami, Toshiya; Owada, Kenji; Murakami, Yoichi; Arima, Takahisa*
Physica B; Condensed Matter, 346-347, p.519 - 523, 2004/04
A very small capacitor bank and miniature pulsed magnets have been developed to perform high-field synchrotron radiation experiments. A 20T pulsed field can be generated using an energy of 1kJ with typical pulse duration about 1ms. Electron spin resonance experiments in millimeter wave range and high-field X-ray diffraction experiments have been done successfully.
Urata, Kazuhiro*; Shinohara, Koji; Suzuki, Masanobu*; Kamata, Isao*
JAERI-Data/Code 2004-007, 45 Pages, 2004/03
As the toroidal magnetic field generated by discrete TF coils involves magnetic field ripple, the fast ion loss is induced to damage vacuum vessel in tokamaks. An idea of ripple compensation using ferromagnetic is proposed. Since low activation ferritic steel have low activation and thermal conduction properties, the ferritic steel is planned to install in tokamak reactors. Installation of ferritic steel plates with toroidal symmetry is effective to compensate ripple, however in the actual devices it is difficult for interference with other components. Besides the first wall shapes are often asymmetric. So it is better to treat toroidal asymmetry to evaluate the ripple induced loss in the actual devices. For the purpose, magnetic field calculation code considering ferritic steel; FEMAG(FErrite generating MAGnetic field)has been speeded up. On the basis of this magnetic field data, OFMC (Orbit Following Monte Carlo) has been upgraded to treat toroidal asymmetry. The use of FEMAG/OFMC, applications to the JFT-2M experiments, and the national centralized tokamak facility are reported.
Okawa, Tomohiro*; Ikegami, Masanori*
Proceedings of 9th European Particle Accelerator Conference (EPAC 2004), p.1342 - 1344, 2004/00
The accelerators for the High-Intensity Proton Accelerator Facility Project, J-PARC, consist of a 180-MeV linac, a 3-GeV RCS (Rapid Cycling Synchrotorn), and a 50-GeV MR (Main Ring). L3BT is a beam transport line from the linac to the RCS. To meet the requirement for the beam loss minimization, the L3BT does not only connect the linac to the 3GeV RCS, but also modifies the linac beam to be acceptable for the RCS. The required beam parameters at the injection point of the RCS are momentum spread 0.1 and transverse emittance 4 mmmrad. To achieve these beam qualities, the L3BT should have following functions: momentum compaction, transverse halo scraping and beam diagnostics. In this paper, results of the design and beam simulation of the L3BT are presented.
Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki
Physics of Plasmas, 10(9), p.3512 - 3520, 2003/09
no abstracts in English
Yoshida, Kiyoshi; Isono, Takaaki; Sugimoto, Makoto; Okuno, Kiyoshi
JAERI-Data/Code 2003-014, 38 Pages, 2003/08
In case of designing a superconducting coil (SC), one must calculate a magnetic field (B) and its inductance (L) many times in order to arrange proper design parameters of SC because there are many design parameters to evaluate. SC cannot be designed by the optimum condition if a B and L can't be computed easily. When SC is energized, measurement values of B and L are very well agreed with calculated values. The B and L of the coil that doesn't contain a ferromagnetic material can be calculated by the numerical integration. The analytic method were developed and established in 1970's. This paper shows the calculation program COIL that has been developed by applying this analytic method in JAERI. COIL is qualified by the comparison between measured and calculated values in case of several real SC. COIL is specified to analyze SC of tokamak device. Even for a complicated tokamak device, B and L can be calculated in several minutes by the high performance of the recent personal computer. COIL contributes to design SC for ITER and others.
Meigo, Shinichiro; Noda, Fumiaki*; Fujimori, Hiroshi*; Ikeda, Yujiro
Proceedings of ICANS-XVI, Volume 3, p.967 - 976, 2003/07
In J-PARC project, spallation target is irradiated by 3 GeV proton beam of 1 MW. Due to hands on maintenance for the proton beam lines, loss of proton beam is limited less than 1 W/m. Since it is difficult to predict the phase space distribution of the proton beam, we decided that the beam line have to be larger acceptance for 324 mrad, which is determined by the collimator located in the synchrotron. Distortion of proton beam is caused by the by the instability of angle at the extraction of 3-GeV synchrotron, miss alignment of the magnet, and un-uniformity of the magnet field. In this study, the distortion is calculated. In order to fit the conditions, the stability of extraction angles should be kept smaller than 0.2 mrad. As for the magnetic field, it is found that the uniformity should be kept better 5x10 and 2x10 for bending and quadruple magnets, respectively. It is also found the error of alignments should be limited smaller than 1.0 mm and 1.0 mrad.
Okumura, Susumu; Arakawa, Kazuo; Fukuda, Mitsuhiro; Nakamura, Yoshiteru; Yokota, Wataru; Ishimoto, Takayuki; Kurashima, Satoshi; Ishibori, Ikuo; Nara, Takayuki; Agematsu, Takashi; et al.
Nukleonika, 48(Suppl.2), p.S35 - S37, 2003/00
In the JAERI AVF cyclotron, unstable phenomena, such as beam intensity decrease, were observed. We found that an increase in temperature of the iron body of the magnet induced the drift of the magnetic field. Stabilization of the iron body temperature was achieved. We have developed a nuclear magnetic resonance (NMR) magnetometer with an accuracy of the order of 10 to measure the stability of the cyclotron magnetic field with a large gradient by using a pair of correction coils to reduce the field gradient and by eliminating the effect of the RF.
Takizuka, Tomonori; Hojo, Hitoshi*; Hatori, Tadatsugu*
Purazuma, Kaku Yugo Gakkai-Shi, 78(9), p.857 - 912, 2002/09
Transport along field lines in magnetic confinement plasmas is reviewed. Collisionless and collisional-diffusive transports are discussed. Because of their fast transport, features of plasmas along field lines are apt to behave nonlocally. A nonlocal phenomenon of scrape-off layer (SOL) and divertor plasmas in a tokamak is introduced, whose asymmetry along field lines is induced by the thermoelectric instability related to the SOL current. A local phenomenon called MARFE can be brought by the strong radiation cooling. The "snake" with nonlocal feature along field lines but with local structure perpendicular to the field is observed in a tokamak core plasma. For mirror-confined plasmas, axial particle losses from the mirror ends, especially pitch-angle-sattering losses into the loss cone and nondiabatic losses due to the breakdown of adiabaticity of the magnetic moment, are also discussed in the relation to nonlocal axial transport.
Takayanagi, Tomohiro; Ikehata, Takashi*; Okumura, Yoshikazu; Watanabe, Kazuhiro; Hanada, Masaya; Amemiya, Toru*; Kashiwagi, Mieko
Review of Scientific Instruments, 73(2), p.1061 - 1063, 2002/02
no abstracts in English
Bizen, Teruhiko*; Tanaka, Takashi*; Asano, Yoshihiro; Kim, D. E.*; Bak, J. S.*; Lee, H. S.*; Kitamura, Hideo*
Nuclear Instruments and Methods in Physics Research A, 467-468(Part1), p.185 - 189, 2001/07
no abstracts in English
Niita, Koji*; Meigo, Shinichiro; Takada, Hiroshi; Ikeda, Yujiro
JAERI-Data/Code 2001-007, 128 Pages, 2001/03
no abstracts in English