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Journal Articles

Valence state in Ce-based heavy fermion compounds at high magnetic fields

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 CeRh$$_2$$Si$$_2$$ 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 CeRu$$_2$$Si$$_2$$ and seems to be common in Ce-based heavy fermion compounds.

Journal Articles

Synchrotron X-ray spectroscopy study on the valence state in $$alpha$$- and $$beta$$-TbAlB$$_4$$ at low temperature and high magnetic fields

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

 Times Cited Count:8 Percentile:43.86(Physics, Multidisciplinary)

The valence state of Yb ions in $$alpha$$- and $$beta$$-YbAlB$$_4$$ 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 ($$sim$$ 0.002) in $$beta$$-YbAlB$$_4$$ by a magnetic field of 32 T at 40 K.

Journal Articles

Fabrication of 8Cr-2W ferritic steel tile for reduction in toroidal magnetic field ripple on JT-60U

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.

Journal Articles

Magnetic field measurement of the extraction kicker magnet in J-PARC RCS

Kamiya, Junichiro; Ueno, Tomoaki*; Takayanagi, Tomohiro

IEEE Transactions on Applied Superconductivity, 16(2), p.1362 - 1365, 2006/06

 Times Cited Count:4 Percentile:69.14(Engineering, Electrical & Electronic)

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.

Journal Articles

X-ray diffraction experiments under pulsed magnetic fields above 30T

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

 Times Cited Count:8 Percentile:44.99(Instruments & Instrumentation)

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 Pr$$_{0.6}$$Ca$$_{0.4}$$MnO$$_3$$ around 8 T and the valence transition of YbInCu$$_4$$ around 26 T are shown as a demonstration.

Journal Articles

Magnetic field stabilization by temperature control of an azimuthally varying field cyclotron magnet

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

 Times Cited Count:8 Percentile:57.73(Instruments & Instrumentation)

A magnetic field drift, gradual decrease of the order of 10$$^{-4}$$ 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 $$pm$$ 5$$times$$10$$^{-6}$$ and the beam intensity stability of $$pm$$ 2% have been achieved by this temperature control.

Journal Articles

Application of invasion mathematical model in dosimetry for boron neutron capture therapy for malignant glioma

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.

Journal Articles

First measurement of time-resolved neutron yield on JT-60U using a microfission chamber

Hayashi, Takao; Nishitani, Takeo; Ishikawa, Masao

Review of Scientific Instruments, 75(10), p.3575 - 3577, 2004/10

 Times Cited Count:7 Percentile:58.3(Instruments & Instrumentation)

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 $$^{235}$$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.

Journal Articles

Application of a portable pulsed magnet to synchrotron radiation experiments

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

 Times Cited Count:48 Percentile:13.55(Physics, Condensed Matter)

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.

JAEA Reports

Fast ion loss calculation in the ripple compensation magnetic field by ferritic steel insertion using the FEMAG/OFMC code

Urata, Kazuhiro*; Shinohara, Koji; Suzuki, Masanobu*; Kamata, Isao*

JAERI-Data/Code 2004-007, 45 Pages, 2004/03

JAERI-Data-Code-2004-007.pdf:5.63MB

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.

Journal Articles

Design of the beam transportation line from the linac to the 3-GeV RCS for J-PARC

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 $$<$$$$pm$$ 0.1$$%$$ and transverse emittance $$<$$4$$pi$$ mm$$cdot$$mrad. 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.

Journal Articles

Current point formation and magnetic reconnection process in nonlinearly destabilized double tearing modes

Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki

Physics of Plasmas, 10(9), p.3512 - 3520, 2003/09

 Times Cited Count:8 Percentile:72.24(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Analysis program for magnetic field, inductance of air-core coils; COIL

Yoshida, Kiyoshi; Isono, Takaaki; Sugimoto, Makoto; Okuno, Kiyoshi

JAERI-Data/Code 2003-014, 38 Pages, 2003/08

JAERI-Data-Code-2003-014.pdf:2.71MB

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.

Journal Articles

Design of beam optics in the proton beam transport line from synchrotron to spallation neutron target

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 $$pi$$ 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$$^{-4}$$ and 2x10$$^{-3}$$ 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.

Journal Articles

Development of a magnetic field monitoring system for the JAERI AVF cyclotron

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$$^{-6}$$ 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.

Journal Articles

Nonlocal transport related to dynamics along magnetic field line

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.

Journal Articles

Optimization of negative ion extractor in a JAERI 400 keV H$$^{-}$$ ion source

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

 Times Cited Count:1 Percentile:86.83(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Demagnetization of undulator magnets irradiated high energy electrons

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

 Times Cited Count:37 Percentile:7.41(Instruments & Instrumentation)

no abstracts in English

JAEA Reports

High energy particle transport code NMTC/JAM

Niita, Koji*; Meigo, Shinichiro; Takada, Hiroshi; Ikeda, Yujiro

JAERI-Data/Code 2001-007, 128 Pages, 2001/03

JAERI-Data-Code-2001-007.pdf:5.07MB

no abstracts in English

Journal Articles

Temperature control of a cyclotron magnet for stabilization of the JAERI AVF cyclotron beam

Okumura, Susumu; Arakawa, Kazuo; Fukuda, Mitsuhiro; Nakamura, Yoshiteru; Yokota, Wataru; Ishimoto, Takayuki*; Kurashima, Satoshi; Ishibori, Ikuo; Nara, Takayuki; Agematsu, Takashi; et al.

AIP Conference Proceedings 600, p.330 - 332, 2001/00

Frequent corrections of the magnetic field of the JAERI AVF cyclotron were required for keeping a beam current constant during long time operation. We observed correlation between the magnetic field and the temperature of the cyclotron magnet yoke by measuring the magnetic field with an NMR probe and the temperature with platinum resistance thermometers. The unstable phenomenon of a cyclotron beam was induced by temperature change in the magnet yoke caused mainly by thermal conduction from the main coil. To restrain the thermal conduction to the yoke, we have inserted temperature controlled copper plates between the yoke and the main coil. In addition, a temperature control system of the cooling water of the trim coils has been installed independent of the total cooling system for controlling the pole tip temperature. An optimum condition of the temperature control systems for stabilizing the magnetic field has been investigated.

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