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ABSTRACT: 10-nm-thick γ<sup>′</sup> -Fe <sub>4</sub> N films were grown epitaxially on LaAlO <sub>3</sub>(001) and MgO(001) substrates by molecular beam epitaxy using solid Fe and a radio-frequency NH <sub>3</sub> plasma. The lattice mismatch of these substrates to γ<sup>′</sup> -Fe <sub>4</sub> N is 0% and 11%, respectively. Spin and orbital magnetic moments of these γ<sup>′</sup> -Fe <sub>4</sub> N epitaxial films were deduced by x-ray magnetic circular dichroism measurements at 300 K. The total magnetic moments are almost the same for the two substrates, that is, 2.44±0.06 μ<sub> B </sub> and 2.47±0.06 μ<sub> B </sub> , respectively. These values are very close to those predicted theoretically, and distinctively larger than that for α -Fe .
Applied Physics Letters 04/2011; · 3.84 Impact Factor
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K.H. Tanaka,
E. Hirose,
H. Takahashi,
K. Agari,
M. Ieiri,
Y. Katoh,
A. Kiyomichi,
M. Minakawa,
R. Muto,
M. Naruki, [......],
H. Watanabe,
Y. Yamanoi,
M. Iio,
K. Kato,
T. Ozawa,
M. Saijyo, Y. Saitoh,
H. Satoh,
K. Yahata,
T. Birumachi
[show abstract]
[hide abstract]
ABSTRACT: More than 50 radiation-resistant electromagnets were constructed for the primary proton and the secondary particle beam lines of the Hadron Experimental Hall of Japan Proton Accelerator Research Complex (J-PARC). The main radiation-resistant technologies we employed were the Polyimide-resin Insulation conductor for magnets at the relatively low radiation exposure and the Mineral Insulation Cable for magnets at the seriously high radiation environment. The remote handling and maintenance scheme of radiation-resistant magnets for seriously high radiation environment was developed also based on the Chimney magnet technology and applied to magnets near the production target in the Hadron Hall. On January 27th 2009, the first proton beam was successfully introduced to the Hadron Hall from the main accelerator of J-PARC, i.e. 50 GeV Proton Synchrotron. On February 10th, the secondary particles were extracted to the experimental area of the Hadron Hall through the secondary particle beam line. No serious problem happened on magnets of both primary proton and the secondary particle beam lines until the end of the beam operation scheduled on February 26th .
IEEE Transactions on Appiled Superconductivity 07/2010; · 1.04 Impact Factor
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H. Takahashi,
K. Agari,
E. Hirose,
M. Ieiri,
M. Iio,
Y. Katoh,
A. Kiyomichi,
M. Minakawa,
R. Muto,
M. Naruki, [......],
M. Takasaki,
K.H. Tanaka,
A. Toyoda,
H. Watanabe,
Y. Yamanoi,
K. Ogata,
M. Saijyo, Y. Saitoh,
K. Katoh,
K. Yahata
[show abstract]
[hide abstract]
ABSTRACT: The target station in the hadron experimental facility at J-PARC consists of a production target and a huge vacuum chamber in which several secondary-beam-line magnets can work. This vacuum chamber system aims to remove the vacuum beam pipe from the magnet gap, because the cooling of the beam pipe is the most serious problem in the high intensity beam facility. We have developed indirectly cooled radiation-resistant magnets for the hadron target station. Their coils are made of solid-conductor type mineral-insulation cables and stainless-steel water pipes. They have the great advantages that electric circuits can be completely independent of water pass. The mechanical strength and the insulation performance of the coil are significantly improved also because the insulation water pipes can be avoided from the water pass. A C-type sector dipole and a figure-8-type quadrupole magnet have been fabricated by using indirectly cooled radiation-resistant magnet technology, and installed in the vacuum chamber. We have succeeded to operate them in vacuum stably with the current of DC 1000 A by improving the end structure of the MIC coils and increasing their emissivity. These magnets have been used for the real beam operation without any serious problems.
IEEE Transactions on Appiled Superconductivity 07/2010; · 1.04 Impact Factor
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Review of Scientific Instruments 04/2010; · 1.37 Impact Factor
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T. Kataoka,
M. Kobayashi,
Y. Sakamoto,
G. S. Song,
A. Fujimori,
F.-H. Chang,
H.-J. Lin,
D. J. Huang,
C. T. Chen,
T. Ohkochi,
Y. Takeda,
T. Okane, Y. Saitoh,
H. Yamagami,
A. Tanaka,
S. K. Mandal,
T. K. Nath,
D. Karmakar,
I. Dasgupta
[show abstract]
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ABSTRACT: We have studied the electronic structure of Fe-doped ZnO nanoparticles, which have been reported to show ferromagnetism at room temperature, by x-ray photoemission spectroscopy, resonant photoemission spectroscopy, x-ray absorption spectroscopy, and x-ray magnetic circular dichroism (XMCD). From the experimental and cluster-model calculation results, we find that Fe atoms are predominantly in the Fe <sup>3+</sup> ionic state with mixture of a small amount of Fe <sup>2+</sup> and that Fe <sup>3+</sup> ions are dominant in the surface region of the nanoparticles. It is shown that the room temperature ferromagnetism in the Fe-doped ZnO nanoparticles primarily originated from the antiferromagnetic coupling between unequal amounts of Fe <sup>3+</sup> ions occupying two sets of nonequivalent positions in the region of the XMCD probing depth of ∼2–3 nm .
Journal of Applied Physics 03/2010; · 2.17 Impact Factor
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ABSTRACT: A solid-electrolyte switch (ldquoNanoBridgerdquo) has been successfully embedded into a 0.13-mum-node dual-damascene Cu interconnect using a highly reliable bilayer solid-electrolyte (TaSiO/Ta<sub>2</sub>O<sub>5</sub>) and a thin oxidation barrier, resulting in an excellent ON/OFF ratio (> 10<sup>9</sup>) at a low ON resistance of 50Omega. The newly developed bilayer solid-electrolyte has improved the thermal stability during the BEOL process as well as improved electrical breakdown. The CMOS compatible NanoBridge is a promising switch to achieve high-performance and low-cost programmable LSIs.
VLSI Technology, 2009 Symposium on; 07/2009
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M. Kobayashi,
G. S. Song,
T. Kataoka,
Y. Sakamoto,
A. Fujimori,
T. Ohkochi,
Y. Takeda,
T. Okane, Y. Saitoh,
H. Yamagami,
H. Yamahara,
H. Saeki,
T. Kawai,
H. Tabata
[show abstract]
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ABSTRACT: The electronic structure of the oxide semiconductor ZnO has been investigated using soft x-ray angle-resolved photoemission spectroscopy (ARPES). The obtained band dispersions within the k<sub>x</sub>-k<sub>y</sub> planes reflect the symmetry of the Brillouin zone and show no surface-state-derived flat bands. Band dispersions along the k<sub>z</sub> direction have also been observed. The obtained band dispersions qualitatively agree with band-structure calculations except for the bandwidth. The observations provide experimental evidence that soft x-ray ARPES enables us to study the bulk band structure of semiconductors.
Journal of Applied Physics 07/2009; · 2.17 Impact Factor
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ABSTRACT: In recent years, there has been increasing demand to miniaturize wiring harness connectors in automobiles due to the increasing volume of electronic equipment and the reduction of the installation space allocated for the electronic equipment in automobiles for the comfort of the passengers. With this demand, contact failure caused by the fretting corrosion seems to become a serious problem in the future. There are many reports about fretting contact resistance transitions from the low contact resistance level to the high contact resistance level, but there are few reports about observation of the microstructure transition. In our previous study, we conducted observation using SEM, TEM and micro hardness measurement using a nanoindentation tester on low and high contact resistance samples (dimple-flat configuration) under the fixed test conditions (contact load: IN, tin plating thickness:5 mum). In this report, we examined microstructure observation of flat fretting contacts, modifying the tin plating thickness as a parameter. Based on the observation results, we considered the change of the contact microstructure and the difference of the contact resistance rising curve behavior caused by the tin plating thickness.
Electrical Contacts, 2008. Proceedings of the 54th IEEE Holm Conference on; 11/2008
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M. Kobayashi,
Y. Ooki,
M. Takizawa,
G. S. Song,
A. Fujimori,
Y. Takeda,
K. Terai,
T. Okane,
S.-I. Fujimori, Y. Saitoh,
H. Yamagami,
M. Seki,
T. Kawai,
H. Tabata
[show abstract]
[hide abstract]
ABSTRACT: By means of photoemission and x-ray absorption spectroscopy, we have studied the electronic structure of ( Ni , Zn , Fe , Ti )<sub>3</sub> O <sub>4</sub> thin films, which exhibits a cluster glass behavior with a spin-freezing temperature T<sub>f</sub> of ∼230 K and photoinduced magnetization (PIM) below T<sub>f</sub> . The Ni and Zn ions were found to be in the divalent states. Most of the Fe and Ti ions in the thin films were trivalent ( Fe <sup>3+</sup>) and tetravalent ( Ti <sup>4+</sup>) , respectively. While Ti doping did not affect the valence states of the Ni and Zn ions, a small amount of Fe <sup>2+</sup> ions increased with Ti concentration, consistent with the proposed charge-transfer mechanism of PIM.
Applied Physics Letters 03/2008; · 3.84 Impact Factor
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ABSTRACT: The heating characteristics of an RF rectangular cavity applicator for hyperthermic treatment that targets deep-seated tumors were investigated numerically and experimentally. In the numerical study, Maxwell's equations and heat transfer equations were solved for a dielectric phantom with and without blood flow. Conductive caps attached to the dielectric phantom to shield the non-tumor regions. The experimental study showed the validity and possibility of heating deep-seated tumors. Thus, the rectangular resonant cavity applicator with an L-type antenna can heat deep-seated tumors.
Engineering in Medicine and Biology Society, 2007. EMBS 2007. 29th Annual International Conference of the IEEE; 09/2007
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H. Takahashi,
K. Agari,
E. Hirose,
M. Ieiri,
Y. Katoh,
M. Minakawa,
H. Noumi,
Y. Sato,
Y. Suzuki,
M. Takasaki,
K.H. Tanaka,
A. Toyoda,
H. Watanabe,
Y. Yamada,
Y. Yamanoi,
M. Saijo, Y. Saitoh,
K. Katoh,
K. Yahata
[show abstract]
[hide abstract]
ABSTRACT: In a high-intensity proton beam facility, beam line elements downstream of a production target are exposed to a huge amount of radiation and heat. A water-cooled beam collimator must be located between the target and the magnets, and the iron yokes of the magnets also have to be cooled by water. Moreover, beam pipes are closer to the beam than the magnet poles and more difficult to cool sufficiently without tritium production. Therefore, the magnets are placed in a large vacuum chamber, instead of using vacuum pipes located within the pole gaps. In order to reduce the residual radiation dose during maintenance, the chamber lid and feedthroughs are 4 meter above the beam line, and radiation-shielding blocks are also stacked in the chamber. We have tested magnet operation in vacuum using a dipole magnet with mineral-insulation-cable (MIC) coils and a nickel-coated yoke. A magnet with 2500-A-class hollow-conductor MIC coils has worked successfully with the current of DC 3000 A. The stability of operation in vacuum was confirmed by measuring the temperature with thermocouples and the magnetic field with a NMR probe. We have also succeeded in operating a 1000-A-class solid-conductor MIC coil in vacuum
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
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[show abstract]
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ABSTRACT: Electromagnetic and heat-transfer equations were solved to investigate a radio frequency (RF) rectangular resonant cavity applicator. The possibility of heating a deep-seated tumor was demonstrated. A torso-shaped dielectric phantom was made. It has electrical constants resembling those of human muscle. Several L-type antennas were made and placed at appropriate locations to heat a deep region. Measured results agreed with the calculated results. Results show that the rectangular resonant cavity applicator with the L-type antennas can heat deep-seated tumors
Engineering in Medicine and Biology Society, 2005. IEEE-EMBS 2005. 27th Annual International Conference of the; 02/2006
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[show abstract]
[hide abstract]
ABSTRACT: An extremely compact, all-permanent-magnet electron cyclotron resonance ion source was designed and manufactured mainly for materials development. The ion source was installed in a 400 kV ion implanter, and a heavy ion beam in the mega-electron-volt (MeV) energy region with high beam intensity was available using multiply charged ions from the ion source. The magnet measured 120 mm in length and 30 mm and 110 mm in inner and outer diameters, respectively. A high magnetic field in the plasma chamber was formed by the unique permanent magnet structure. The maximum and minimum mirror fields achieved were 0.62 and 0.40 T, respectively. Up to 10 W of 13 GHz microwave power was fed to the source by the solid-state microwave generator, and the minimum B structure was formed in the plasma chamber. In the preliminary result at the test stand, an O5+ beam of 11 eμA, an Ar4+ beam of 80 eμA, and a He2+ beam of 100 eμA were available and an Ar12+ beam of 10 eμA was obtained with microwave power of only 10 W. The beam performance of the new source and the previous 10 GHz source developed at TIARA were compared. © 2004 American Institute of Physics.
Review of Scientific Instruments 05/2004; 75(5):1502-1505. · 1.37 Impact Factor
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[show abstract]
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ABSTRACT: An 18 GHz electron cyclotron resonance ion source under development since. 1994 has a solenoid coil between a pair of mirror coils to vary the mirror ratio over a wide range. The solenoid coil of the original design formed a small bump in the bottom of the mirror field profile when the source parameters were optimized for high charge states. Source performance in generating highly charged ions improved with a number of minor changes on the vacuum, the gas feed, and the beam extraction system. The maximum beam current of Ar16+ was 2 enA, which was much lower than that expected from the microwave frequency and the magnetic field strength. Little effect of a biased disk on intensities of highly charged ions and dependence of the charge state distribution on the solenoid coil current suggested that the bump divided plasma into two regions and limited the source performance. The bump was removed by halving the solenoid coil length, and the beam current of Ar16+ increased to 1.3 eμA as a result. © 2000 American Institute of Physics.
Review of Scientific Instruments 01/2000; 71(2):906-908. · 1.37 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We have proposed a muscle fatigue evaluation method based on the
relationship between a superimposed M wave (SM wave) and the preceding
background activity. In this paper, we described the application of our
method in field assessment based on the results at different contraction
levels. At different levels of submaximum voluntary sustained
contractions, we estimated the correlation between instantaneous
frequency (Ifs) of the SM wave and mean power frequency (MPF) of the
preceding background activity. The results showed that the MPF and Ifs
were uncorrelated or sometimes showed negative correlation during the
low level contractions. Hence, the 30% of maximum voluntary contraction
was employed for the assessment of muscle fatigue before and after
running exercise. Results of the first day showed the same results of
the low level contractions, but they showed the features of muscle
fatigue like those at the high level contractions on third day
BMES/EMBS Conference, 1999. Proceedings of the First Joint; 02/1999
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K. Sato,
T. Uchiyama,
H. Majima,
M. Nakajima,
M. Inoue,
J. Yamanaka, Y. Saitoh,
S. Miyahara,
M. Kamiy,
H. Ikeda,
M. Tanaka,
T. Matsuda,
Y. Yamada
[show abstract]
[hide abstract]
ABSTRACT: An optical link system (OLS) is to be used in the data acquisition
(DAQ) system for the Silicon Vertex Detector of the KEK B-factory
experiment (BELLE collaboration). In this study we report the 10-bit, or
channel (ch), OLS in which CMOS ICs are used as the transceiver
circuitry for both transmitting and receiving, infrared LEDs are used as
photo transmitting devices, and Si PIN photodiodes (PDs) are used as
photo-receiving devices. We have obtained a 32 Mbps/ch data rate, at
around 5 dB of dynamic range, with less than 8 nsec of jitters and an
error rate of less than 10<sup>-9</sup>. The scheme we proposed in this
study has been confirmed assuming it will be used in the readout system
IEEE Transactions on Nuclear Science 07/1998; · 1.45 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: A new technique has been developed to introduce very refractory materials into an electron cyclotron resonance ion source by fluorinating them with SF6 plasma, and we succeeded in generating multiply charged ions of B, Mo, Nb, W, and Ta. A metallic sample is set inside the plasma chamber with SF6 plasma, in which the metallic fluoride is generated with sufficiently high vapor pressure by a chemical reaction between fluorine and the metal. The gaseous metallic fluoride is decomposed into fluorine and metal, which are ionized by the SF6 plasma. Generally, ion sources are corroded by gases of fluorine and fluoride, but utilization of SF6 gas reduces the corrosion and allows stable operation for a long time. © 1998 American Institute of Physics.
Review of Scientific Instruments 01/1998; 69(2):703-705. · 1.37 Impact Factor
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Y. Saitoh,
T. Akamine,
M. Inoue,
J. Yamanaka,
N. Echigo,
S. Miyahara,
M. Kamiya,
H. Ikeda,
T. Matsuda,
A. Bozek, [......],
Y. Asano,
S. Mori,
Y. Tsujita,
H. Miyata,
K. Miyano,
M. Hazumi,
T. Hara,
T. Kawasaki,
Y. Nagashima,
K. Senyo
[show abstract]
[hide abstract]
ABSTRACT: The previous double-sided silicon microstrip detector (DSSDs)
prototype with integrated coupling capacitors formed by
oxide-nitride-oxide (ONO) dielectric film showed band-to-band tunneling
(BET) current at the field-plate structure for the N<sup>+</sup> strip,
which represented a limitation of the biasing configuration. We report
improved characteristics of the modified field-plate structure and the
wide-pitch n-side readout using a multi p-stop structure combined
thereon
IEEE Transactions on Nuclear Science 07/1997; · 1.45 Impact Factor
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H. Ikeda,
M. Tanaka,
T. Matsuda,
C. Fukunaga,
T. Nobori, Y. Saitoh,
T. Akamine,
M. Inoue,
J. Yamanaka,
M. Mandai,
H. Takeuchi,
T. Kitta,
M. Saitoh,
S. Miyahara,
M. Kamiya
[show abstract]
[hide abstract]
ABSTRACT: The data-acquisition system for a silicon micro-vertex detector of
the BELLE experiment is described with special emphasis placed on the
front-end circuits and their interfaces. The description includes a
128-channel preamplifier chip, a silicon-based double-sided hybrid card,
and readout control chips for digital interfaces, which are discussed in
terms of both architectural and operational aspects
IEEE Transactions on Nuclear Science 07/1997; · 1.45 Impact Factor
