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Journal Articles

Sodium diffusion in hard carbon studied by small- and wide-angle neutron scattering and muon spin relaxation

Oishi, Kazuki*; Igarashi, Daisuke*; Tatara, Ryoichi*; Kawamura, Yukihiko*; Hiroi, Kosuke; Suzuki, Junichi*; Umegaki, Izumi*; Nishimura, Shoichiro*; Koda, Akihiro*; Komaba, Shinichi*; et al.

Journal of Physics; Conference Series, 2462, p.012048_1 - 012048_5, 2023/03

Journal Articles

Optics tuning for beam collimation in the J-PARC 3-50 beam transport line

Harada, Hiroyuki; Meigo, Shinichiro; Shirakata, Masashi*; Sato, Yoichi*; Tamura, Fumihiko; Tejima, Masaki*; Hashimoto, Yoshinori*; Igarashi, Susumu*; Koseki, Tadashi

JPS Conference Proceedings (Internet), 8, p.012010_1 - 012010_6, 2015/09

The J-PARC 3-50BT line is the beam transport line from 3-GeV rapid-cycling synchrotron (RCS) to 50-GeV main ring (MR). The RCS is the high-intensity proton accelerator, where designed beam power is 1 MW, and has the complex source of space charge effect, etc. Therefore, the uncontrolled emittance growth and beam halo increase nonlinearly with the increasing the beam power. Additionally, the physical aperture of MR with 81 $$pi$$ mm mrad is smaller than that of RCS with 486 $$pi$$ mm mrad. Therefore, the 3-50BT line has the collimators in order to remove the tail or halo of the extracted beam from the RCS. The designed collimator aperture is 54 $$pi$$ mm mrad. It is required to measure and optimize the optics parameters in the collimator area for taking full advantage of the beam collimation. Especially, it is very important to make the dispersion functions free in the collimator area and optimize the beta function. This paper will introduce the method of optics measurement and report the result of the measurement and optimization based on the simulation.

Journal Articles

On-site background measurements for the J-PARC E56 experiment; A Search for the sterile neutrino at J-PARC MLF

Ajimura, Shuhei*; Bezerra, T. J. C.*; Chauveau, E.*; Enomoto, T.*; Furuta, Hisataka*; Harada, Masahide; Hasegawa, Shoichi; Hiraiwa, T.*; Igarashi, Yoichi*; Iwai, Eito*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2015(6), p.063C01_1 - 063C01_19, 2015/06

 Times Cited Count:6 Percentile:45.45(Physics, Multidisciplinary)

The J-PARC E56 experiment aims to search for sterile neutrinos at the J-PARC Materials and Life Science Experimental Facility (MLF). In order to examine the feasibility of the experiment, we measured the background rates of different detector candidate sites, which are located at the third floor of the MLF, using a detector consisting of plastic scintillators with a fiducial mass of 500 kg. The gammas and neutrons induced by the beam as well as the backgrounds from the cosmic rays were measured, and the results are described in this article.

Journal Articles

Optics tuning at the J-PARC 3-50BT line

Harada, Hiroyuki; Meigo, Shinichiro; Shirakata, Masashi*; Sato, Yoichi*; Tamura, Fumihiko; Tejima, Masaki*; Hashimoto, Yoshinori*; Igarashi, Susumu*; Koseki, Tadashi

Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.39 - 43, 2014/06

The J-PARC 3-50 BT line is the beam transport line of extracted beam from 3-GeV rapid-cycling synchrotron (RCS) to 50-GeV main ring (MR). The RCS is the high-intensity proton accelerator, which designed beam power is 1 MW, and has the complex source of space charge effect, etc. Therefore, the uncontrolled emittance growth and beam halo increase nonlinearly with the increasing the beam power. Additionally, physical aperture of MR with 81 $$pi$$ mm mrad is smaller than that of RCS with 486 $$pi$$ mm mrad. Therefore, the 3-50 BT line has the collimators in order to scrape the tail/halo of extracted beam from the RCS. The designed collimator aperture is 54 $$pi$$ mm mrad. It is required to measure and optimize the optics parameter in the collimator area for taking full advantage of beam collimation. This paper will introduce the method of optics measurement and report the result of the measurement and optimization based on the simulation.

Journal Articles

Development of the long-pulse ECRF system for JT-60SA

Kobayashi, Takayuki; Isayama, Akihiko; Fasel, D.*; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.

Journal of Plasma and Fusion Research SERIES, Vol.9, p.363 - 368, 2010/08

Improvements are required for expanding the pulse length of the JT-60 ECRF system (5s) for JT-60SA (100s). Newly developed power supplies will be fabricated and installed by EU. The conditioning operation of an improved gyrotron equipping a newly designed mode convertor has been started. The mode convertor will reduce heat flux on the internal components and therefore expected to enable long pulse operation at 1 MW. Pre-programmed and/or feedback control of the heater current and anode voltage, which was successfully demonstrated in JT-60U, will be key techniques because the beam current decreases during a shot. The evacuated transmission lines have a capability of 1 MW per line. Since maintenance of the components in the vacuum vessel is difficult, a linear motion antenna concept was proposed to reduce risks of water leakage and fault of the driving mechanism in the vacuum vessel. The detailed design and the low power test of a mock-up antenna have been started.

Journal Articles

Developments of high power gyrotron and power modulation technique using the JT-60U ECRF system

Kobayashi, Takayuki; Terakado, Masayuki; Sato, Fumiaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Hiranai, Shinichi; Igarashi, Koichi; et al.

Plasma and Fusion Research (Internet), 4, p.037_1 - 037_10, 2009/08

Electron cyclotron (EC) heating and current drive (CD) are key tools to control fusion plasma especially for effective electron heating and for suppression of neoclassical tearing mode (NTM). Recently, developments of a high power gyrotron and a power modulation technique have been successfully achieved on JT-60U ECRF system in order to enhance the system performance. Stable gyrotron oscillation with oscillation power of 1.5 MW for 1 s was demonstrated in 2007, for the first time. Then temperature rise of cavity and collector has been investigated. It has been shown that the longer pulse operation with 1.5 MW by an improved 110 GHz gyrotron is possible. In addition, modulated ECCD in synchronized with NTM rotation has been performed with the oscillation power of 0.8 MW and the frequency around 5 kHz. The synchronizing system has worked very well and it has played an essential role in NTM suppression experiments on JT-60U.

Journal Articles

Development and achievements on the high power ECRF system in JT-60U

Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.

Nuclear Fusion, 49(8), p.085001_1 - 085001_7, 2009/07

 Times Cited Count:20 Percentile:61.88(Physics, Fluids & Plasmas)

In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation $$>$$ 1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.

JAEA Reports

Study on disassembly work of the radio frequency heating system in the amplifier rooms and heating power supply building

Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Igarashi, Koichi; Sato, Fumiaki; Wada, Kenji; et al.

JAEA-Technology 2008-065, 98 Pages, 2008/10

JAEA-Technology-2008-065.pdf:38.83MB

Construction of the JT-60SA (super advanced) is planned as an upgrade of JT-60U as the satellite tokamak in ITER broader approach and as the national centralized tokamak facility program in Japan. The present JT-60U will be disassembled and the JT-60SA will be constructed at the same location in the JT-60 tours hall. The disassembly work will be planned in the period from 2009 to 2011. In this report, disassembly of the radio frequency heating system of JT-60U in the amplifier rooms and heating power supply building is studied on (1) object for disassembly, (2) work plan, (3) estimation of materials amount, (4) procedure.

Journal Articles

Long pulse/high power ECRF system development in JT-60U

Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation $$>$$ 1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.

JAEA Reports

Study on disassembly work of the radio frequency heating system in the JT-60 torus hall

Yokokura, Kenji; Shimono, Mitsugu; Suzuki, Sadaaki; Sawahata, Masayuki; Igarashi, Koichi; Wada, Kenji; Moriyama, Shinichi

JAEA-Technology 2008-058, 103 Pages, 2008/08

JAEA-Technology-2008-058.pdf:33.88MB

This report summarized the studies on the disassemble work of radio frequency heating system in the torus hall as a preparation for the construction of JT-60SA (super advanced) which is the upgrade of the present large tokamak, JT-60U. The studies of the disassembly work were done with emphasis on the safety management because the work requires treatment of contaminated material with tritium and radiated material by neutron, and (1) object for disassemble, (2) work plan, (3) estimation of materials amount, and (4) procedure were summarized.

JAEA Reports

Development of the power modulation technique in JT-60U ECH system

Terakado, Masayuki; Shimono, Mitsugu; Sawahata, Masayuki; Shinozaki, Shinichi; Igarashi, Koichi; Sato, Fumiaki; Wada, Kenji; Seki, Masami; Moriyama, Shinichi

JAEA-Technology 2007-053, 28 Pages, 2007/09

JAEA-Technology-2007-053.pdf:4.3MB

The electron cyclotron heating (ECH) system at 110 GHz are injected to JT-60U plasmas with pulse modulation at dozens to hundreds of Hz in order to measure heat conductivity of the plasma to investigate plasma confinement. The JT-60U ECH system has a unique feature to realize the pulse modulation by controlling the anode voltage of the triode gyrotron without chopping the main acceleration voltage. The typical depth of the modulation is 80 % at the modulation frequency range of 12.2 Hz to 500 Hz. However in the JT-60SA, higher modulation frequency of some kHz will be required to stabilize neoclassical tearing mode (NTM). The modulation techniques have been investigated and the modulation frequency of 3.5 kHz with the modulation depth of 84 % has been achieved. The modulation frequency up to 3 kHz is available in the pulse widths of the practical operation. As a next step, replacement of the parts in the anode voltage divider circuit is planned to achieve higher modulation frequency.

Journal Articles

Local oxidation induced by inhomogeneous stress on blistered Si surface

Igarashi, Shinichi*; Itakura, Akiko*; Kitajima, Masahiro*; Nakano, Shinsuke*; Muto, Shunsuke*; Tanabe, Tetsuo*; Yamamoto, Hiroyuki; Hojo, Kiichi

Japanese Journal of Applied Physics, Part 1, 45(5A), p.4179 - 4182, 2006/05

 Times Cited Count:3 Percentile:12.95(Physics, Applied)

By utilizing surface stress to modify surface reaction potential and increase surface reactivity, a technique for the twodimensional patterning of surface chemical reactions may be realized by surface stress modulation. A blister is a local protrusion on a solid surface induced by gas ion irradiation, and is considered to create local stress on surface layers. Si(100) substrate was irradiated with H$$^{+}$$ (incident energy: 10 keV, fluence: 1$$times$$10$$^{22}$$ ions) at an angle of 30 to the surface normal. Blisters of 1-5 mm in diameter at the base were formed. After the ion irradiation, the substrate was oxidized. Scanning Auger electron microscopy revealed that, compared with the flat surface, the perimeters of the blisters had a higher oxygen intensity whereas the blister tops had a lower oxygen intensity. The stress distribution of the blister was calculated using the finite element method. It was found that the surface layers were stretched laterally at the blisters tops and compressed at theperimeters, relative to the flat surface. There was a clear correspondence between the O distribution and the stress distribution on the surface. Our results indicate that the patterned oxidation of the Si surface can be governed by the application of surface stress.

Journal Articles

Local oxidation induced by inhomogeneous stress on the blistered Si surface

Igarashi, Shinichi*; Itakura, Akiko*; Kitajima, Masahiro*; Nakano, Shinsuke*; Muto, Shunsuke*; Tanabe, Tetsuo*; Yamamoto, Hiroyuki; Hojo, Kiichi

Hyomen Kagaku, 25(9), p.562 - 567, 2004/09

Surface stress can be utilized positively in modifying the surface reaction potential and increasing the surface reactivity. Blister is a local protrusion of solid surface induced by gas ion irradiation, and is considered to create local stress on surface layers. Si(100) substrate was irradiated with 10 keV H$$^{+}$$ (fluence; 1$$times$$10$$^{22}$$ ions/m$$^{2}$$) at an angle of 30$$^{circ}$$ to the surface normal. The blisters of several $$mu$$m in diameter at the bottom were formed. After the ion irradiation, the substrate was oxidized. By means of scanning Auger microscopy, we observed that the rims of the blisters have higher oxygen intensities than the flat surfaces and the tops have lower than the flats. The calculated stress distribution of the blister shows that the surface layers should be stretched laterally at the top of blisters and are compressed at the rim, relative to the flat surfaces. The O distribution clearly consists with the stress distribution of the surface. Our results demonstrate a patterned oxidation of Si surface applying its reactivity depending on the surface stress.

Journal Articles

Observation of iron silicide formation by plan-view transmission electron microscopy

Igarashi, Shinichi*; Haraguchi, Masaharu*; Aihara, Jun; Saito, Takeru*; Yamaguchi, Kenji; Yamamoto, Hiroyuki; Hojo, Kiichi

Journal of Electron Microscopy, 53(3), p.223 - 228, 2004/08

 Times Cited Count:4 Percentile:24.19(Microscopy)

no abstracts in English

Journal Articles

Orientational ordering of iron silicide films on sputter etched Si substrate

Igarashi, Shinichi*; Katsumata, Toshinobu*; Haraguchi, Masaharu*; Saito, Takeru*; Yamaguchi, Kenji; Yamamoto, Hiroyuki; Hojo, Kiichi

Vacuum, 74(3-4), p.619 - 624, 2004/06

 Times Cited Count:6 Percentile:27.86(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Sputter etching of Si substrate to synthesize highly oriented $$beta$$-FeSi$$_{2}$$ films

Igarashi, Shinichi; Katsumata, Toshinobu; Haraguchi, Masaharu; Saito, Takeru; Yamaguchi, Kenji; Yamamoto, Hiroyuki; Hojo, Kiichi

Transactions of the Materials Research Society of Japan, 28(4), p.1153 - 1156, 2003/12

We have evaluated the crystal structure of the $$beta$$-FeSi$$_{2}$$ films formed with various sputter etching of Si substrate. Ne$$^{+}$$ sputter etching of Si (100) substrate was performed with ion energies of 1, 3, and 10 keV. After each etching, the substrate was annealed at a temperature of 1073 K for 30 min. The $$beta$$-FeSi$$_{2}$$ films of 100 nm in thickness were formed at 973 K with the amount of deposited Fe, 30 nm. X-ray diffraction revealed that these films have polycrystalline $$beta$$-FeSi$$_{2}$$ structure but strong preferential orientation aligned as $$beta$$-FeSi$$_{2}$$ (100) // Si (100). Furthermore, the oriented structure of the film was improved by lowering the incident energy of Ne$$^{+}$$.

JAEA Reports

Low-power and long-pulse test of a klystron of the JT-60U LHRF heating system

Shimono, Mitsugu; Seki, Masami; Terakado, Masayuki; Igarashi, Koichi*; Ishii, Kazuhiro*; Takahashi, Masami*; Shinozaki, Shinichi; Hiranai, Shinichi; Sato, Fumiaki*; Anno, Katsuto

JAERI-Tech 2003-075, 29 Pages, 2003/09

JAERI-Tech-2003-075.pdf:4.62MB

no abstracts in English

Journal Articles

In-situ observation of surface blistering in silicon by deuterium and helium ion irradiation

Igarashi, Shinichi; Muto, Shunsuke*; Tanabe, Tetsuo*; Aihara, Jun; Hojo, Kiichi

Surface & Coatings Technology, 158-159, p.421 - 425, 2002/09

no abstracts in English

JAEA Reports

None

Igarashi, Hiroshi; Saito, Shinichi*

PNC TN8600 90-011, 188 Pages, 1990/09

PNC-TN8600-90-011.pdf:8.48MB

no abstracts in English

JAEA Reports

None

Igarashi, Hiroshi; Saito, Shinichi*; Takahashi, Takeshi; Yoshioka, Masahiro

PNC TN8600 90-010, 72 Pages, 1990/09

PNC-TN8600-90-010.pdf:4.58MB

no abstracts in English

42 (Records 1-20 displayed on this page)