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Journal Articles

Measurement of the differential cross sections of the $$Sigma^- p$$ elastic scattering in momentum range 470 to 850 MeV/$$c$$

Miwa, Koji*; Fujita, Manami; Hasegawa, Shoichi; Hosomi, Kenji; Ichikawa, Yudai; Imai, Kenichi*; Nanamura, Takuya; Naruki, Megumi; Sako, Hiroyuki; Sato, Susumu; et al.

Physical Review C, 104(4), p.045204_1 - 045204_20, 2021/10

 Times Cited Count:9 Percentile:88.26(Physics, Nuclear)

Journal Articles

Study of $$Sigma N$$ interaction from the $$Sigma p$$ scattering experiment at J-PARC

Miwa, Koji*; Fujita, Manami; Hasegawa, Shoichi; Hosomi, Kenji; Ichikawa, Masaya; Ichikawa, Yudai; Imai, Kenichi*; Nanamura, Takuya; Naruki, Megumi; Sako, Hiroyuki; et al.

Journal of Physics; Conference Series, 1643, p.012174_1 - 012174_6, 2020/12

 Times Cited Count:2 Percentile:85.05

Journal Articles

Nature of structural instabilities in superconducting Sr$$_3$$Ir$$_4$$Sn$$_{13}$$

Kaneko, Koji; Cheung, Y. W.*; Hu, Y.*; Imai, Masaki*; Tanioku, Yasuaki*; Kanagawa, Hibiki*; Murakawa, Joichi*; Moriyama, Kodai*; Zhang, W.*; Lai, K. T.*; et al.

JPS Conference Proceedings (Internet), 30, p.011032_1 - 011032_6, 2020/03

Journal Articles

Evidence of a structural quantum critical point in (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ from a lattice dynamics study

Cheung, Y. W.*; Hu, Y. J.*; Imai, Masaki*; Tanioku, Yasuaki*; Kanagawa, Hibiki*; Murakawa, Joichi*; Moriyama, Kodai*; Zhang, W.*; Lai, K. T.*; Yoshimura, Kazuyoshi*; et al.

Physical Review B, 98(16), p.161103_1 - 161103_5, 2018/10

 Times Cited Count:19 Percentile:67.65(Materials Science, Multidisciplinary)

Journal Articles

High statistics $$Sigma p$$ scattering experiment using high intensity pion beams at J-PARC

Miwa, Koji*; Hasegawa, Shoichi; Hayakawa, Shuhei; Hosomi, Kenji; Imai, Kenichi; Kondo, Yasuhiro; Naruki, Megumi; Sako, Hiroyuki; Sato, Susumu; Sugimura, Hitoshi; et al.

JPS Conference Proceedings (Internet), 17, p.041002_1 - 041002_6, 2017/07

Journal Articles

Second-order structural transition in (Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$

Cheung, Y. W.*; Hu, Y. J.*; Goh, S. K.*; Kaneko, Koji; Tsutsui, Satoshi; Logg, P. W.*; Grosche, F. M.*; Kanagawa, Hibiki*; Tanioku, Yasuaki*; Imai, Masaki*; et al.

Journal of Physics; Conference Series, 807(3), p.032002_1 - 032002_4, 2017/04

BB2016-0329.pdf:0.86MB

 Times Cited Count:5 Percentile:83.85

Journal Articles

Second-order structural transition in the superconductor La$$_3$$Co$$_4$$Sn$$_{13}$$

Cheung, Y. W.*; Zhang, J. Z.*; Zhu, J. Y.*; Yu, W. C.*; Hu, Y. J.*; Wang, D. G.*; Otomo, Yuka*; Iwasa, Kazuaki*; Kaneko, Koji; Imai, Masaki*; et al.

Physical Review B, 93(24), p.241112_1 - 241112_5, 2016/06

AA2016-0058.pdf:0.95MB

 Times Cited Count:14 Percentile:55.22(Materials Science, Multidisciplinary)

Journal Articles

A Beam position fiber counter with scintillation fibers and multi-pixel photon counter for high intensity beam operation

Honda, Ryotaro*; Miwa, Koji*; Matsumoto, Yuki*; Chiga, Nobuyuki*; Hasegawa, Shoichi; Imai, Kenichi

Nuclear Instruments and Methods in Physics Research A, 787, p.157 - 160, 2015/07

 Times Cited Count:7 Percentile:51.55(Instruments & Instrumentation)

A beam position fiber counter consisting of the scintillation fiber and a multi-pixel photon counter was developed in order to handle a 10 MHz secondary pion beam in the J-PARC E40 experiment. This counter was installed at the entrance of the beam line spectrometer at the K1.8 experimental area in J-PARC and used for the momentum reconstruction. In order to suppress the accidental background and reconstruct the beam momentum, a good timing resolution better than 0.8 ns and a good position resolution better than 200 $$mu$$m were simultaneously required for the counter. These requirements were well achieved by reading the 320 fibers with a diameter of 1 mm, which were arranged in a staggered position, with MPPC fiber by fiber. The signal induced from each MPPC was handled with an Extended Analogue SiPM Integrated ReadOut Chip (EASIROC) developed by Omega/IN2P3 in France. In addition, the timing of the discriminated signals from EASIROC was measured by a FPGA-based multi-hit TDC implemented into Spartan-6. Finally, we obtained the timing resolution of 0.68 ns and the position resolution of 190 $$mu$$m under the 9 MHz beam condition using a pion beam.

Journal Articles

Utilization status at TIARA facility

Haruyama, Yasuyuki; Takizawa, Haruki; Hosono, Masakazu; Mizuhashi, Kiyoshi*; Nakamura, Yoshiteru*; Kaneya, Satoshi*; Asai, Takahiro*; Kawabata, Michiko*; Imai, Koji*

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 177, 2014/03

Cyclotron use in FY 2012, was 2243.5 hours beam time. Among them, the use time of Bio technology and Medical application relationship most, I occupy the time spent for the Quarter of the total. Use offer to the outside utilization was 17%. Use the number of days in Electrostatic Accelerators was 490 days. Among them, Basic technology is accounted for using the percentage of 46%, but the use of irradiation Reactor materials and irradiation of Material for space even more, I accounted for 18 percent utilization rate, respectively, of 15%. Use offer to the outside utilization was 8%.

Journal Articles

Calibration of gafchromic dosimetry films for large-area ion-beam distribution measurement

Ishizaka, Tomohisa; Imai, Koji*; Yuri, Yosuke; Yuyama, Takahiro; Ishibori, Ikuo; Okumura, Susumu

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.594 - 596, 2013/08

no abstracts in English

JAEA Reports

Density of Bunsen reaction solution and viscosity of poly-hydriodic acid

Kubo, Shinji; Yoshino, Koji*; Takemoto, Jumpei*; Kasahara, Seiji; Imai, Yoshiyuki; Onuki, Kaoru

JAEA-Technology 2012-037, 20 Pages, 2013/01

JAEA-Technology-2012-037.pdf:17.29MB

Densities of Bunsen reaction solutions in the iodine-sulfur process were measured with an oscillating U-tube density meter. Two types of the solutions were prepared to simulate sulfuric acid solutions and hydriodic acid solutions of the Bunsen reaction step. The former solution ranged in concentration from 0 to 45 wt% of sulfuric acid containing HI and I$$_{2}$$ of 0-2 mole%; the latter solution contained 0-17 mole% I$$_{2}$$, 1-15 mole% HI and 0-2 mole% H$$_{2}$$SO$$_{4}$$. The temperature of the measured solution were 10-60 $$^{circ}$$C. It was found that, in both solutions, the effect of HI and I$$_{2}$$ concentration on the density could well be represented by using a kind of mole fraction of iodine atom. Based on the finding, a set of correlation equations between the densities and the compositions were derived. Additionally, viscosities of ploy-hydriodic acid were measured using an oscillating viscosity meter in temperature range of 5-40 $$^{circ}$$C, and in the composition range of 0-17 mole% I$$_{2}$$ and 1-15 mole% HI; a empirical equation to calculate viscosity from the composition and the temperature are obtained.

Journal Articles

Use of gafchromic dosimetry films to measure a large-area ion-beam distribution

Ishizaka, Tomohisa; Imai, Koji*; Yuri, Yosuke; Yuyama, Takahiro; Ishibori, Ikuo; Okumura, Susumu

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 157, 2013/01

Journal Articles

Observation of ion cyclotron emission owing to DD fusion product H ions in JT-60U

Sato, Shoichi*; Ichimura, Makoto*; Yamaguchi, Yusuke*; Katano, Makoto*; Imai, Yasutaka*; Murakami, Tatsuya*; Miyake, Yuichiro*; Yokoyama, Takuro*; Moriyama, Shinichi; Kobayashi, Takayuki; et al.

Plasma and Fusion Research (Internet), 5, p.S2067_1 - S2067_4, 2010/12

Ion cyclotron emissions (ICEs) due to deuterium-deuterium fusion-product (FP) ions on JT-60U are studied. ICE due to H-ions is identified from the difference of the toroidal wave number of 2nd ICE(D). The parameter dependence for the appearance of ICE(H) is investigated from the experimental conditions and also is studied by using "Escape Particle Orbit analysis Code (EPOC)".

Journal Articles

Plasma generation at atmospheric pressure using a high-power microwave beam and its application to rocket propulsion

Oda, Yasuhisa*; Komurasaki, Kimiya*; Takahashi, Koji; Kasugai, Atsushi; Imai, Tsuyoshi*; Sakamoto, Keishi

Electrical Engineering in Japan, 161(2), p.1 - 7, 2007/11

 Times Cited Count:1 Percentile:11.91(Engineering, Electrical & Electronic)

Experiments on microwave plasma generation and its application to microwave beamed energy propulsion were conducted using a 1 MW-class, 170 GHz gyrotron. The microwave beam was focused using a parabola reflector and plasma was initiated near the focal point in the ambient air. Plasma propagated upstream in the microwave beam channel while absorbing microwaves. Its propagation velocity was supersonic when the microwave power density was greater than 75 kW/cm$$^{2}$$. The propulsive impulse was measured using a cone-cylinder shaped thruster model. As a result, the maximum momentum coupling coefficient was obtained at a certain plasma propagation distance. In addition, a larger momentum coupling coefficient was obtained when plasma was propagated at a supersonic velocity. This is because supersonic plasma propagation forms a strong shock wave, resulting in an efficient pressure increase.

Journal Articles

Plasma generation at atmospheric pressure using a high power microwave beam and its application to rocket propulsion

Oda, Yasuhisa*; Komurasaki, Kimiya*; Takahashi, Koji; Kasugai, Atsushi; Imai, Tsuyoshi*; Sakamoto, Keishi

Denki Gakkai Rombunshi, A, 126(8), p.807 - 812, 2006/08

Experiments on microwave plasma generation and its application to microwave beamed energy propulsion were conducted using a 1MW-class, 170GHz gyrotron. The microwave beam was focused using a parabola reflector and plasma was initiated near the focal point in the ambient air. Plasma propagated upstream in the microwave beam channel while absorbing microwave. Its propagation velocity was supersonic when the microwave power density was larger than 75kW/cm$$^{2}$$. The propulsive impulse was measured using a cone-cylinder shaped thruster model. As a result, maximum momentum coupling coefficient was obtained at a certain plasma propagation distance. In addition, large momentum coupling coefficient was obtained when plasma was propagated at a supersonic velocity. It would be because supersonic plasma propagation forms a strong shock wave, resulting in an efficient pressure increase.

Journal Articles

Development of reliable diamond window for EC launcher on fusion reactors

Takahashi, Koji; Illy, S.*; Heidinger, R.*; Kasugai, Atsushi; Minami, Ryutaro; Sakamoto, Keishi; Thumm, M.*; Imai, Tsuyoshi

Fusion Engineering and Design, 74(1-4), p.305 - 310, 2005/11

 Times Cited Count:13 Percentile:65.49(Nuclear Science & Technology)

A new diamond window with the copper-coated edge for an EC launcher is developed. The diamond window is designed to cool its disk edge. Since Cu is coated at the entire edge, ingress of cooling water into a transmission line in case of failure on the edge is negligible. In addition, corrosion of Al blaze between the edge and the Inconel cuffs can be avoided. A 170GHz, RF transmission experiment equivalent to a MW-level transmission was carried out to investigate the capability of the edge cooling. The transmission power and pulse are 55kW and 3sec, respectively. Temperature increase was 45$$^{circ}$$C and alomost became constant. Thermal calculation with tan$$delta$$ of 4.4$$times$$10$$^{-4}$$ and thermal conductivity of 1.9kW/m/K agrees with the experiment. Since tan$$delta$$ of the diamond is much higher than the actual one (tan$$delta$$=2$$times$$10$$^{-5}$$), the temperature increase corresponds to that of 1MW transmission. It concludes that the Cu coating dose not degrade the edge cooling capability and improves the reliability of the diamond window.

Journal Articles

Thermal analysis and Ohmic loss estimation of polarizer for ITER ECCD system

Saigusa, Mikio*; Takahashi, Koji; Kashiwa, Yoshinori*; Oishi, Shimpei*; Hoshi, Yuki*; Nakahata, Hiroyuki*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi*

Fusion Engineering and Design, 74(1-4), p.473 - 478, 2005/11

 Times Cited Count:4 Percentile:30.57(Nuclear Science & Technology)

The specification of an electron cyclotron current driving (ECCD) system in International Thermonuclear Experimental Reactor (ITER) demands severe operational conditions for transmission lines and polarizers. For evaluating Ohmic loss of a miter bend type polarizer, the six polarizers were made of chromium copper alloy, installed in miter bends and tested at a frequency of 170GHz, rf power of 441kW and pulse duration of 0.1-6 seconds. The increase in temperature on the back of the grooved mirrors has been measured with thermo couplers during high power rf pulses. The Ohmic loss of grooved mirrors strongly depends on the rotation angle of the polarization plane of the incident waves and the mirror rotation in high power experiments, for example the Ohmic loss distributed from 0.2% to1.6%. The thermal analysis of grooved mirror has been performed with the 3D FEM code: FEVA. The all strange behavior of Ohmic loss of polarizers could be explained, theoretically.

Journal Articles

Gamow-Teller decay of the $$T=1$$ nucleus $$^{46}$$Cr

Onishi, Takeo*; Gelberg, A.*; Sakurai, Hiroyoshi*; Yoneda, Kenichiro*; Aoi, Nori*; Imai, Nobuaki*; Baba, Hidetada*; Von Brentano, P.*; Fukuda, Naoki*; Ichikawa, Yuichi*; et al.

Physical Review C, 72(2), p.024308_1 - 024308_7, 2005/08

 Times Cited Count:21 Percentile:77.68(Physics, Nuclear)

no abstracts in English

Journal Articles

Thermal desorption behavior of deuterium implanted into polycrystalline diamond

Kimura, Hiromi*; Sasaki, Masayoshi*; Morimoto, Yasutomi*; Takeda, Tsuyoshi*; Kodama, Hiroshi*; Yoshikawa, Akira*; Oyaizu, Makoto*; Takahashi, Koji; Sakamoto, Keishi; Imai, Tsuyoshi; et al.

Journal of Nuclear Materials, 337-339, p.614 - 618, 2005/03

 Times Cited Count:7 Percentile:45(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Design performance of front steering-type electron cyclotron launcher for ITER

Takahashi, Koji; Imai, Tsuyoshi; Kobayashi, Noriyuki*; Sakamoto, Keishi; Kasugai, Atsushi; Hayakawa, Atsuro*; Mori, Seiji*; Mori, Kensuke*

Fusion Science and Technology, 47(1), p.1 - 15, 2005/01

An applicability of a front steering type EC launcher to a fusion reactor is described with the design and thermal, electromagnetic and nuclear analysis using the ITER design conditions. Maximum stress of the support keys of the front shield module, the welds of the keys and the mirror shaft induced by electromagnetic force are 85.5MPa and 34.1MPa and 22MPa, respectively, which are less than 1.5Sm of stainless steel(205MPa). Maximum thermal stress in the front shield module and the mirror, which are 249MPa and 350MPa, respectively, are obtained at the inner surface of a stainless steel cooling tube. The stresses are less 3Sm of stainless steel at 200$$^{circ}$$C(410MPa). The annual neutron fluence and the dose rate at the vacuum window(closure plate) are estimated to be 10$$^{13}$$$$sim$$10$$^{12}$$ n/cm$$^{2}$$/yr and 45$$mu$$Sv/h, respectively that satisfy the shield criteria of the ITER. It appears that the design of the front steering type EC launcher is applicable to an ITER grade reactor.

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