Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 82

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Characterization of the PTW 34031 ionization chamber (PMI) at RCNP with high energy neutrons ranging from 100 - 392 MeV

Theis, C.*; Carbonez, P.*; Feldbaumer, E.*; Forkel-Wirth, D.*; Jaegerhofer, L.*; Pangallo, M.*; Perrin, D.*; Urscheler, C.*; Roesler, S.*; Vincke, H.*; et al.

EPJ Web of Conferences (Internet), 153, p.08018_1 - 08018_5, 2017/09

 Times Cited Count:0 Percentile:100

At CERN, gas-filled ionization chambers PTW-34031 (PMI) are commonly used in radiation fields including neutrons, protons and $$gamma$$-rays. A response function for each particle is calculated by the radiation transport code FLUKA. To validate a response function to high energy neutrons, benchmark experiments with quasi mono-energetic neutrons have been carried out at RCNP, Osaka University. For neutron irradiation with energies below 200 MeV, very good agreement was found comparing the FLUKA simulations and the measurements. In addition it was found that at proton energies of 250 and 392 MeV, results calculated with neutron sources underestimate the experimental data due to a non-negligible gamma component originating from the target $$^{7}$$Li(p,n)Be reaction.

Journal Articles

Shielding experiments of concrete and iron for the 244 MeV and 387 MeV quasi-mono energetic neutrons using a Bonner sphere spectrometer (at RCNP, Osaka Univ.)

Matsumoto, Tetsuro*; Masuda, Akihiko*; Nishiyama, Jun*; Iwase, Hiroshi*; Iwamoto, Yosuke; Satoh, Daiki; Hagiwara, Masayuki*; Yashima, Hiroshi*; Yashima, Hiroshi*; Shima, Tatsushi*; et al.

EPJ Web of Conferences (Internet), 153, p.08016_1 - 08016_3, 2017/09

 Times Cited Count:0 Percentile:100

Neutron energy spectra behind concrete and iron shields were measured for quasi-monoenergetic neutrons above 200 MeV using a Bonner sphere spectrometer (BSS). Quasi-monoenergetic neutrons were produced by the $$^{7}$$Li(p,xn) reaction with 246-MeV and 389-MeV protons. The response function of BSS was also measured at neutron energies from 100 MeV to 387 MeV. In data analysis, the measured response function was used and the multiple neutron scattering effect between the BSS and the shielding material was considered. The neutron energy spectra behind the concrete and iron shields were obtained by the unfolding method using the MAXED code. Ambient dose equivalents were obtained as a function of a shield thickness successfully. For the case of the 244 MeV neutron incidence, the multiple neutron scattering effect on the effective dose is large under 50 cm thickness of the concrete shield.

Journal Articles

Applicability of the two-angle differential method to response measurement of neutron-sensitive devices at the RCNP high-energy neutron facility

Masuda, Akihiko*; Matsumoto, Tetsuro*; Iwamoto, Yosuke; Hagiwara, Masayuki*; Satoh, Daiki; Sato, Tatsuhiko; Iwase, Hiroshi*; Yashima, Hiroshi*; Nakane, Yoshihiro; Nishiyama, Jun*; et al.

Nuclear Instruments and Methods in Physics Research A, 849, p.94 - 101, 2017/03

 Times Cited Count:0 Percentile:100(Instruments & Instrumentation)

Quasi-monoenergetic high-energy neutron fields induced by $$^{7}$$Li(p,n) reactions are used for the response evaluation of neutron-sensitive devices. The quasi-monoenergetic high-energy field consists of high-energy monoenergetic peak neutrons and unwanted continuum neutrons down to the low-energy region. A two-angle differential method has been developed to compensate for the effect of the continuum neutrons in the response measurements. In this study, the two-angle differential method was demonstrated for Bonner sphere detectors, which are typical examples of moderator-based neutron-sensitive detectors, to investigate the method's applicability and its dependence on detector characteristics. Through this study, the adequacy of the two-angle differential method was experimentally verified, and practical suggestions were made pertaining to this method.

Journal Articles

Nitric oxide-mediated bystander signal transduction induced by heavy-ion microbeam irradiation

Tomita, Masanori*; Matsumoto, Hideki*; Funayama, Tomoo; Yokota, Yuichiro; Otsuka, Kensuke*; Maeda, Munetoshi*; Kobayashi, Yasuhiko

Life Sciences in Space Research, 6, p.36 - 43, 2015/07

A radiation-induced bystander response is generally known as a cellular response induced in unirradiated cell by receiving bystander signaling factors released from directly irradiated cells of a cell population. Bystander responses induced by high-LET heavy ions at low fluence are an important problem concerning the health of astronauts in the space environment. Here we set out NO-mediated bystander signal transductions induced by high-LET heavy-ion microbeam irradiation in normal human fibroblasts. Our findings suggest that Akt- and NF-$$kappa$$B-dependent signaling pathway involving COX-2 plays an important role in the NO-mediated high-LET heavy-ion-induced bystander responses. Additionally, COX-2 may be used as a molecular marker of high-LET heavy-ion-induced bystander cells, which are distinguish form directly irradiated cells.

Journal Articles

Mechanisms for the induction of radioadaptive response by radiation-induced bystander response

Matsumoto, Hideki*; Tomita, Masanori*; Otsuka, Kensuke*; Hatashita, Masanori*; Maeda, Munetoshi*; Funayama, Tomoo; Yokota, Yuichiro; Suzuki, Michiyo; Sakashita, Tetsuya; Ikeda, Hiroko; et al.

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 76, 2015/03

The objective of this project is to elucidate molecular mechanisms for the induction of radioadaptive response through radiation-induced bystander responses induced by irradiation with heavy ion microbeams in JAEA. We found that the adaptive response was induced by Ar (520 MeV $$^{40}$$Ar$$^{14+}$$) microbeam-irradiation of a limited number of cells, followed by the broad beam-irradiation and that the adaptive response was almost completely suppressed by the addition of carboxy-PTIO, as a nitric oxide (NO) scavenger. In addition, we found several genes induced specifically and preferentially when radioadaptive response could be induced. We confirmed that ${it iNOS}$ expression was specifically induced only when radioadaptive response could be induced. Our findings strongly suggested that radioadaptive response can be induced by NO-mediated bystander responses evoked by irradiation with heavy ion microbeams.

Journal Articles

Analysis of bystander response in 3D cultured tissue induced by heavy-ion microbeam irradiation

Tomita, Masanori*; Matsumoto, Hideki*; Otsuka, Kensuke*; Funayama, Tomoo; Yokota, Yuichiro; Suzuki, Michiyo; Sakashita, Tetsuya; Kobayashi, Yasuhiko

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 77, 2015/03

Radiation-induced bystander responses are defined as responses in cells that have not been directly targeted by radiation but are in the neighborhood of cells that have been directly exposed. In this study, we aim to clarify a role of bystander response to sustain the homeostasis of damaged tissue using heavy-ion microbeams. We established the heavy-ion microbeam irradiation method to a 3D cultured human epidermis. Using this method, a viable cell rate of the 3D cultured human epidermis irradiated with 260 MeV $$^{20}$$Ne-ion microbeams or broadbeams was analyzed by the MTT method.

Journal Articles

Measurement of neutron energy spectra behind shields for quasi-monoenergetic neutrons generated by 246-MeV and 389-MeV protons using a Bonner sphere spectrometer

Matsumoto, Tetsuro*; Masuda, Akihiko*; Nishiyama, Jun*; Harano, Hideki*; Iwase, Hiroshi*; Iwamoto, Yosuke; Hagiwara, Masayuki*; Satoh, Daiki; Yashima, Hiroshi*; Nakane, Yoshihiro; et al.

Progress in Nuclear Science and Technology (Internet), 4, p.332 - 336, 2014/04

Recently, many high-energy accelerators are used for various fields. Shielding data for high-energy neutrons are therefore very important from the point of view of radiation protection in high energy accelerator facilities. However, the shielding experimental data for high energy neutrons above 100 MeV are very poor both in quality and in quantity. In this study, neutron penetration spectral fluence and ambient dose through iron and concrete shields were measured with a Bonner sphere spectrometer (BSS). Quasi-monoenergetic neutrons were produced by the $$^{7}$$Li(p,xn) reaction by bombarding a 1-cm thick Li target with 246-MeV and 389-MeV protons in the Research Center for Nuclear Physics (RCNP) of the Osaka University. Shielding materials are iron blocks with a thickness from 10 cm to 100 cm and concrete blocks with a thickness from 25 cm to 300 cm.

Journal Articles

Revisit to terahertz wave emission with motions of Josephson vortices

Matsumoto, Hideki*; Koyama, Tomio*; Machida, Masahiko; Ota, Yukihiro*; Yamada, Susumu

Physica C, 491, p.40 - 43, 2013/08

 Times Cited Count:2 Percentile:86.27(Physics, Applied)

no abstracts in English

Journal Articles

Numerical study for electromagnetic wave emission from intrinsic Josephson junction stacks with a dielectric cover

Koyama, Tomio*; Matsumoto, Hideki*; Ota, Yukihiro*; Machida, Masahiko

Physica C, 491, p.20 - 23, 2013/08

 Times Cited Count:0 Percentile:100(Physics, Applied)

no abstracts in English

Journal Articles

Electromagnetic wave emission from intrinsic Josephson junction stacks; A Review of theory and simulation

Machida, Masahiko; Ota, Yukihiro*; Koyama, Tomio*; Matsumoto, Hideki*

Journal of Physics; Conference Series, 393, p.012013_1 - 012013_8, 2012/09

 Times Cited Count:1 Percentile:50.63

Since the discovery of intrinsic Josephson effects in High-Tc cuprate superconductors, a tremendous number of theoretical and experimental studies have been made to clarify the coupling nature between stacked junctions. The reason comes from an expectation that Josephson junctions stacked in atomic-scale synchronize and high-power electromagnetic wave radiates. Consequently, two types of couplings, called "inductive and capacitive couplings" have been so far established. On the basis of the inductive coupling, several papers suggested that THz high-power emission is possible by using Josephson vortex flow states in the presence of layer parallel magnetic field and c-axis transport current. However, there has been no clear evidence of the emission in vortex flow states, although a few works found out only the sign. Afterwards, Ozyuzer et al., reported that they successfully observe a clear emission from intrinsic Josephson junctions. The situation was rather an unexpected one, since the magnetic field is not applied and the employed size is much larger than the experimental trends at that time. In this presentation, we review a history of the quest of the high power electromagnetic wave emission from intrinsic Josephson stacks before and after the Ozyuzer's work from a theoretical and numerical view. Especially, we would like to emphasize that direct numerical simulation techniques on multi-scale dynamical problems between inside and outside the junction have fully developed by authors.

Journal Articles

Response measurement of a Bonner sphere spectrometer for high-energy neutrons

Masuda, Akihiko*; Matsumoto, Tetsuro*; Harano, Hideki*; Nishiyama, Jun*; Iwamoto, Yosuke; Hagiwara, Masayuki*; Satoh, Daiki; Iwase, Hiroshi*; Yashima, Hiroshi*; Nakamura, Takashi*; et al.

IEEE Transactions on Nuclear Science, 59(1), p.161 - 166, 2012/02

 Times Cited Count:11 Percentile:26.17(Engineering, Electrical & Electronic)

In this study, responses of Bonner sphere spectrometer (BSS) for 245 and 388 MeV neutrons was measured at RCNP, Osaka University. The neutrons are generated in the $$^{7}$$Li(p,n) reaction and its spectra consist of a high-energy peak and a continuum down to the low energy. Therefore, the observed counts of BSS caused by the continuum need to be subtracted. Adjusting a Li target angle and a collimator position, 0 deg and 30 deg component of generated neutron are available. While the 0 deg component contains both the peak and the continuum, the 30 deg component is considered to contain only the continuum. Therefore, the response of the peak is obtained. The spectra were measured using the time-of-flight (TOF) method with a NE213 scintillator.

Journal Articles

Establishment of neutron fluence monitoring techniques for quasi-monoenergetic neutron calibration fields of high energy at TIARA

Shikaze, Yoshiaki; Tanimura, Yoshihiko; Saegusa, Jun; Tsutsumi, Masahiro; Uchida, Yoshiaki*; Yoshizawa, Michio; Harano, Hideki*; Matsumoto, Tetsuro*; Mizuhashi, Kiyoshi

JAEA-Review 2010-065, JAEA Takasaki Annual Report 2009, P. 158, 2011/01

no abstracts in English

Journal Articles

Collective modes and Josephson vortices in a heterotic Josephson junction between single- and two-gap superconductors

Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*; Matsumoto, Hideki*

Physica C, 470(Suppl.1), p.S882 - S883, 2010/12

 Times Cited Count:0 Percentile:100(Physics, Applied)

We construct a theory of a heterotic Josephson junction between single- and two-gap superconductors. The theory predicts the presence of in-phase and out-of-phase collective modes of superconducting phases. The former is the Josephson plasma mode, and the latter is a counterpart of Leggett's mode in Josephson junctions. A signature for $$pm s$$-wave superconductivity is a drastic reduction of the frequency of the Josephson plasma mode. We also show that the magnetic field distribution of the Josephson vortex for $$pm s$$-wave superconductivity is more enlarged than that for s-wave without sign change between the order parameters.

Journal Articles

Theory and simulation of electromagnetic wave emission from intrinsic Josephson junctions

Machida, Masahiko; Ota, Yukihiro; Sasa, Narimasa; Koyama, Tomio*; Matsumoto, Hideki*

Journal of Physics; Conference Series, 248, p.012037_1 - 012037_8, 2010/11

 Times Cited Count:8 Percentile:7.88

no abstracts in English

Journal Articles

Anomalous Josephson vortex solutions in Josephson junctions with multiple tunneling channels

Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*; Matsumoto, Hideki*

Physica C, 470(20), p.1137 - 1140, 2010/11

 Times Cited Count:1 Percentile:92.29(Physics, Applied)

We construct a theory for Josephson junctions with multiple tunneling channels. We focus on two situations, i.e., a heterotic junction composed of two-gap-superconductor, insulator, and one-gap-superconductor, and a grain-boundary junction formed by two identical multi-gap superconductors. Then, we show that the magnetic field distribution of the Josephson vortex for $$pm$$s-wave superconductivity is more enlarged than that for s-wave without sign change between the order parameters. We display such anomalous vortices and suggest how to evaluate the enlargement.

Journal Articles

Ambegaokar-Baratoff relations for Josephson critical current in heterojunctions with multigap superconductors

Ota, Yukihiro; Nakai, Noriyuki; Nakamura, Hiroki; Machida, Masahiko; Inotani, Daisuke*; Ohashi, Yoji*; Koyama, Tomio*; Matsumoto, Hideki*

Physical Review B, 81(21), p.214511_1 - 214511_6, 2010/06

 Times Cited Count:25 Percentile:26.25(Materials Science, Multidisciplinary)

An extension of the Ambegaokar-Baratoff relation to a superconductor-insulator-superconductor (SIS) Josephson junction with multiple tunneling channels is derived. Applying the resultant relation to a SIS Josephson junction formed by an iron-based (five-band) and a single-band Bardeen-Cooper-Schrieffer (BCS) type superconductors, a theoretical bound of the Josephson critical current ($$I_{rm c}$$) multiplied by the resistance of the junction ($$R_{rm n}$$) is given. We reveal that such a bound is useful for identifying the pairing symmetry of iron-pnictide superconductors. One finds that if a measured value of $$I_{rm c}R_{rm n}$$ is smaller than the bound then the symmetry is $$pm s$$-wave, and otherwise $$s$$-wave without any sign changes. In addition, we stress that temperature dependence of $$I_{rm c}R_{rm n}$$ is sensitive to the difference of the gap functions from the BCS type gap formula in the above heterojunction.

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

Journal Articles

Theory of vortex structure in Josephson junctions with multiple tunneling channels; Vortex enlargement as a probe of $$pm$$$$s$$-wave superconductivity

Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*; Matsumoto, Hideki*

Physical Review B, 81(1), p.014502_1 - 014502_5, 2010/01

 Times Cited Count:18 Percentile:33.74(Materials Science, Multidisciplinary)

We theoretically study Josephson vortex structure in Josephson junctions which have multiple tunneling channels caused by multiple superconducting gaps. Deriving coupled sine-Gordon equation from the free energy taking account of the multiple tunneling channels, we examine two typical situations, a heterotic junctions composed of multi-gap superconductor, insulator, and single-gap superconductor, and a grain boundary junction formed by two identical multigap superconductors. Then, we reveal in both situations that the magnetic field distribution of the Josephson vortex for $$pm$$$$s$$-wave superconductivity is more enlarged than that for $$s$$-wave without sign change between the order parameters. Its mechanism is ascribed to a cancellation of the multiple Josephson currents. We display such an anomalous Josephson vortex and suggest how to evaluate the enlargement.

Journal Articles

Theory of heterotic superconductor-insulator-superconductor Josephson junctions between single- and multiple-gap superconductors

Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*; Matsumoto, Hideki*

Physical Review Letters, 102(23), p.237003_1 - 237003_4, 2009/06

 Times Cited Count:52 Percentile:10.48(Physics, Multidisciplinary)

Using the functional integral method, we construct a theory of heterotic superconductor-insulator-superconductor Josephson junctions between one- and two-gap superconductors. The theory predicts the presence of in-phase and out-of-phase collective oscillation modes of superconducting phases. The former corresponds to the Josephson plasma mode whose frequency is drastically reduced for $$pm$$ $$s$$-wave symmetry, and the latter is a counterpart of Leggett's mode in Josephson junctions. We also reveal that the critical current and the Fraunhofer pattern strongly depend on the symmetry type of the two-gap superconductor.

Journal Articles

Stripe formation in fermionic atoms on 2-D optical lattice; DMRG studies for $$n$$-leg repulsive Hubbard ladders

Machida, Masahiko; Okumura, Masahiko; Yamada, Susumu; Ohashi, Yoji*; Matsumoto, Hideki*

Journal of Superconductivity and Novel Magnetism, 22(3), p.275 - 279, 2009/04

 Times Cited Count:1 Percentile:92.93(Physics, Applied)

no abstracts in English

82 (Records 1-20 displayed on this page)