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Journal Articles

Size and dopant-concentration dependence of photoluminescence properties of ion-implanted phosphorus- and boron-codoped Si nanocrystals

Nakamura, Toshihiro*; Adachi, Sadao*; Fujii, Minoru*; Sugimoto, Hiroshi*; Miura, Kenta*; Yamamoto, Shunya

Physical Review B, 91(16), p.165424_1 - 165424_8, 2015/04

 Times Cited Count:13 Percentile:57.42(Materials Science, Multidisciplinary)

Semiconductor nanocrystals have unique electrical and optical properties, because of the quantum confinement effect, and the doping of impurities into nanocrystals. In this study, we investigated the photoluminescence (PL) properties of phosphorus- (P) and boron- (B) co-doped Si nanocrystals (Si NCs), which was synthesized using an ion implantation technique. The Si-NC size (average diameter: 3.5, 4.4, 5.2 nm) and the P and B ion doses (0.1-4.5$$times$$10$$^{16}$$ cm$$^{-2}$$)values were systematically varied. We find that the PL peak energy shifts to lower values with increasing the average diameters of Si NCs and PB ion dose. The results of PL measurements indicate that the PL spectra are due to the band-to-band transition at the reduced Si-NC band gap caused by the formation of impurity and the radiative transitions between defect- and/or impurity-related localized states. It was found that the PL properties can be controlled by varying the Si-NC size as well as the dopant concentration.

Journal Articles

Phosphorus and boron codoping of silicon nanocrystals by ion implantation; Photoluminescence properties

Nakamura, Toshihiro*; Adachi, Sadao*; Fujii, Minoru*; Miura, Kenta*; Yamamoto, Shunya

Physical Review B, 85(4), p.045441_1 - 045441_7, 2012/01

 Times Cited Count:24 Percentile:72.65(Materials Science, Multidisciplinary)

Silicon nanocrystals (Si-nc's) such as nanometer-sized Si dots embedded in a SiO$$_{2}$$ matrix and porous Si have been intensively investigated because of their interesting photoluminescence (PL) properties. Si-nc's exhibit strong and visible emission at room temperature. Because of their compatibility with Si-based technology, light-emitting Si-nc's are an attractive candidate for materials used in various optoelectronic device applications. In this study, the PL properties of n- and p-type dopants phosphorus (P) and boron (B) co-doped Si-nc's prepared by the ion implantation were studied. For (P, B) co-doped Si-nc's, the donor-acceptor (D-A)-pair recombination emission was clearly observed on the long-wavelength side of the intrinsic Si-nc emission. The D-A-pair recombination energy is found to be smaller than the band-gap energy of bulk Si and is strongly dependent on the number of P and B impurities doped in a Si-nc's.

Journal Articles

Response functions of Phoswich-type neutron detector for high-energy cosmic ray neutron measurement

Takada, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*; Nakamura, Takashi*; Baba, Mamoru*; Homma, Toshihiro*; Endo, Akira; Tanimura, Yoshihiko

Journal of Nuclear Science and Technology, 47(10), p.917 - 931, 2010/10

 Times Cited Count:6 Percentile:43.83(Nuclear Science & Technology)

A phoswich-type neutron detector was developed in order to measure high-energy cosmic-ray neutron spectrum in aircrafts. The neutron detector consists of a 121.7 mm diameter and a 121.7 mm long EJ309 organic liquid scintillator covered with a 15 mm thick EJ299-13 outer plastic scintillator. Neutron response functions of the detector are required for an unfolding method to get the energy spectrum. The neutron response functions were evaluated from measurements using quasi-monoenergetic neutron sources of various peak energies from 35 to 78 MeV and from the MCNPX simulation. Light output and scintillation attenuation in the scintillator were measured for proton, deuteron and helium-ion beams. The measured neutron response functions well agreed with the MCNPX simulation. Neutron response matrix was created up to 300 MeV neutron energy based on the MCNPX simulation in order to cover the wide neutron energy range in the fight experiment. Photon response matrix also was created up to 50 MeV.

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

Report on ITPA (International Tokamak Physics Activity) meeting, 22

Takenaga, Hidenobu; Ogawa, Yuichi*; Takizuka, Tomonori; Yagi, Masatoshi*; Yamada, Hiroshi*; Sakamoto, Yoshiteru; Toi, Kazuo*; Fukuda, Takeshi*; Fukuyama, Atsushi*; Fujita, Takaaki; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 84(7), p.465 - 467, 2008/07

no abstracts in English

Journal Articles

Progress in R&D efforts on the energy recovery linac in Japan

Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.

Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06

Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.

Journal Articles

Report of ITPA (International Tokamak Physics Activity) meetings, 21

Kawahata, Kazuo*; Kawano, Yasunori; Kusama, Yoshinori; Mase, Atsushi*; Sasao, Mamiko*; Ide, Shunsuke; Oikawa, Toshihiro; Suzuki, Takahiro; Takase, Yuichi*; Nakamura, Yukio*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 84(5), p.297 - 298, 2008/05

no abstracts in English

Journal Articles

Report of meetings of ITPA (International Tokamak Physics Activity), 19

Sasao, Mamiko*; Kusama, Yoshinori; Kawano, Yasunori; Kawahata, Kazuo*; Mase, Atsushi*; Sugie, Tatsuo; Fujita, Takaaki; Fukuda, Takeshi*; Fukuyama, Atsushi*; Sakamoto, Yoshiteru; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 83(9), p.779 - 782, 2007/09

This is a report of highlights from 2007 spring meetings of seven Topical Groups (TG) of International Tokamak Physics Activity (ITPA). In each meeting, high priority issues in physics of International Thermonuclear Experimental Reactor (ITER) and other burning plasma experiments have been discussed and investigated. Twenty-seven scientists from Japan have participated in those meetings. Dates and places of the meetings are shown below. (1) Diagnostics TG: 26-30 March, Princeton (USA), (2) Transport Physics TG: 7-10 May, Lausanne (Switzerland), (3) Confinement Database and Modeling TG: 7-10 May, Lausanne (Switzerland), (4) Edge Pedestal Physics TG: 7-10 May, Garching (Germany) (5) Steady State Operation TG: 9-11 May, Daejeon (South Korea), (6)MHD TG: 21-24 May, San Diego (USA), (7) Scrape-off-layer and Divertor Physics TG: 7-10 May, Garching (Germany).

Journal Articles

Report on ITPA (International Tokamak Physics Activity) meeting, 18

Kawahata, Kazuo*; Kawano, Yasunori; Kusama, Yoshinori; Mase, Atsushi*; Sasao, Mamiko*; Sugie, Tatsuo; Fujita, Takaaki; Fukuda, Takeshi*; Fukuyama, Atsushi*; Sakamoto, Yoshiteru; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 83(2), p.195 - 198, 2007/02

no abstracts in English

Journal Articles

Soft X-ray absorption spectroscopy and magnetic circular dichroism study of electroless-deposited CoNiFe ternary alloy soft magnetic films

Tanaka, Masahito*; Nakamura, Naomichi*; Asahi, Toru*; Tsumori, Toshihiro*; Agui, Akane; Mizumaki, Masaichiro*; Osaka, Tetsuya*

Physica Status Solidi (C), 3(8), p.2783 - 2786, 2006/09

 Times Cited Count:1 Percentile:47.52

no abstracts in English

Journal Articles

Report of ITPA (International Tokamak Physics Activity) meetings, 17

Asakura, Nobuyuki; Kato, Takako*; Nakano, Tomohide; Takamura, Shuichi*; Tanabe, Tetsuo*; Iio, Shunji*; Nakajima, Noriyoshi*; Ono, Yasushi*; Ozeki, Takahisa; Takechi, Manabu; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 82(7), p.448 - 450, 2006/07

no abstracts in English

Journal Articles

Report on ITPA (International Tokamak Physics Activity) meeting, 16

Sakamoto, Yoshiteru; Toi, Kazuo*; Fukuda, Takeshi*; Fukuyama, Atsushi*; Fujita, Takaaki; Ogawa, Yuichi*; Takizuka, Tomonori; Takenaga, Hidenobu; Yagi, Masatoshi*; Yamada, Hiroshi*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 82(2), p.109 - 110, 2006/02

no abstracts in English

Journal Articles

Operation of JAERI AVF cyclotron system

Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; Kurashima, Satoshi; Yoshida, Kenichi; Fukuda, Mitsuhiro; Okumura, Susumu; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Nakamura, Yoshiteru; et al.

JAEA-Review 2005-001, TIARA Annual Report 2004, P. 370, 2006/01

no abstracts in English

Journal Articles

Report on ITPA (International Tokamak Physics Activity) meeting, 14

Sakamoto, Yoshiteru; Toi, Kazuo*; Fukuda, Takeshi*; Fukuyama, Atsushi*; Fujita, Takaaki; Ogawa, Yuichi*; Takizuka, Tomonori; Takenaga, Hidenobu; Yagi, Masatoshi*; Yamada, Hiroshi*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 81(8), p.626 - 627, 2005/08

no abstracts in English

Journal Articles

Status report on JAERI-AVF cyclotron system

Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; Kurashima, Satoshi; Yoshida, Kenichi; Fukuda, Mitsuhiro; Okumura, Susumu; Miyawaki, Nobumasa; Nakamura, Yoshiteru; Akaiwa, Katsuhiro*; et al.

Proceedings of 1st Annual Meeting of Particle Accelerator Society of Japan and 29th Linear Accelerator Meeting in Japan, p.209 - 211, 2004/08

no abstracts in English

Journal Articles

Fusion plasma performance and confinement studies on JT-60 and JT-60U

Kamada, Yutaka; Fujita, Takaaki; Ishida, Shinichi; Kikuchi, Mitsuru; Ide, Shunsuke; Takizuka, Tomonori; Shirai, Hiroshi; Koide, Yoshihiko; Fukuda, Takeshi; Hosogane, Nobuyuki; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.185 - 254, 2002/09

 Times Cited Count:28 Percentile:48.48(Nuclear Science & Technology)

With the main aim of providing physics basis for ITER and the steady-state tokamak reactors, JT-60/JT-60U has been developing and optimizing the operational concepts, and extending the discharge regimes toward sustainment of high integrated performance in the reactor relevant parameter regime. In addition to achievement of the equivalent break-even condition (QDTeq up to 1.25) and a high fusion triple product = 1.5E21 m-3skeV, JT-60U has demonstrated the integrated performance of high confinement, high beta-N, full non-inductive current drive with a large fraction of bootstrap current in the reversed magnetic shear and in the high-beta-p ELMy H mode plasmas characterized by both internal and edge transport barriers. The key factors in optimizing these plasmas are profile and shape controls. As represented by discovery of various Internal Transport Barriers, JT-60/JT-60U has been emphasizing freedom and restriction of profiles in various confinement modes. JT-60U has demonstrated applicability of these high confinement modes to ITER and also clarified remaining issues.

JAEA Reports

Estimation of biases for inserted reactivity estimation of JCO criticality accident

Yamamoto, Toshihiro; Nakamura, Takemi*; Miyoshi, Yoshinori

JAERI-Data/Code 2001-001, 30 Pages, 2001/02

JAERI-Data-Code-2001-001.pdf:1.53MB

no abstracts in English

Journal Articles

Status report on the JAERI AVF cyclotron system

Nakamura, Yoshiteru; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; Tamura, Hiroyuki; Kurashima, Satoshi; Yokota, Wataru; Okumura, Susumu; Fukuda, Mitsuhiro; Akaiwa, Katsuhiro*; et al.

Proceedings of 13th Symposium on Accelerator Science and Technology, p.193 - 195, 2001/00

The AVF cyclotron system at JAERI Takasaki has been smoothly operated without serious troubles since the first beam extraction in March, 1991. A yearly operation time is about 3200 hours on an average for recent eight years. In last two years, we performed some improvements and developments as followings: stabilization of the cyclotron beam by addition on an exclusive cooling system, designing and investigation of the flat-top system using fifth-harmonic RF, reconstruction of the rotary shutter for radiation shielding and reinforcement of the magnetic channel and its power supply. Furthermore, the renewal of main circulation pump for cooling system, replacement of shunt resistor in the power supplies and re-alignment of the several magnets along the trunk beam transport line were also carried out.

Journal Articles

Fission source convergence of Monte Carlo criticality calculations in weakly coupling fissile arrays

Yamamoto, Toshihiro; Nakamura, Takemi*; Miyoshi, Yoshinori

Journal of Nuclear Science and Technology, 37(1), p.41 - 52, 2000/01

no abstracts in English

Oral presentation

Soft X-ray absorption spectroscopy and magnetic circular dichroism study of electroless-deposited CoNiFe ternary alloy soft magnetic film

Tanaka, Masahito*; Nakamura, Naomichi*; Asahi, Toru*; Osaka, Tetsuya*; Tsumori, Toshihiro*; Agui, Akane; Mizumaki, Masaichiro*

no journal, , 

no abstracts in English

32 (Records 1-20 displayed on this page)