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Journal Articles

Monte Carlo modelling for the ${it in vivo}$ lung monitoring of enriched uranium; Results of an international comparison

Broggio, D.*; Bento, J.*; Caldeira, M.*; Cardenas-Mendez, E.*; Farah, J.*; Fonseca, T.*; Konvalinka, C.*; Liu, L.*; Perez, B.*; Capello, K.*; et al.

Radiation Measurements, 47(7), p.492 - 500, 2012/07

 Times Cited Count:16 Percentile:17.59(Nuclear Science & Technology)

Journal Articles

ITER test blanket module error field simulation experiments at DIII-D

Schaffer, M. J.*; Snipes, J. A.*; Gohil, P.*; de Vries, P.*; Evans, T. E.*; Fenstermacher, M. E.*; Gao, X.*; Garofalo, A. M.*; Gates, D. A.*; Greenfield, C. M.*; et al.

Nuclear Fusion, 51(10), p.103028_1 - 103028_11, 2011/10

 Times Cited Count:32 Percentile:15.51(Physics, Fluids & Plasmas)

Experiments at DIII-D investigated the effects of ferromagnetic error fields similar to those expected from proposed ITER Test Blanket Modules (TBMs). Studied were effects on: plasma rotation and locking; confinement; L-H transition; edge localized mode (ELM) suppression by resonant magnetic perturbations; ELMs and the H-mode pedestal; energetic particle losses; and more. The experiments used a 3-coil mock-up of 2 magnetized ITER TBMs in one ITER equatorial port. The experiments did not reveal any effect likely to preclude ITER operations with a TBM-like error field. The largest effect was slowed plasma toroidal rotation v across the entire radial profile by as much as $$Delta v/v_{0} sim 50%$$ via non-resonant braking. Changes to global $$Delta n/n_{0}$$, $$Delta v/v_{0}$$ and $$Delta H_{98}/H_{98,0}$$ were $$sim$$3 times smaller. These effects are stronger at higher $$beta$$ and lower $$v_{0}$$. Other effects were smaller.

Journal Articles

Monte Carlo modelling of Germanium detectors for the measurement of low energy photons in internal dosimetry; Results of an international comparison

G$'o$mez-Ros, J.-M.*; de Carlan, L.*; Franck, D.*; Gualdrini, G.*; Lis, M.*; L$'o$pez, M. A.*; Moraleda, M.*; Zankl, M.*; Badal, A.*; Capello, K.*; et al.

Radiation Measurements, 43(2-6), p.510 - 515, 2008/02

 Times Cited Count:22 Percentile:16.27(Nuclear Science & Technology)

This communication summarizes the results concerning the Monte Carlo modeling of Germanium detectors for the measurement of low energy photons arising from the "International comparison on MC modeling for in vivo measurement of Americium in a knee phantom" organized within the EU Coordination Action CONRAD (Coordinated Network for Radiation Dosimetry) as a joint initiative of EURADOS working groups 6 (computational dosimetry) and 7 (internal dosimetry).

Journal Articles

Observation of confinement degradation of energetic ions due to Alfv$'e$n eigenmodes in JT-60U weak shear plasmas

Ishikawa, Masao; Takechi, Manabu; Shinohara, Koji; Kusama, Yoshinori; Matsunaga, Go; Krasilnikov, V. A.*; Kashuck, Y.*; Isobe, Mitsutaka*; Nishitani, Takeo; Sukegawa, Atsuhiko; et al.

Nuclear Fusion, 46(10), p.S898 - S903, 2006/10

 Times Cited Count:13 Percentile:56.9(Physics, Fluids & Plasmas)

Confinement degradation of energetic ions due to Alfv$'e$n eigenmodes (AEs) has been investigated with negative ion based neutral beam injection into JT-60U weak shear plasmas. AEs with a rapid frequency sweeping and then saturation as the minimum value of the safety factor decreases have been observed. This frequency behaviour can be explained by RSAE and the transition from RSAEs toTAEs. The associated change in the charge exchange neutral particle flux suggests energetic ion transport due to these AEs. The total neutron emission reduction rate in the presence of these AEs is evaluated by calculation using the orbit following Monte-Carlo code taking into account the change in bulk plasmas. The evaluation indicates confinement of energetic ions is degraded due to these AEs. In particular, it is found that the confinement degradation of energetic ions is maximum during the transition from RSAEs to TAEs.

Journal Articles

Energetic ion transport by abrupt large-amplitude event induced by negative-ion-based neutral beam injection in the JT-60U

Ishikawa, Masao; Takechi, Manabu; Shinohara, Koji; Kusama, Yoshinori; Cheng, C. Z.*; Matsunaga, Go; Todo, Yasushi*; Gorelenkov, N. N.*; Kramer, G. J.*; Nazikian, R. M.*; et al.

Nuclear Fusion, 45(12), p.1474 - 1480, 2005/12

 Times Cited Count:35 Percentile:23.98(Physics, Fluids & Plasmas)

To investigate energetic ion transport induced by Alfven eigenmodes (AEs) the neutron emission profile measurement and the charge exchange (CX) neutral particle flux measurement by Natural Diamond Detector has been performed simultaneously in the JT-60U for the first time. The energetic ion profiles inferred from these measurements indicate that ALEs cause a radial redistribution of energetic ions of limited energy range from the core region to the outer region of the plasma in weak shear plasmas. This energy range is consistent with the resonance condition between the mode and the energetic ions. In reversed shear plasmas, reversed-shear-induced AEs (RSAEs) and their transition to TAEs as the minimum value of the safety factor decreases has been observed. Neutron measurements suggest energetic ion loss is large in the transition phase from RSAEs to TAEs.

Journal Articles

Alfv$'e$n eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection discharges

Takechi, Manabu; Fukuyama, Atsushi*; Ishikawa, Masao; Cheng, C. Z.*; Shinohara, Koji; Ozeki, Takahisa; Kusama, Yoshinori; Takeji, Satoru*; Fujita, Takaaki; Oikawa, Toshihiro; et al.

Physics of Plasmas, 12(8), p.082509_1 - 082509_7, 2005/08

 Times Cited Count:29 Percentile:30.47(Physics, Fluids & Plasmas)

Rapid frequency sweeping modes observed in reversed magnetic shear (RS) plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) have been identified as Reversed-Shear-induced Alfv$'e$n Eigenmodes (RSAEs), which are ideal MHD Alfv$'e$n eigenmodes (AEs) localized to the region of minimum safety factor, $$q_{rm min}$$, and are excited by negative-ion-based neutral beam injection. The chirping and subsequent saturation of the mode frequency are consistent with theoretical predictions for the transition from RSAEs to Toroidal Alfv$'{e}$n eigenmodes (TAEs). The previously observed rapid frequency sweeping modes in ion cyclotron wave heated plasmas in JT-60U can also be similarly explained. The observed AE amplitude is largest during the transition from RSAEs to TAEs, and fast ion loss is observed when the AE amplitude is largest at this transition. It is preferable to operate outside the transition range of $$q$$$$_{min}$$, e.g., 2.4 $$<$$ $$q$$$$_{min}$$ $$<$$ 2.7 for the n = 1 AE to avoid substantial fast ion loss in RS plasmas.

Journal Articles

Role of bremsstrahlung radiation in limiting the energy of runaway electrons in Tokamaks

Bakhtiari, M.; Kramer, G. J.*; Takechi, Manabu; Tamai, Hiroshi; Miura, Yukitoshi; Kusama, Yoshinori; Kamada, Yutaka

Physical Review Letters, 94(21), p.215003_1 - 215003_4, 2005/06

 Times Cited Count:38 Percentile:18.18(Physics, Multidisciplinary)

Bremsstrahlung radiation of runaway electrons is found to be an energy limit for runaway electrons in tokamaks. The minimum and maximum energy of runaway electron beams is shown to be limited by collisions and Bremsstrahlung radiation, respectively. It is also found that a massive injection of a high-Z gas such as Xenon can terminate a disruption-generated runaway current before the runaway electrons hit the walls.

Journal Articles

Study of plasma termination using high-Z noble gas puffing in the JT-60U tokamak

Bakhtiari, M.; Tamai, Hiroshi; Kawano, Yasunori; Kramer, G. J.*; Isayama, Akihiko; Nakano, Tomohide; Kamiya, Kensaku; Yoshino, Ryuji; Miura, Yukitoshi; Kusama, Yoshinori; et al.

Nuclear Fusion, 45(5), p.318 - 325, 2005/05

 Times Cited Count:40 Percentile:19.89(Physics, Fluids & Plasmas)

In the previous works we had shown that injecting a mixture of large amounts of hydrogen and small amounts of argon can terminate a tokamak discharge quickly with avoiding runaway electron generation. In this work we have done the same experiments but with different gases in addition to argon. In fact we compared the effect of the puffing of argon, krypton, and xenon gases with and without simultaneous hydrogen gas puffing on disruption mitigation. We observed that injecting all impurities in the form of an admixture in hydrogen lead to faster plasma shutdowns with less runaway electron generation. We also found that injecting krypton gas (with or without hydrogen) seems to be a good candidate for plasma shutdown purposes since it induces low heat flux to divertor plates and avoids runaway electron generation more effectively.

Journal Articles

Energetic particle physics in JT-60U and JFT-2M

Shinohara, Koji; Takechi, Manabu; Ishikawa, Masao; Kusama, Yoshinori; Tsuzuki, Kazuhiro; Urata, Kazuhiro*; Kawashima, Hisato; Tobita, Kenji; Fukuyama, Atsushi*; Cheng, C. Z.*; et al.

Plasma Physics and Controlled Fusion, 46(7), p.S31 - S45, 2004/07

 Times Cited Count:40 Percentile:20.43(Physics, Fluids & Plasmas)

Recent energetic particle physics research has been devoted to Alfven eigenmodes (AEs) in reversed-shear (RS) plasmas, energetic ion transport in the appearance of modes in the frequency range of TAE, energetic ion behavior in the plasma with a current hole, and ripple loss in the complex toroidal field ripple due to ferritic steel plates. We will report these recent progresses for energetic particle physics in JT-60U and JFT-2M.

Journal Articles

Relationship between particle and heat transport in JT-60U plasmas with internal transport barrier

Takenaga, Hidenobu; Higashijima, Satoru; Oyama, Naoyuki; Bruskin, L. G.; Koide, Yoshihiko; Ide, Shunsuke; Shirai, Hiroshi; Sakamoto, Yoshiteru; Suzuki, Takahiro; Hill, K. W.*; et al.

Nuclear Fusion, 43(10), p.1235 - 1245, 2003/10

 Times Cited Count:62 Percentile:11.61(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Energetic particle experiments in JT-60U and their implications for a fusion reactor

Tobita, Kenji; Kusama, Yoshinori; Shinohara, Koji; Nishitani, Takeo; Kimura, Haruyuki; Kramer, G. J.*; Nemoto, Masahiro*; Kondoh, Takashi; Oikawa, Toshihiro; Morioka, Atsuhiko; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.315 - 326, 2002/09

 Times Cited Count:8 Percentile:49.35(Nuclear Science & Technology)

Energetic particle experiments in JT-60U are summarized, mainly covering ripple loss and Alfven eigenmodes (AE modes). Significant loss was observed for 85 keV NBI ions and fusion-produced tritons increased when toroidal field ripple at the plasma surface, especially in reversed shear plasma. Measurement of hot spots on the first wall due to ripple loss confirmed agreement with code predictions, validating the modeling incorporated in an orbit-following Monte Carlo code. A variety of AE modes were destabilized in ICRF minority heating and negative-ion-based NBI (N-NBI) heating. Most of the observed modes are gap modes identified to be TAE, EAE and NAE. Interesting finding is pulsating modes accompanying frequency sweep, which were destabilized by N-NBI and sometimes induced a beam ion loss of up to 25%. Also presented are energetic particle issues in auxiliary heating with ICRF and N-NBI.

Journal Articles

Recent progress of Alfv$'e$n eigenmode experiments using N-NB in JT-60U tokamak

Shinohara, Koji; Takechi, Manabu; Ishikawa, Masao*; Kusama, Yoshinori; Morioka, Atsuhiko; Oyama, Naoyuki; Tobita, Kenji; Ozeki, Takahisa; JT-60 Team; Gorelenkov, N. N.*; et al.

Nuclear Fusion, 42(8), p.942 - 948, 2002/08

 Times Cited Count:37 Percentile:23.68(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Magnetic safety factor profile before and after sawtooth crashes investigated with toroidicity and ellipticity induced Alfv$'e$n eigenmodes

Kramer, G. J.; Cheng, C. Z.*; Kusama, Yoshinori; Nazikian, R. M.*; Takeji, Satoru; Tobita, Kenji

Nuclear Fusion, 41(9), p.1135 - 1151, 2001/09

 Times Cited Count:32 Percentile:28.71(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Alf$'e$n eigenmodes driven by Alf$'e$nic beam ions in JT-60U

Shinohara, Koji; Kusama, Yoshinori; Takechi, Manabu; Morioka, Atsuhiko; Ishikawa, Masao*; Oyama, Naoyuki; Tobita, Kenji; Ozeki, Takahisa; Takeji, Satoru; Moriyama, Shinichi; et al.

Nuclear Fusion, 41(5), p.603 - 612, 2001/05

 Times Cited Count:75 Percentile:9.4(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Fast particle experiments in JT-60U

Kramer, G. J.; Iwase, Makoto; Kusama, Yoshinori; Morioka, Atsuhiko; Nemoto, Masahiro; Nishitani, Takeo; Shinohara, Koji; Takeji, Satoru; Tobita, Kenji; Ozeki, Takahisa; et al.

Nuclear Fusion, 40(7), p.1383 - 1396, 2000/07

 Times Cited Count:44 Percentile:20.87(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Stability of reversed shear discharges in JT-60U

Takeji, Satoru; Tokuda, Shinji; Fujita, Takaaki; Isayama, Akihiko; Ishii, Yasutomo; Kamada, Yutaka; Suzuki, Takahiro; Yoshino, Ryuji; Ide, Shunsuke; Ozeki, Takahisa; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 76(6), p.575 - 584, 2000/06

no abstracts in English

Journal Articles

Characteristics of Alfv$'e$n eigenmodes, burst modes and chirping modes in the Alfv$'e$n frequency range driven by negative ion based neutral beam injection in JT-60U

Kusama, Yoshinori; Kramer, G. J.; Kimura, Haruyuki; Saigusa, Mikio*; Ozeki, Takahisa; Tobita, Kenji; Oikawa, Toshihiro; Shinohara, Koji; Kondoh, Takashi; Moriyama, Shinichi; et al.

Nuclear Fusion, 39(11Y), p.1837 - 1843, 1999/11

 Times Cited Count:61 Percentile:13.16(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Frequency chirping of core-localized toroidicity-induced Alfv$'e$n eigenmodes and their coupling to global Alfv$'e$n eigenmodes

Kramer, G. J.; Cheng, C. Z.*; Fu, G. Y.*; Kusama, Yoshinori; Nazikian, R. M.*; Ozeki, Takahisa; Tobita, Kenji

Physical Review Letters, 83(15), p.2961 - 2964, 1999/10

 Times Cited Count:22 Percentile:24.95(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

ICRF heating of plasmas with internal transport barrier during reversed magnetic shear experiments in JT-60U

Iwase, Makoto; Koide, Yoshihiko; Tobita, Kenji; Moriyama, Shinichi; Takenaga, Hidenobu; Fujita, Takaaki; Shirai, Hiroshi; Kusama, Yoshinori; Nemoto, Masahiro; Oikawa, Toshihiro; et al.

Proc. of 13th Topical Conf. on Applications of Radio Frequency Power to Plasmas, p.116 - 119, 1999/04

no abstracts in English

Journal Articles

Destabilization of ellipticity-induced Alfven eigenmodes during ICRF heating and stabilization by negative-ion-based neutral beam injection in JT-60U

Kusama, Yoshinori; Fu, G. Y.*; Kramer, G. J.*; Saigusa, Mikio*; Oikawa, Toshihiro; Ozeki, Takahisa; Moriyama, Shinichi; Tchernychev, F. V.*; Nemoto, Masahiro; Kondoh, Takashi; et al.

Plasma Physics and Controlled Fusion, 41(9), p.1167 - 1177, 1999/00

 Times Cited Count:5 Percentile:78.81(Physics, Fluids & Plasmas)

no abstracts in English

30 (Records 1-20 displayed on this page)