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Journal Articles

The Martian surface radiation environment; A Comparison of models and MSL/RAD measurements

Matthi$"a$, D.*; Ehresmann, B.*; Lohf, H.*; K$"o$hler, J.*; Zeitlin, C.*; Appel, J.*; Sato, Tatsuhiko; Slaba, T. C.*; Martin, C.*; Berger, T.*; et al.

Journal of Space Weather and Space Climate (Internet), 6, p.A13_1 - A13_17, 2016/03

 Times Cited Count:60 Percentile:93.45(Astronomy & Astrophysics)

The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) has been measuring the radiation environment on the surface of Mars since August 6th 2012. In this work, several models such as GEANT4, PHITS, and HZETRN/OLTARIS are used to predict the radiation environment caused by galactic cosmic rays on Mars in order to compare and validate them with the experimental results. Although good agreement is found in many cases for GEANT4, PHITS and HZETRN/OLTARIS, some models still show large, sometimes order of magnitude, discrepancies in certain particle spectra. We have found that RAD data is helping make better choices of input parameters and physical models. These results help to predict dose rates for future manned missions as well as to perform shield optimization studies.

Journal Articles

Approach for efficient linear MHD analysis without spectrum pollution in tokamaks

Aiba, Nobuyuki; Cooper, W.*; Gruber, R.*

Europhysics Conference Abstracts (Internet), 36F, p.P2.045_1 - P2.045_4, 2012/00

We developed a new numerical method for analyzing linear ideal MHD stability with higher-order finite element. Since the linear ideal MHD problem is a typical ill-posed problem from numerical viewpoints, a kind of numerical instability, called spectrum pollution, sometimes appears. About 30 years ago, a method realizing to suppress this numerical instability was developed, but this cannot fully suppress this. In fact, when the radial mesh number decreases, numerical instability appears. After revisiting this method, we found that the numerical integral method in this method is not appropriate for suppressing this instability. To fix this issue, we developed a new method with Gauss-Legendre quadrature, and realized to fully suppress numerical instability. This method can apply to the stability analysis with plasma rotation.

Journal Articles

Status of JT-60SA tokamak under the EU-JA broader approach agreement

Matsukawa, Makoto; Kikuchi, Mitsuru; Fujii, Tsuneyuki; Fujita, Takaaki; Hayashi, Takao; Higashijima, Satoru; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Ide, Shunsuke; Ishida, Shinichi; et al.

Fusion Engineering and Design, 83(7-9), p.795 - 803, 2008/12

 Times Cited Count:17 Percentile:72.99(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Progress in the ITER physics basis, 3; MHD stability, operational limits and disruptions

Hender, T. C.*; Wesley, J. C.*; Bialek, J.*; Bondeson, A.*; Boozer, A. H.*; Buttery, R. J.*; Garofalo, A.*; Goodman, T. P.*; Granetz, R. S.*; Gribov, Y.*; et al.

Nuclear Fusion, 47(6), p.S128 - S202, 2007/06

 Times Cited Count:879 Percentile:100(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

The "Hybrid" scenario in JET; Towards its validation for ITER

Joffrin, E.*; Sips, A. C. C.*; Artaud, J. F.*; Becoulet, A.*; Bertalot, L.*; Budny, R.*; Buratti, P.*; Belo, P.*; Challis, C. D.*; Crisanti, F.*; et al.

Nuclear Fusion, 45(7), p.626 - 634, 2005/07

 Times Cited Count:92 Percentile:93.18(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Progress in physics basis and its impact on ITER

Shimada, Michiya; Campbell, D.*; Stambaugh, R.*; Polevoi, A. R.*; Mukhovatov, V.*; Asakura, Nobuyuki; Costley, A. E.*; Donn$'e$, A. J. H.*; Doyle, E. J.*; Federici, G.*; et al.

Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11

This paper summarises recent progress in the physics basis and its impact on the expected performance of ITER. Significant progress has been made in many outstanding issues and in the development of hybrid and steady state operation scenarios, leading to increased confidence of achieving ITER's goals. Experiments show that tailoring the current profile can improve confinement over the standard H-mode and allow an increase in beta up to the no-wall limit at safety factors $$sim$$ 4. Extrapolation to ITER suggests that at the reduced plasma current of $$sim$$ 12MA, high Q $$>$$ 10 and long pulse ($$>$$1000 s) operation is possible with benign ELMs. Analysis of disruption scenarios has been performed based on guidelines on current quench rates and halo currents, derived from the experimental database. With conservative assumptions, estimated electromagnetic forces on the in-vessel components are below the design target values, confirming the robustness of the ITER design against disruption forces.

Journal Articles

The "hybrid" scenario in JET; Towards its validation for ITER

Joffrin, E.*; Sips, A. C. C.*; Artaud, J. F.*; Becoulet, A.*; Budny, R.*; Buratti, P.*; Belo, P.*; Challis, C. D.*; Crisanti, F.*; de Baar, M.*; et al.

Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11

no abstracts in English

Journal Articles

Off-axis neutral beam current drive experiments on ASDEX Upgrade and JT-60U

Hobirk, J.*; Oikawa, Toshihiro; Fujita, Takaaki; Fukuda, Takeshi; G$"u$nter, S.*; Gruber, O.*; Isayama, Akihiko; Kamada, Yutaka; Kikuchi, Mitsuru; Maraschek, M.*; et al.

Europhysics Conference Abstracts (CD-ROM), 27A, 4 Pages, 2003/00

no abstracts in English

Journal Articles

Neutral point validation studies on JT-60U, alcator C-Mod and ASDEX-upgrade tokamaks

Nakamura, Yukiharu; Yoshino, Ryuji; Granetz, R. S.*; Pautasso, G.*; Gruber, O.*; Jardin, S. C.*

Purazuma, Kaku Yugo Gakkai-Shi, 78(4), p.347 - 355, 2002/04

no abstracts in English

Journal Articles

Characterization of disruption phenomenology in ITER

Yoshino, Ryuji; D.J.Campbell*; E.Fredrickson*; Fujisawa, Noboru; N.Granetz*; Gruber, O.*; T.C.Hender*; D.A.Humphreys*; N.Ivanov*; S.Jardin*; et al.

Fusion Energy 2000 (CD-ROM), 4 Pages, 2001/05

no abstracts in English

Oral presentation

Impact of plasma rotation on linear MHD physics in tokamaks; Theory and numerical applications

Aiba, Nobuyuki; Shiraishi, Junya; Hirota, Makoto; Cooper, W.*; Gruber, R.*

no journal, , 

The authors identified that plasma poloidal rotation sometimes plays an important role for ideal MHD stability due to changing the Doppler-shift frequency. As the result, the stability of edge localized MHD mode can depends on the direction of toroidal rotation; this dependence is qualitatively consistent with the experimental results observed in JT-60U. Plasma rotation is also responsible for the stability of resistive wall mode (RWM). In reversed shear plasmas, plasma rotation once stabilize RWM but destabilize this again when rotation frequency reaches to certain frequency. This re-destabilization is thought to be related to the coupling between RWM and a stable MHD wave. By developing a new numerical matching method, we realize to identify rotation effect on RWM stability in more detail, and as one of examples, we identified the most important resonant surface responsible for stabilizing RWM.

Oral presentation

Numerical method for linear MHD stability analysis without spectrum pollution

Aiba, Nobuyuki; Cooper, W. A.*; Gruber, R.*

no journal, , 

When linear MHD stability is analyzed numerically, it is well-known that numerical instability called "spectrum pollution" sometimes appears. This numerical instability is usually caused due to inadequate choice of basis functions of finite elements, and the numerical method fixing this problem, named as Hybrid-Element-Method, was developed about 30 years ago. However, we identified that this instability is also caused due to missing to adopt numerical integral method. From both the viewpoint of basis functions and that of numerical integral method, we developed the new numerical method for linear MHD stability with Hybrid-Element-Method in combination with Gauss-Legendre quadrature. This new method realizes to suppress completely numerical instability even when plasma rotates.

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