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論文

Orbit-based representation of equilibrium distribution functions for low-noise initialization of kinetic simulations of toroidal plasmas

Bierwage, A.; Di Troia, C.*; Briguglio, S.*; Vlad, G.*

Computer Physics Communications, 183(5), p.1107 - 1123, 2012/05

 被引用回数:10 パーセンタイル:55.99(Computer Science, Interdisciplinary Applications)

This work deals with the initial loading of phase space markers for global gyrokinetic particle-in-cell (PIC) simulations of plasmas that are magnetically confined in a toroidally axisymmetric configuration. A method is presented, which allows to prepare a marker distribution that is independent of time. This is achieved by loading markers on the toroidal surfaces of unperturbed guiding center orbits, where they are distributed uniformly in time. This allows to initialize global PIC codes with an accurate equilibrium distribution function and facilitates simulations with minimal noise-signal correlation. The concrete problem considered is the representation of energetic ions in tokamaks, which are characterized by large drifts across magnetic surfaces.

論文

Effects of complex symmetry-breakings on alpha particle power loads on first wall structures and equilibrium in ITER

篠原 孝司; Kurki-Suonio, T.*; Spong, D. A.*; Asunta, O.*; 谷 啓二*; Strumberger, E.*; Briguglio, S.*; Koskela, T.*; Vlad, G.*; G$"u$nter, S.*; et al.

Nuclear Fusion, 51(6), p.063028_1 - 063028_12, 2011/06

 被引用回数:45 パーセンタイル:86.53(Physics, Fluids & Plasmas)

Within the ITPA Topical Group on Energetic Particles, we have investigated the impact of the axisymmetry breaking of the tokamak in ITER. First, the validity of using a 2D equilibrium was investigated: a 3D equilibrium was reconstructed using the VMEC code, and it was verified that no 3D equilibrium reconstruction is needed but it is sufficient to add the vacuum field perturbations onto an 2D equilibrium. Then the alpha particle confinement was studied using ASCOT, and F3D OFMC codes. The distribution of the power load was found to depend on the first wall shape. We also made the first attempt to accommodate the effect of fast ion related MHD on the wall loads in ITER using the HMGC and ASCOT codes. The peak power flux to the wall was found to increase by an order of magnitude. Furthermore, the effect of 3D field which was produced by the ELM mitigation coil on the fast ion confinement was addressed by simulating NBI ions with the F3D OFMC code. The loss power fraction of NBI ions was found to increase from 0.3% to 4-5%.

論文

3D effect of ferromagnetic materials on alpha particle power loads on first wall structures and equilibrium on ITER

篠原 孝司; Kurki-Suonio, T.*; Spong, D.*; Asunta, O.*; 谷 啓二*; Strumberger, E.*; Briguglio, S.*; G$"u$nter, S.*; Koskela, T.*; Kramer, G.*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Within the ITPA Topical Group on Energetic Particles, we have investigated the impact of the axisymmetry breaking of the tokamak in ITER. First, the validity of using a 2D equilibrium was investigated: a 3D equilibrium was reconstructed using the VMEC code, and it was verified that no 3D equilibrium reconstruction is needed but it is sufficient to add the vacuum field perturbations onto an 2D equilibrium. Then the alpha particle confinement was studied using ASCOT, and F3D OFMC codes. The distribution of the power load was found to depend on the first wall shape. We also made the first attempt to accommodate the effect of fast ion related MHD on the wall loads in ITER using the HMGC and ASCOT codes. The peak power flux to the wall was found to increase by an order of magnitude. Furthermore, the effect of the ELM mitigation field on the fast ion confinement was addressed by simulating NBI ions with the F3D OFMC code. The loss power fraction of NBI ions was found to increase from 0.3% to 5.6%.

論文

Progress in the ITER physics basis, 5; Physics of energetic ions

Fasoli, A.*; Gormezano, C.*; Berk, H. L.*; Breizman, B.*; Briguglio, S.*; Darrow, D. S.*; Gorelenkov, N.*; Heidbrink, W. W.*; Jaun, A.*; Konovalov, S. V.*; et al.

Nuclear Fusion, 47(6), p.S264 - S284, 2007/06

 被引用回数:431 パーセンタイル:85.96(Physics, Fluids & Plasmas)

ITERや将来の核融合炉では高速イオンのアルファ粒子がプラズマの維持に重要な役割を果たし、高速イオンが関連した物理現象の理解は重要である。本論文では、1999年の最初の「ITER物理基盤の進展」に関するレポート以降の高速イオンが絡む高温プラズマの物理現象についての理解の進展についてまとめた。高速イオンの物理機構を理解するための高速イオン源の進展,トロイダル磁場リップルによる高速イオン閉じ込めの理解の進展,高速イオンと背景プラズマ起因MHDの相互作用の理解の進展,高速イオン起因MHDの線形安定性の理解の進展,高速イオンと高速イオン起因MHDの相互作用と非線形発展の理解の進展,高速イオン起因MHDによる高速イオンの輸送の理解の進展について、実験計測,理論,数値計算で得られた成果をまとめている。

論文

Particle simulation of bursting Alfv$'e$n modes in JT-60U

Briguglio, S.*; Fogaccia, G.*; Vlad, G.*; Zonca, F.*; 篠原 孝司; 石川 正男; 武智 学

Physics of Plasmas, 14(5), p.055904_1 - 055904_10, 2007/05

 被引用回数:42 パーセンタイル:79.66(Physics, Fluids & Plasmas)

The results of particle-in-cell simulations of a negative neutral beam heated Alfv$'e$n-mode experiment in the JT-60U are presented. They seem to match quite well the dynamics of the abrupt large-amplitude event (ALE) experimentally observed in the reference JT-60U discharge. The time scale and frequency spread of the ALE are well reproduced too. The issue of the weaker Alfv$'e$n fluctuation phase following the ALEs, characterized by fast frequency sweeping modes, is also investigated and an interpretation of the full JT-60U bursting-mode phenomenology is presented. Finally, the simulation tool is exploited by ad hoc synthetic diagnostics on the fast ion distribution function to get a deeper insight into the ALE nonlinear dynamics. The underlying fast-growing energetic particle mode saturates as resonant energetic ions are scattered out of the resonance region and displaced outwards. The radially displaced ions resonate with outer Alfv$'e$n modes and enhance their local drive.

論文

Particle simulation analysis of energetic-particle and Alfv$'e$n-mode dynamics in JT-60U discharges

Vlad, G.*; Briguglio, S.*; Fogaccia, G.*; 篠原 孝司; 石川 正男; 武智 学; Zonca, F.*

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

JT-60Uの負イオン源中性粒子ビームを用いたアルベン固有モード実験に対するHMGC particle-in-cellコードを用いた粒子数値計算である。ALEと呼ばれている不安定性について、線形成長過程では、高エネルギーイオン圧力勾配の強いところにたつアルベン連続スペクトルと強く相互作用した高エネルギー粒子駆動不安定性であることがわかった。非線形過程では高エネルギーイオンの輸送が観測され、時間スケールも含め、実験データを再現している。

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