第4回先端エネルギー理工学セミナー

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記
対象：大学院学生(修士、博士)
For master students and Ph.D. students
日時：2015 年 2 月 6 日（金）14:50-16:20
Feb. 6, 2015 (Fri.) 14:50-16:20
場所：総合理工学府 H 棟（先端エネルギー理工学専攻棟）２階講義室
Lecture Room on 2F in H building
講演者：Mr. Z. Huang
Ecole Polytechnique Fédérale Lausanne
講演題目：Investigation of plasma turbulence and geodesic acoustic modes using
tangential phase-contrast imaging in the TCV tokamak
The anomalous transport caused by the plasma turbulence is one of the outstanding physics
issues in magnetic-confinement fusion research, due to the attendant degradation of energy
confinement and ultimately fusion reactivity. Experimental measurements of plasma
micro-turbulence, i.e., fine-scale, broadband fluctuations have thus become an essential need. A
tangential phase-contrast imaging (TPCI) diagnostic has been designed and installed on the
Tokamak à Configuration Variable (TCV) to measure line-integrated density fluctuations with high
sensitivity and temporal resolution; by employing a spatial filtering technique, radially localized
measurements can also be performed with excellent spatial resolution from the core to the edge
plasma, taking advantage of the flexibility of TCV regarding plasma shape and position. TPCI
measurements have been performed to study the dependence of density fluctuations on plasma
shape and radial position as well as collisionality. In particular, we sought to investigate the
improvement in energy confinement at negative edge triangularity in the core region where local
triangularity is vanishingly small. The measurements show a substantial reduction of the turbulence
amplitude from positive to negative triangularity, consistent with the experimental observation of
transport reduction in TCV and with non-linear gyrokinetic simulations. In addition, the geodesic
acoustic modes (GAM) have been characterized further on TCV through parametric studies of the
GAM frequency and amplitude. A transition between a frequency continuum and a
single-frequency global eigenmode was observed for the first time in a single discharge by varying
the edge safety factor. The GAM drive and damping were also investigated in a density ramp-up
with bi-spectral analysis.
問い合わせ先：[email protected]

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