Modification on the gyrokinetic quasi-neutrality condition due to large flow

Miyato, Naoaki; Scott, B. D.*

Proceedings of 37th European Physical Society Conference on Plasma Physics (EPS 2010) (CD-ROM), 4 Pages, 2010/06

http://ocs.ciemat.es/EPS2010PAP/pdf/P1.1070.pdf

Reduced kinetic models such as gyrokinetic models are constructed by phase space transformation from particle phase space to guiding-centre phase space. In the reduced quasi-neutrality condition or the Poisson equation for electrostatic potential, particle density should be represented in terms of guiding-centre things. It is called push-forward representation of particle density. Recently a reduced kinetic model with large flow was derived by modifying the standard guiding-centre transformation. The model can be regarded as a natural extension of the standard model to the large flow regime because the symplectic part in the guiding-centre phase space Lagrangian is the same as the standard one formally. The push-forward representation of particle density or the reduced quasi-neutrality condition in the transonic case is derived by the variational method. It is found that corrections due to the flow appear in the polarisation density.

Measurement of type-I ELM pulse propagation in SOL through BES use of MSE diagnostics in JT-60U and impact of ELM on MSE diagnostics

Suzuki, Takahiro; Oyama, Naoyuki; Asakura, Nobuyuki; Fujita, Takaaki

Proceedings of 37th European Physical Society Conference on Plasma Physics (EPS 2010) (CD-ROM), 4 Pages, 2010/06

http://ocs.ciemat.es/EPS2010PAP/pdf/D4.516.pdf

Since transient heat and particle loads by the type-I ELMs are significantly high for the plasma facing components of the fusion reactor, understanding propagation of plasma ejected by ELMs (ELM pulse) in SOL is important. Increase in the SOL plasma density due to the ELM pulse has been measured through the increase in beam emission (BE) at various radial locations in SOL near equatorial plane, using MSE diagnostics as beam emission spectroscopy (BES) diagnostics. From the temporal delay of the increase of BE as a function of major radius in the SOL, radial velocity of the ELM pulse propagation has been evaluated as 0.8-1.8 km/s. In accurately evaluating the velocity, elimination of background (BG) light from the BES signal is found essential since the delay of the net BE is veiled by the BG light that increases in synchronous to the ELM pulse. The intermittent increase in the BG light synchronized with ELMs has been observed in MSE channels viewing not only the SOL but also the main plasma. Since this BG light affects the magnetic pitch angle measurement by MSE diagnostics as was reported in JET, the impact of the intermittent BG light by ELMs on MSE diagnostics has been investigated numerically. When intermittent BG light by ELMs mixes with PEM modulation for MSE diagnostics, broadband spectrum of the impulse-like BG light disturbs the spectrum intensities, even if the BG light is not polarized. Numerical simulation shows that error induced by ELMs piles up if ELM frequency is higher than , where is time constant of lock-in amplifier detecting PEM modulation, and then, the error remains even between ELMs.

TSC modelling approach to mimicking the halo current in ASDEX upgrade disruptive discharges

Nakamura, Yukiharu*; Pautasso, G.*; Sugihara, Masayoshi*; Miyamoto, Seiji; Toshimitsu, Shinichi; Yoshino, Ryuji; ASDEX Upgrade Team*

Proceedings of 37th European Physical Society Conference on Plasma Physics (EPS 2010) (CD-ROM), 4 Pages, 2010/06

http://ocs.ciemat.es/EPS2010PAP/pdf/P2.184.pdf

Of particular importance for the assessment of electromagnetic loads on vacuum vessel and in-vessel components of ITER is the halo current which achieves a maximum during VDEs (VDE: vertical displacement event). However, halo current models have a limited development so far with a few exceptions such as a validation study of the JT-60U halo current modelling using the DINA code. Recently, several experimental groups have prepared systematic halo current data, and further model development and validation with these data need to be performed using an axisymmetric, two-dimensional, free boundary code, TSC. To enhance an understanding of the maximum halo current and large vertical shifts, a reference discharge was selected from those included in the ASDEX upgrade disruption database. Systematic TSC simulations were performed to mimic the observation of a slow VDE of hot plasma and an ensuing fast downward-going VDE during a subsequent plasma current quench. Careful parameter adjustment of the temperature and width of the halo region was examined to mimic measurements of the halo current. A spontaneous, downward-going VDE was reproduced accurately in a manner that closely resembled experimental observations.

Assessment of integrated physics design of the JT-60SA plasmas

Ide, Shunsuke; Kamada, Yutaka; Lackner, K.*; Bolzonella, T.*; Fujita, Takaaki; JT-60SA Team

no journal, ,