O. Mitarai, A. Sagara, N. Ashikawa, R. Sakamoto, M. Yoshinuma, M. Goto, T. Morisaki, T. Masuzaki, K. Ida, S. Morita, M. Osakabe, K. Tanaka, K. Nagaoka, N. Ohyabu, A. Komori, and O. Motojima


The low temperature and high density ignition in the helical reactor FFHR2m based on LHD experiments

Date of publication:

Oct. 2008

Key words:

21 IAEA Fusion Energy Conference, FT/P3-19


New control method of the unstable operating point in the helical reactor FFHR makes the ignition study on the high density and low temperature operation possible. It is a proportional-integration-derivative (PID) control of the fueling with the error of the fusion power of e(Pf)= -(Pfo-pf), which can stabilize the unstable operating point. Here Pfo(t) is the fusion power set value and Pf(t) is the measured fusion power. Although the large parameter variation would lose its control due to the inherently unstable nature, it is still possible to control the ignited operation with pellet injection if the pellet size is smaller than 16 mm. As sensitivity analysis on other parameters makes the helium ash confinement time ratio crucial, preliminary experimental results on helium ash measurement in LHD are also presented. We finally discovered that major plasma parameters for 1 .9 GW fusion power are close to plasma parameters independently achieved in LHD experiments.

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