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(EX4/6) Confinement in TPE-RX Reversed Field Pinch

Y. Yagi¹⁾, T. Bolzonella²⁾, A. Canton²⁾, K. Hayase¹⁾, Y. Hirano¹⁾, S. Kiyama¹⁾, H. Koguchi¹⁾, Y. Maejima¹⁾, J.-A. Malmberg³⁾, H. Sakakita¹⁾, Y. Sato¹⁾, S. Sekine¹⁾, T. Shimada¹⁾, K. Sugisaki^1)
 
1) Electrotechnical Laboratory, Tsukuba 305-8568 Japan
²⁾ Consorzio RFX, Padua 35127 Italy
³⁾ Royal Institute of Technology, Stockholm 100 44 Sweden

Abstract.  Characteristics of the confinement properties of a reversed field pinch (RFP), the TPE-RX ( R/a = 1.72/0.45 m, R and a are major and minor radii), are presented for the plasma current, I_p of 0.2-0.4 MA. TPE-RX has been operational since 1998, and I_p = 0.5 MA and duration time of up to 0.1 s have been obtained separately. It is found that I_p/N (= 12×10^-14 Am, N is the line density) is higher than those of other RFPs and poloidal beta, $\beta_{\mathrm{p}}^{}$, and energy confinement time, $\tau_{\mathrm{E}}^{}$, are 5-10% and 0.5-1 ms, respectively, which are comparable with those of other RFPs of comparable sizes (RFX and MST). Pulsed poloidal current drive has recently been tested and the result has shown a twofold improvement of $\beta_{\mathrm{p}}^{}$ and $\tau_{\mathrm{E}}^{}$. The improvement is discussed in terms of the dynamic trajectories in the F - $\Theta$ plane, where F and $\Theta$ are reversal and pinch parameters, respectively. The global confinement properties are compared between the locked and nonlocked discharges, which yields a better understanding of the mode-locking phenomena in RFP plasmas.

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