|Title||Experimental studies towards long pulse steady state operation in LHD|
|Publication Type||Journal Article|
|Year of Publication||2001|
|Authors||N. Noda, Y. Nakamura, Y. Takeiri, T. Mutoh, R. Kumazawa, M. Sato, K. Kawahata, S. Yamada, T. Shimozuma, Y. Oka et al.|
|ISBN Number||0029-5515; 1741-4326|
In the Large Helical Device, stable discharges lasting longer than one minute have been obtained using the complete heating scheme, including ECH. The plasma is sustained with NBI or ICRF of 0.5-1 MW. The central plasma temperature is higher than 1.5 keV with a density of (1-2) x 10(19) m(-3) maintained until the end of the pulse. Full installation of the carbon divertor has contributed to this achievement. This provides a sufficient basis for physics and technology studies for the next campaign. Long pulse operation opens new possibilities in diagnostics and in physics studies. Higher accuracy and reliability are obtained with a diagnostics parameter scan, longer integration of signals or two dimensional measurement. The mechanism of a slow oscillation called 'breathing' is discussed. Hydrogen recycling analysis has been carried out and preliminary results have been obtained. On the basis of these results, the future programme is divided into two categories: (i) physics and technology experiments utilizing long pulse discharges lasting up to 5 minutes, and (ii) extension of the pulse length up to one hour.
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