EFFECT OF LOCALISED ELECTRON CYCLOTRON HEATING ON ENERGY CONFINEMENT AND MHD IN TCV

Within the range of plasma shapes and plasma currents investigated, the electron confinement time, tau_Ee, increases with safety factor, density and negative triangularity similar to the Ohmic heating case. There is little dependence of tau_Ee on the heating location provided power deposition occurs inside the q=1 surface; as power deposition moves out of the inversion surface, tau_Ee decreases. The power-induced energy confinement degradation exponent (tau_Ee~PaP) is as usual: alpha_P ~-0.5. As a general trend, central relaxations decrease in amplitude with increasing qa, P_EC, or negative delta, in a situation where the confinement time increases.


Published in:
europhysics conferences abstracts ECA, 1170
Presented at:
25th EPS & ICPP, Praghe, July 1998
Year:
1998
Keywords:
Note:
Excerpt: Plasma shape: triangularity The study of confinement with triangularity was done with medium qa, qa=3.5, at 500kW. The power was also deposited close to the inversion surface. Both ECRH and ohmic cases are shown in Fig. 6. As with ohmic heating, confinement improves with increasing negative triangularity during ECRH. Note that from this scan, the improvement of confinement with ECRH appears less than with purely ohmic heating. The real trend however is probably more favourable with negative triangularity than shown here, since power deposition occurred inside r_inv for delta>0 and outside r_inv for delta<0 (recall Fig. 2b).
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