High-density LH and EC current drive
Abstract
This work reports results on LH (f = 8 GHz, 1.8 MW) current drive experiments in the FTU tokamak in the range of density from 0.5 - 1.0×10^20m-3, BT = 7.2 T, Ip = 0.5 MA relevant for reactor regimes. In this condition, with 1.8 MW of LH power, the fraction of the current driven by the wave ranges from 100% to 75% with increasing in Te ranging from 4 to 2 KeV and complete stabilization of sawtooth activity. The increase in collisionality at these densities leads to a significant transfer of energy from electrons to ions, as shown from Ti increasing up to 20%. The dependence of current drive efficiency on the launched N_|| spectrum from the grill has been investigated. Experiments of combined launch of LH and EC waves (f= 140 GHz, 0.8 MW) are reported. The down-shifted scheme is used where the EC wave resonates on the fast-electron tail generated by LH. EC power absorption up to 80% is measured at BT = 7.2 T (cold resonance at 5 T outside the plasma), an increment in Te up to 1 KeV and a drop in loop voltage are also obtained. The EC power absorption is well related to the fast electron tail density and is compared with a linear model of suprathermal interaction.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 2002
- Bibcode:
- 2002APS..DPPRP1009P