Enhancement of localized ICRF heating and current drive in TFTR D-T plasmas

Theoretical advantages have led to an increased importance of the modification and sustainment of pressure and magnetic shear profiles in plasmas. We have demonstrated electron heating and current drive in TFTR plasmas with the existing 43/63.6 MHz ICRF system, both via the fast wave and via mode conversion of the fast wave to an ion Bernstein wave. In order to achieve both on and off-axis mode conversion in a pure D-T plasma, we have changed the operating frequency of two of our transmitters and antennas to 30 MHz and improved the launched directional wave spectrum. As a second step, two new four-strap fast wave antennas have been installed, and a new four-strap direct-launch IBW antenna has been added as well. This reconfiguration and the resulting operating characteristics of the TFTR ICRF system in a variety of discharges will be presented.