Abstract
The DIII-D ECH complex is being upgraded with three new depressed collector gyrotrons. The performance of the existing system has been very good. As more gyrotrons having higher power are added to the system, diagnostics of gyrotron operation, optimization of the performance and qualification of components for higher power become more important. A new FPGA-based gyrotron control system is being installed, additional capabilities for rapid real time variation of the rf injection angles by the DIII-D Plasma Control System are being tested and infrastructure enhancements are being completed. Longer term plans continue to include ECH as a major component in the DIII-D heating and current drive capabilities.
Highlights
The DIII-D ECH complex is being upgraded with three new depressed collector gyrotrons
As more gyrotrons having higher power are added to the system, diagnostics of gyrotron operation, optimization of the performance and qualification of components for higher power become more important
A new FPGA-based gyrotron control system is being installed, additional capabilities for rapid real time variation of the rf injection angles by the DIII-D Plasma Control System are being tested and infrastructure enhancements are being completed
Summary
The Plasma Control System [8] on DIII-D provides real time control of the many parameters which affect the time dependence of the plasma shape, performance and position in the vacuum vessel. The PCS is being configured to be able to change the angles of the ECH launcher mirrors to steer the rf beams independently in the poloidal direction in response to pre-programmed commands or the need to mitigate plasma instabilities requiring real time command and response. The edge of the port box is traced and drawn on the ir video monitor screen for a reference This test provides a visual evaluation of the quality of the Gaussian beam in the vacuum vessel when the beams are away from the tiles. This capability will be used for precise control of MHD instabilities, transport studies and to enable two or more experiments employing different ECH steering on a single DIII-D plasma shot to be performed. Real time toroidal steering and polarizer variation are not being implemented, since current drive efficiency is relatively insensitive to the toroidal angle and most motion does not appreciably change the desired polarization
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