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The Electron Cyclotron Resonant Heating System on the DIII-D Tokamak

John Lohr, Y. A. Gorelov, K. Kajiwara, Dan Ponce, R. W. Callis, J. L. Doane, R. L. Ellis, H. J. Grunloh, C. P. Moeller, J. Peavey, R. Prater, J. F. Tooker

Fusion Science and Technology / Volume 48 / Number 2 / October 2005 / Pages 1226-1237

Technical Paper / DIII-D Tokamak - Technologies for Next-Step Devices /

In the DIII-D electron heating and current drive installation, up to six gyrotron microwave generators in the 1-MW class at pulse lengths up to 5 s have been operated simultaneously. The frequency for all the gyrotrons is 110 GHz, corresponding to the second harmonic of the electron gyrofrequency at 2 T. The peak generated power has been >4 MW with peak injected power slightly greater than 3 MW. The radio frequency (rf) generators are located remotely and are connected to the tokamak by up to 100 m of evacuated circular corrugated waveguide carrying the HE1,1 mode with overall transmission efficiency, including coupling to the waveguide, of up to 75%. Ancillary equipment for polarization control, beam switching, power monitoring, control of launch direction, and system protection has been developed.

The system has been used to support a wide variety of physics experiments, including control of magnetohydrodynamic modes, current density profile modifications, basic plasma heating and current drive, transport studies, and rf-assisted start-up. The gyrotron complex is being upgraded by the acquisition of additional tubes with 5- to 10-s pulse length capability.

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