STATUS OF THE DIII-D 110 GHZ ECH SYSTEM

The DIII-D program is presently commissioning the first MW gyrotron of a planned 3 MW, 110 GHz electron cyclotron heating (ECH) system for o ff-axis electron heating and current drive. Advanced tokamak (AT) rese arch in DIII-D and other tokamaks requires the ability to control the current density profile. ECH offers the ability to localize the heatin g and driven current in a controllable manner and is not dependent upo n, the local plasma conditions, so it appears to be an ideal tool for AT research. The planned rf sources for the DIII-D system are 1 MW sta te-of-the-art internal mode-converter gyrotrons, with one gyrotron bei ng manufactured by GYCOM, a Russian company, and two gyrotrons being m anufactured by CPI (formerly Varian). The GYCOM gyrotron has been test ed at the factory to 960 kW, 2 seconds and has been shipped to GA wher e it is now undergoing initial checkout and testing. The first CPI gyr otron has been assembled and factory tested to 530 kW, 2 seconds and 3 50 kW, 10 seconds. Both the Gycom and CPI gyrotrons are limited in pul se length at full power by thermal limits on the output window. The se cond CPI gyrotron is expected to be ready for testing in April 1996.