Low power testing of losses in components for the ITER ECH transmission lines

The transmission lines (TLs) for ITER electron cyclotron heating require extremely low losses, since the 24 MW of power generated by the 170 GHz gyrotrons should be delivered to the plasma with an efficiency of 83% or more. We are developing cold-test techniques to precisely measure the losses in the TL components for ITER, before installation. Experimental results on the measurement of the loss in some TL systems with coherent and incoherent techniques are presented and compared. We report a preliminary measurement of loss in the prototype TL components for the ITER 170 GHz transmission line.