Experiment with the pam launcher for FTU

Abstract

Systems working in the lower hybrid range of frequencies have experimentally demonstrated the highest off-axis current drive efficiency. A lower hybrid system is therefore the best candidate for off-axis current drive (CD) on ITER, where it could also be efficiently used for production and control of advanced scenarios. The severe environment of ITER requires a robust and efficiently cooled launcher and an improved coupling control capability. In this frame the passive active multi-junction (PAM) launcher, proposed by C.E.A. Cadarache, seems to be a preferred candidate. To test the real performances of this, still conceptual, launcher, a formal collaboration has been undertaken between ENEA, Frascati, and CEA, Cadarache. The first step of this collaboration is the validation of the PAM concept on the Frascati Tokamak Upgrade (FTU), where the coupling characteristics, the current drive efficiency, the power handling capability and directivity of a specifically designed launcher will be verified. The test on FTU is ITER relevant due to the high plasma density and the high magnetic field of this machine. In addition the coupling performances of this new launcher are directly comparable with those of a conventional grill positioned in the same toroidal position, but in a different port of FTU.