Passive Active Multijunction Launcher Research Articles

ITER-like PAM launcher for Tore Supra's LHCD system

Abstract In the frame of the Tore Supra Composants d’Injection de Matiere et d’Energie Stationnaire (CIMES) Project, consisting in particle fuelling via a pellet injector and in energy powering using Lower-Hybrid Current Drive (LHCD) for pulses lasting 1000 s, complemented by the transmitter refurbishing, a new launcher, based on the Passive-Active Multijunction (PAM) concept already proposed for ITER, has been developed and is currently under realisation. It was designed for a power injection capability of 2.7 MW CW at 3.7 GHz, a power density of 25 MW/m 2 , to radiate a power spectrum peaked at N // = 1.7 with a maximum power directivity near the electron cut-off density and with very good coupling properties on a wide range of electron densities. In this paper, an overall description of the antenna as well as the foreseen manufacturing and assembling processes are given, followed by the results from studies and optimisations of its RF components, by a stress analysis of its thermo-mechanical behaviour, taking into account the plasma radiated flux at the mouth and the RF losses, and complemented with additional mechanical stresses due to the combined action of the eddy current induced in the launcher by disruptions and the residual toroidal magnetic field.

The test of a PAM launcher on FTU: The first step toward the LHCD launcher for ITER

The 20 MW, 5 GHz, LHCD system for ITER aims mainly at controlling the q-profiles in partially (hybrid regime at IP = 12 MA) and fully non-inductive steady-state operation (IP = 9 MA). In the last few years several European associations have given their contribution to the solution of many prominent problems on the road to the design of an efficient and reliable system. LH coupling has been achieved on JET in physics scenarios relevant for ITER, while the reliability of the LH for long pulse operation has been ascertained on Tore Supra. A downscaled prototype of the Passive Active Multijunction (PAM) launcher presently proposed for ITER, has successfully demonstrated on FTU its good coupling characteristics, power handling capability and current drive efficiency. An ITER relevant launcher, based on the PAM concept is presently under construction to be installed on TORE SUPRA to investigate the technological solutions (materials, cooling, etc.) envisaged for this launcher.

The PAM launcher for FTU: results of the preliminary tests

The Passive active multi-junction (PAM) launcher is a robust coupling structure, able to withstand the strong thermal loads and the electromechanical stresses of ITER-like tokamaks. In the frame of a collaboration between ENEA, Frascati and CEA, Cadarache, a PAM antenna has been designed and built to validate on FTU the concept of this launcher. All the technological solutions of an ITER-like launcher will be tested in a full rated experiment to be performed, possibly, on Tore Supra. This paper reports the results of the low power measurements of the microwave characteristics of the PAM for FTU.