First experimental results of the PAM LHCD launcher at 2.45 GHz on EAST

This paper presents the first results of a passive active multijunction (PAM) launcher at 2.45 GHz during the lower hybrid current drive (LHCD) experiments on EAST. Good coupling performance with a power reflection coefficient (RC) ∼3% has been achieved at the plasma–antenna distance up to ∼11 cm in L-mode edge plasmas without local gas puffing near the PAM launcher. Reliable power coupling of this PAM during the edge perturbations induced by type I edge localized modes (ELMs) has been successfully demonstrated. Compared with the old full active multijunction (FAM) launcher, the new PAM can be placed ∼2 cm further away from the plasma in normal operations, which is in good agreement with the previous prediction (Li et al 2019 Fusion Eng. Des.147 111 250), by the linear wave–plasma coupling code ALOHA (Hillairet et al 2010 Nucl. Fusion50 125 010). The flexibility of the power spectrum by changing the phase difference between adjacent modules was validated and ray-tracing/Fokker–Planck simulations can reproduce the experimental features. The achievable power handling is as high as 25 MW m−2, although with a shot pulse length of ∼10 s. The first experiment successfully demonstrated the coupling performance of a PAM launcher at low density and this launcher construction provides helpful engineering experience for the 4.6 GHz PAM development in the near future on EAST.