Development of gas puffing system for LHCD experiment in Aditya tokamak

Lower hybrid (LH) wave coupling experiments have been successfully carried out in Aditya tokamak using 120 kW, pulsed LHCD system based at 3.7 GHz. To enhance the coupling of LH waves in the edge plasma region, an especially designed gas puffing system is developed to inject Hydrogen gas from the electron side of the grill antenna. The developed new gas puffing system consists of a multi-hole gas injection manifold with precisely fabricated holes. The dimensions of the manifold are determined so as to spread the gas uniformly in front of antenna. We achieved precise control of neutral gas injection near the antenna by this new gas puffing system of LHCD as observed by the images taken by fast camera. The gas puff using the manifold near the LH antenna led to considerable reduction in the reflection co-efficient of LH power indicating enhance absorption in plasma. The number of particles injection through gas puffing system has been estimated to figure out the optimum LH power coupling in Aditya tokamak. This paper presents detail of the developed gas puffing system for LHCD experiments and its implication on LHCD experiments. (author)