Recent activities on SST-1 and ADITYA-U tokamaks

The successful operation of superconducting tokamaks is very challenging because of limitations arising out of a complex geometry, configuration and construction. The slow penetration of loop voltage because a continuous plasma chamber requires low loop voltage plasma initiation. Apart from these operational challenges, SST1 also has technical issues related to cooling down of the superconducting poloidal field (PF) coils, for obtaining advanced plasma operation and control. Furthermore, limits are imposed on the loop voltage by magnet power supplies and PF coil insulation. To improve our understanding of these issues, operations in SST-1 have been attempted with low loop voltages and will be discussed in this paper. It is envisaged that designing and carrying out experiments in SST1, to understand above issues, may be very complex, time consuming and may not be feasible due to complexities in SST1 machine operational scenario. Hence Aditya machine upgradation was initiated with the understanding that solution to some of these problems may be obtained through experiments specially designed for this purpose in ADITYA-U, in parallel. Thus some of these experiments are also being planned to carry out in tokamak ADITYA-U, in particular, non-inductive current drive using lower hybrid waves, employing passive active multi-junction (PAM) antenna. The performance of the lower hybrid waves launched by the grill antenna is presented and the need for PAM antenna is presented. The design of the PAM antenna for ADITYA-U machine is also discussed. © 2019 The Japan Society of Plasma.