Speaker
Description
Study of high-confinement mode (H- mode) of tokamak operation plays an important role to optimize conditions for fusion reactors. Many experimental techniques, including electrode biasing and resonant magnetic perturbations (RMP), have been developed to improve the plasma confinement, facilitating transition from low to high confinement mode (L-H transition) and to study the transition mechanism. The H-mode is characterized by a rapid increase in plasma density, in conjunction with a sudden drop in H alpha emissions, indicating an improvement in both particle and energy confinements. The Saskatchewan Torus-Modified (STOR-M) tokamak is a small tokamak with a major radius of 46 cm and minor radius of 12 cm. The operational parameters during the biasing experiments are B_t (toroidal magnetic field) ~ 0.7 T, I_p (plasma current) ~ 25 kA, V_l (loop voltage) ~ 3 V, n_e (average density) ~ 1×10^13 cm-3, T_e (average electron density) ~ 100 eV, and τ_E (global energy confinement time) ~ 2 ms. Hydrogen plasma is used for the experiment. On the (STOR-M) tokamak, the electrode biasing experiments have been carried out to induce a sheared electric field and suppress the turbulence induced transport. The electrode is placed at different radial locations and the biasing voltage and polarity can be varied between shots. Biasing experiments with rectangular AC waveforms have also been carried out in the STOR-M tokamak. The RMP experiments carried out in the STOR-M tokamak using the (l = 2, n = 1) helical coils carrying a static current pulse. The resonant interaction between the plasma and RMP suppresses magnetohydrodynamic (MHD) fluctuations and improves plasma confinement. The current work will focus on the studies of the correlations between different electrostatic and/or magnetic fluctuating signals measured with various diagnostic probes.
