Recent Colloquium

Role of neutral gas molecules in Scrape-off Layer (SOL) region of tokamak plasma is important as it is expected to modify the plasma turbulence. Two-dimensional (2D) model has been used that consists of electron continuity, molecular ion continuity, quasi-neutrality, electron energy and neutral molecular gas continuity equations in the presence of the electron impact molecular ionizations and other non-ionizing collisions. The growth rate obtained from these equations has been presented using linear theory. It is observed that the growth rate increases with the neutral gas ionization coefficients. The nonlinear equations are solved numerically in the presence and absence of the neutral gas molecules. Radial profiles of plasma density, electron temperature, and electric field have been obtained. It is found that the neutral gas reduces electric fields. More significant reduction of the poloidal electric field has been found by the neutral gas. Time series obtained from the numerical data have been analyzed. A strong decrease of fluctuation of the plasma density, electron temperature, and potential has been found at the outer region the SOL plasma in the presence of the gas molecules.

Nirmal Kumar Bisai had completed B.Sc and M.Sc in physics from the University of Calcutta. He joined Institute for Plasma Research (IPR) as a scientist in 1995. Theoretical and numerical work on fusion plasmas specifically on plasma turbulence in tokamak boundary region are his main working area. He obtained PhD from the University of Gujarat in plasma physics. He was a member of “Integrated Modeling Expert Group (IMEG)” in ITER, France during 2009-2013. He became a member of “Scrape-off Layer & Divertor” topical group for the International Tokamak Physics Activity (ITPA) in 2009 and in 2013 he also became a member of “Pedestal and Edge Physics Topical Group” for the ITPA. His theoretical/simulation work on plasma blob formation in tokamak plasma had been well recognized internationally.