Abstract
Simulations have been performed to investigate the impact of radial variation of neutral atoms (neutral puff) on the edge plasma of small size divertor tokamak. It was demonstrated that, the variation of neutral atoms (neutral puff) in edge plasma of small size divertor tokamak generates additional large radial electric field and large radial electric field shear near separatrix which can significantly influence global confinement by affecting the transition from low (L) to high (H) confinement. This simulation was performed by using B2SOLPS0.5.2D fluid transport code based on a reduced form of the transport form of transport equations. These transport equations are implemented in B2SOLPS0.5.2D fluid transport code and solved for the parameters of Small Size Divertor tokamak. The results of simulation by fluid transport B2SOLPS0.5.2D code can be summarized as follow: 1) The Plasma Parameters are significantly effect by neutral atoms puffing in the edge plasma of small size divertor tokamak; 2) Contrary to previous expectation [1] of the predominant role of neutral viscosity on toroidal flux, anomalous transport was found to be mainly effect on toroidal flux; 3) Puffing of gas (neutral) in the edge plasma of small size divertor tokamak produce strong ITB; 4) Puffing of gas (neutral) in the edge plasma of small size divertor increase plasma density especially in SOL through charge exchange and ionization processes; 5) Puffing of gas (neutral) in the edge plasma of small size divertor has significant effect on the distribution of plasma heat flux; 6) The radial electric field is affected by gas (neutral) puffing in the edge plasma of small size divertor; 7) Puffing of neutral (atoms) in the edge plasma of small size divertor tokamak produce large radial electric field shear which contribute to L-H transition; 8) The centrifugal effect has no influence on distribution of the radial profile of parallel (toroidal) velocity of edge plasma of small size divertor tokamak during gas (neutral) puffing; 9) The bootstrap current in edge plasma of small size divertor tokamak is significantly affected by gas (neutral) puffing.
Highlights
Neutral atoms in tokamak edge plasma can significantly influence global confinement by affecting the transition from low (L) to high (H) confinement
In the present paper modeling of the impact of gas puff on tokamak edge plasma is performed by means of the B2SOLPS0.5.2D fluid transport code for NBI shots for small size divertor tokamak
3) Additional radial electric field associated with ionization source generated by gas puff in edge plasma of small size divertor tokamak
Summary
Neutral atoms in tokamak edge plasma can significantly influence global confinement by affecting the transition from low (L) to high (H) confinement. The neutrals affect the ion dynamics through charge exchange (CX), and the neutral flux of toroidal angular momentum can modify or even determine the edge radial electric field and the plasma rotation [1]. Previous results suggest an external means for controlling toroidal flow and radial electric field at the edge that is being investigated on MAST [2,3]. In the present paper modeling of the impact of gas (neutral) puff on tokamak edge plasma is performed by means of the B2SOLPS0.5.2D fluid transport code for NBI shots for small size divertor tokamak. The impact of gas (neutral) puff on plasma parameters, plasma heat fluxes and radial electric field are investigated
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