Impurity Transport in a Quiescent Tokamak Plasma

Impurity Transport in a Quiescent Tokamak Plasma
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Release: 1975
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Short bursts of aluminum were injected into the Adiabatic Toroidal Compressor (ATC) Tokamak, and measured the time evolution of the radial distributions of highly ionized states of aluminum. The results are compared with a computer code describing neoclassical impurity diffusion and good agreement is found. (auth).

Orbit Effects on Impurity Transport in a Rotating Tokamak Plasma

Orbit Effects on Impurity Transport in a Rotating Tokamak Plasma
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Release: 1988
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Particle orbits in a rotating tokamak plasma are calculated from the equation of motion in the frame that rotates with the plasma. It is found that heavy particles in a rotating plasma can drift away from magnetic surfaces significantly faster with a higher bounce frequency, resulting in a diffusion coefficient much larger than that for a stationary plasma. Particle orbits near the surface of a rotating tokamak are also analyzed. Orbit effects indicate that more impurities can penetrate into a plasma rotating with counter-beam injection. Particle simulation is carried out with realistic experimental parameters and the results are in qualitative agreement with some experimental observations in the Tokamak Fusion Test Reactor (TFTR). 19 refs., 15 figs.

QUIESCENT DOUBLE BARRIER H-MODE PLASMAS IN THE DIII-D TOKAMAK.

QUIESCENT DOUBLE BARRIER H-MODE PLASMAS IN THE DIII-D TOKAMAK.
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Release: 2003
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High confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D[J.L. Luxon, et al., Plasma Phys. and Contr. Nucl. Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987) Vol. I, p. 159] this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation which is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 seconds or>25 energy confinement times[tau][sub E]), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved[beta][sub N] H[sub 89]= 7 for up to 5 times the[tau][sub E] of 150 ms. The[beta][sub N] H[sub 89] values of 7 substantially exceed the value of 4 routinely achieved in standard ELMing H-mode. The key factors in creating the quiescent H-mode operation are neutral beam injection in the direction opposite to the plasma current (counter injection) plus cryopumping to reduce the density. Density and impurity control in the quiescent H-mode is possible because of the presence of an edge magnetic hydrodynamic (MHD) oscillation, the edge harmonic oscillation, which enhances the edge particle transport while leaving the energy transport unaffected.