12 research outputs found
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Numerical simulation of the Beta II experiment
The transport code FRT which is a 1-1/2-D transport-equilibrium code for an axisymmetric plasma was used to simulate the decay of the plasma and magnetic fields of the Beta II experiment. A comparison is made between the experimentally determined decay times for the magnetic fields and particle confinement times and the computed decay times. It is found that 1% oxygen impurity is enough to clamp the electron temperature below the radiation barrier, which is in agreement with the experiment
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Obtaining gigaflop performance from particle simulation of plasmas
In the numerical simulation of plasma phenomena there are two fundamental approaches that are generally followed. In the continuum approach one models the evolution of the fluid moment equations derived from the appropriate Boltzmann equation of the plasma. Alternatively, in the particle approach a large group of simulated charged particles are moved according to the self-consistent electromagnetic fields which partly depend on the charge and current densities of these same particles. Although the particle simulation method has been traditionally the more expensive of the two, it is much more capable of giving adequate account of many important kinetic phenomena. With the advent of the vector multiprocessor supercomputers, such as the Cray-2 or Cray Y-MP, we have learned to adapt particle simulation codes to exploit the parallel features of these machines. Yet, in spite of such developments, the particle simulation codes have remained much slower than the maximum machine speeds. We have investigated new techniques that further optimize these methods to bring the speeds of these particle simulations into the gigaflop range. Recent progress in this area suggests that the use of particle simulation methods will become competitive with the alternative fluid models especially when it is realized that gigaflop performance makes them much more affordable. 2 refs., 3 tabs