High density plasma production using m= +I and m=-1 helicon waves is studied. Characteristics of cylindrical helicon waves including effects of a vacuum gap between the plasma and the conducting wall and of a non-uniform separately excited by a helical antenna, and the dependences of plasma density and antenna loading resistance on RF power are shown to be different for these modes.
The stability of the radiation front in the scrape-off layer (SOL) of a tokamak is studied with a one-dimensional fluid code; the time-dependent transport equations are solved in the direction parallel to a magnetic field line. As the energy from the core into the SOL plasma is reduced, stable attached solutions change into stable detached solutions. Whenever such stable detached states are attained, the strong radiation front is in contact with or at a small distance from the divertor target. When the input energy is decreased further and total losses become larger than the input power, the radiation front starts to move towards the X-point, cooling the SOL plasma. In such a case, no solutions for the radiation front resting in the divertor channel are observed in our parameter space. This qualitatively corresponds to the results of tokamak divertor experiments which show the movement of the radiation front.
A model of 3He enrichments, which was proposed recently, is extended to study enhancements of heavy ions in high-energy particles. With weak currents parallel to the ambient magnetic field, oblique ion-acoustic waves and H cyclotron waves can become unstable. The former can have much greater growth rates at frequencies co ~ ft3He than at w ~ fhi~ near the marginal states of instabilities. The latter can be unstable at w ~ f~3He for a wide region of plasma parameters. Thus they could cause 3He enrichments through cyclotron resonances. At the same time, these waves can resonate with first or higher harmonics of cyclotron frequencies of many other ions. We investigate these resonant ions for several cases of plasma temperature. This model predicts enhancements of heavy elements and of neutron-rich isotopes at T ~ 10 MK. It shows heavy ion enhancements also at T ~ 4 MK. Clear differences between these two temperatures, however, can be seen in charge states of ions. At T ~ 2 MK, light ions as well as heavy ions can have cyclotron resonances with these waves, which suggests that such low temperatures are excluded.
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