| Plasma response to RF waves to arbitrary magnetic geometries |
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The physics of RF waves in plasmas is of great interest in the field of fusion physics. The design of heating, current drive, and profile control systems are dependent upon a good understanding of the propagation and absorption of these waves. Previous treatments of this problem assumed that particles in the plasma interacted with waves in the presence of a straight magnetic field lines with strength gradients parallel to the field lines. In a real fusion reactor field lines are curved, and the gradients in the field strength can be in
arbitrary
directions. To incorporate these additional physical effects we have recalculated the plasma response function and plasma conductivity using the method of characteristics.
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| Figure 1. The plasma response function, Z, as a function of frequency away from
resonance(xi). The results of the previous theory with parallel
gradients in a straight field (black), and with our new theory including
curvature as well as parallel gradients (red) are compared. |
This method involves integrating the effect of the wave on a particle following an unperturbed trajectory. In contrast to previous treatments of the problem we have constructed our characteristic trajectories to include curvature and gradient drifts that were previously omitted. We have also incorporated particle-particle collision in a more comprehensive manner then previous treatments. We have found that adding these new geometric effects changes the plasma response function in important ways, which we believe will change the predictions for wave propagation and absorption.
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