A two-dimensional, computationally efficient numerical model is developed to study power deposition in high-density inductively coupled plasma sources. Calculations include both inductive coupling, caused by plasma response to external coil currents, and capacitive coupling, caused by plasma response to external voltages on the coils and wafer. Variation in current along the induction coil is determined self-consistently from the integral constraint of charge conservation. Sheath phenomena are incorporated through previously published analytic models. The system behavior is analogous in some respects to that of a transmission line. Comparison with measurement suggests that this model provides a good description of self-consistent coil response when the electric field exhibits less than a quarter wavelength per coil turn.
Bootstrap currents in the low collisionality regime in nonaxisymmetric toroidal plasmas are calculated analytically using a model drift kinetic equation. The results obtained using the analytic expression are compared with those calculated from the numerical solutions of the drift kinetic equation. Qualitatively and quantitively, the results are in reasonable agreement.
Location-awareness is an important requirement for many mobile wireless applications today. When GPS is not applicable because of the required precision and/or the resource constraints on the hardware platform, radio interferometric ranging may offer an alternative. In this paper, we present a technique that enables the precise tracking of multiple wireless nodes simultaneously. It relies on multiple infrastructure nodes deployed at known locations measuring the position of tracked mobile nodes using radio interferometry. In addition to location information, the approach also provides node velocity estimates by measuring the Doppler shift of the interference signal. The performance of the technique is evaluated using a prototype implementation on mote-class wireless sensor nodes. Finally, a possible application scenario of dirty bomb detection in a football stadium is briefly described.
The poloidal coil system of a stellarator can be used to modify the ‖B‖ spectrum and, as a consequence, change the magnitude of the bootstrap current. The addition of a small l=1 field component to a stellarator field can cancel or reverse the direction of the bootstrap current. It is shown that currentless operation in the collisionless regime is not impaired by bootstrap current, because the effects of bootstrap current can be eliminated by an appropriate external coil system. The advanced toroidal facility (ATF) [Fusion Technol. 10, 179 (1986)] can be used to test some of these results.
Orbits in an asymmetric toroidal magnetic field are studied for the case in which the local variation of the field strength due to ripple is rapid compared with that due to toroidicity. In this case, to lowest order the poloidal variables are constant and particles move primarily in the toroidal direction. Invariants and averaged equations of motion for the locally passing and locally trapped particles are derived based on this approximation. The equations imply that transitions between the locally trapped and locally passing states occur. The probabilities for these transitions are calculated.
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