1 - Nuclear Sciences and Applications - IAEA

612 BATCHELOR et al.
resolves this problem and gives an approximately constant field in the Faraday shield gap as expected.
The proper treatment of Bp has been addressed by development of a new 2D full-wave code,
HYPERION, which employs poloidal and toroidal mode expansion and straight field line coordinates.
This code also retains E|, includes the toroidal terms arising in the wave equation, and uses realistic
tokamak equilibria calculated with the RSTEQ code. Results are in excellent agreement with the ORION
code in the cylindrical limit and show that significant differences occur when the aspect ratio is ~3.
The presence of Bp results in a nonlocal plasma response to the wave fields and has a large effect on
the relative amounts of mode conversion and dissipation in large devices. A slab analysis has been performed
in which the wave perturbed current is found by boundary layer analysis of the Vlasov equation
and the resulting fourth-order integro-differential equation is solved numerically. Two cases of practical
interest are studied: minority fundamental resonance and second harmonic resonance. Reciprocity relations
are found and it is shown that in many cases conversion to Bernstein mode is greatly reduced while
absorption is increased as compared with the case of perpendicular stratification. For the treatment of
mode conversion in perpendicularly stratified plasmas, reduced-order analytic descriptions of coupled
mod^ equations have been developed which yield closed-form expressions for mode conversion in the
presence of kinetic dissipation. Results are presented for the Compact Ignition Tokamak parameters.
1. TWO-DIMENSIONAL, FULL-WAVE CALCULATIONS OF ICRF
FRINGING FIELDS NEAR THE FARADAY SCREEN
One of the major issues in theoretical modeling of ICRF experiments
is the effect of fringing fields on impurity generations near the Faraday
screen. In the edge plasma and antenna regions, densities are low enough
that parallel electric fields can be significant. Thus, the usual fast-wave
assumption E\\ ~ 0 is not appropriate and the complete wave equation
including E\\ must be solved. Here, we consider two alternate numerical
approaches to this problem. One solves Maxwell's equation directly in
terms of the electric field E:
-V x V x E+—Z-E= -iwfj,0Jexl (1)
V.S-£ = ^ (2)
en
We solve the wave equation (1) by inverting the VxVx£ operator directly.
Since the divergence of Eq. (1) gives Eq. (2), which is Poisson's equation,
the solution to (1) should in principle include electrostatic effects. The
second approach introduces the appropriate electromagnetic potentials A
and with the coulomb gauge V • A — 0. Equations (1) and (2) then
become
A + ^ (S • V