Theory Weekly Highlights for July 2004

June 25, 2004

Ideal calculations for a sequence of fully bootstrapped equilibria obtained by scaling the vacuum toroidal field showed instability with no wall but stability with the DIII-D wall and with considerable structure in the growth rates as functions of q0, qmin, and qedge. Minima and maxima in the growth rates do not correspond to integer values of any of q0, qmin, and qedge. The perturbed flux on the outer, low field side boundary is also remarkably insensitive to these parameters over a wide range (5 5 < q0 < 12.05), including the successive maxima and minima in the growth rate. The outboard mode structure is insensitive to the qedge value even though the poloidal m = n* qedge harmonic (n = 1) dominates at the boundary, and is even insensitive to he presence or absence of nearby integer qedge values where there is a strong peeling component. This result implies that active feedback control of the associated RWM should also be quite insensitive to these parameters, which may simplify feedback schemes.

June 18, 2004

Based on the assumption that the angular momentum confinement time is the same as the energy confinement time, a formula has been devised for the toroidal rotation frequency expected in ITER. This projects a 2.4 kHz rotation frequency for ITER, given an efficiency of 50% for generating toroidal momentum from a 1 MeV neutral beam. The method also predicts a 21 kHz rotation rate for DIII-D, which is of the order that is generally observed. This should be extremely useful in ITER design work, especially for Resistive Wall Mode stabilization.

June 11, 2004

Recent modeling has shown that, given sufficient pulse length, a steady state ITER configuration is achievable assuming the GLF23 energy and toroidal rotation transport model and fixed density profiles. The simulations were based on current 9-MA discharge ITER design parameters and used the ONETWO transport code, together with ECH and ECCD calculations from TORAY-GA and fast wave ICH and ICCD from CURRAY. The steady state configuration features a constant E, with essentially 100% non-inductive current drive, and is maintained by a total of 73 MW of input power, consisting of 33 MW of 1 MeV NNBI, 20 MW of fast wave and 20 MW of ECH. Optimization of the non-inductive current fraction and fusion gain assuming the initial ITER hardware capabilities is underway.

These highlights are reports of research work in progress and are accordingly subject to change or modification