An efficient method is given for self-consistent reconstruction of the tokamak current profiles and their associated magnetic topology using the magnetohydrodynamic (MHD) equilibrium constraint from external magnetic measurements, kinetic profile measurements, internal poloidal magnetic field measurements, and topological information from soft X-ray (SXR) measurements. Illustrative examples for beam heated H-mode divertor discharges in the DIII-D tokamak are presented, using the experimentally measured kinetic profile information and external magnetic data from the existing diagnostics. Comparative reconstructions of the current profile using various combinations of diagnostics are given. Also presented is an alternative magnetic analysis method in which the MHD equilibrium is reconstructed using external magnetic data and a constraint on the edge pressure gradient. The results of a sensitivity study are given which show that the axial safety factor q(0) can be more accurately determined when additional information from internal poloidal magnetic measurements is used in conjunction with the external magnetic, kinetic and SXR topological data.

It is shown that the theoretical predictions and experimental observations of toroidicity-induced AlfvCn eigenmodes (TAE's) are now in good agreement, with particularly detailed agreement in the mode frequencies. Calculations of the driving and damping rates predict the importance of continuum damping for low toroidal mode numbers and this is confirmed experimentally. However, theoretical calculations in finite+?, shaped discharges predict the existence of other global AlfvCn modes, in particular the ellipticity-induced AlfvCn eigenmode (EAE) and a new mode, the beta-induced Alfvtn eigenmode (BAE). The BAE mode is calculated to be in or below the same frequency range as the TAE mode and may contribute to the experimental observations at high fl. Experimental evidence and complementary analyses are presented confirming the presence of the EAE mode at higher frequencies.

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Intense axisymmetric oscillations driven by suprathermal ions injected in the direction counter to the toroidal plasma current are observed in the DIII-D tokamak. The modes appear at nearly half the ideal geodesic acoustic mode frequency, in plasmas with comparable electron and ion temperatures and elevated magnetic safety factor (q_{min}>or=2). Strong bursting and frequency chirping are observed, concomitant with large (10%-15%) drops in the neutron emission. Large electron density fluctuations (n[over ]_{e}/n_{e} approximately 1.5%) are observed with no detectable electron temperature fluctuations, confirming a dominant compressional contribution to the pressure perturbation as predicted by kinetic theory. The observed mode frequency is consistent with a recent theoretical prediction for the energetic-particle-driven geodesic acoustic mode.

As part of the ITER Design Review, the physics requirements were reviewed and as appropriate updated. The focus of this paper will be on recent work affecting the ITER design with special emphasis on topics affecting near-term procurement arrangements. This paper will describe results on: design sensitivity studies, poloidal field coil requirements, vertical stability, effect of toroidal field ripple on thermal confinement, heat load requirements for plasma-facing components, edge localized modes control, resistive wall mode control, disruptions and disruption mitigation.

Utilizing a capability to vary neutral beam torque injection in the DIII-D ͓J. L. Luxon, Nucl. Fusion 42, 614 ͑2002͔͒ tokamak, m / n =2/ 1 neoclassical tearing mode onset thresholds are found to fall by about one unit in ␤ N , from ϳ3 to ϳ2, in ITER-like sawtoothing high-energy confinement modes of plasma operation ͓R. Aymar, Plasma Phys. Control. Fusion 42, B385 ͑2000͔͒ as "co-injected" torque and rotation are reduced. However, increasing levels of torque and rotation in the counter-direction do not lead to corresponding rises in ␤ N thresholds. More encouragingly, error field sensitivity is not found to increase in low rotation plasmas, as might be expected theoretically. These results pose an interesting physics problem, as well as raising concern for future devices such as ITER. Further analyses have explored possible physics origins of the behavior. They suggest many of the usual effects expected to lead to a rotation dependence ͑mode coupling, wall drag, ion polarization currents͒ are not significant, with instead models that depend on the size and sign of rotation shear playing a role. Onset behavior suggests the mode is close to being intrinsically ͑classically͒ unstable when it appears, and a conceptual explanation is offered for a mechanism by which rotation shear feeds into the onset process through changes to the classical tearing stability index, ⌬Ј. Further parameter extensions and studies are desirable to fully resolve the underlying physics of this interesting process.

͑2000͔͒ reveal the commonalities of resistive wall mode ͑RWM͒ stabilization by sufficiently fast toroidal plasma rotation in devices of different size and aspect ratio. In each device the weakly damped n = 1 RWM manifests itself by resonant field amplification ͑RFA͒ of externally applied n = 1 magnetic fields, which increases with the plasma pressure. Probing DIII-D and JET plasmas with similar ideal magnetohydrodynamic ͑MHD͒ stability properties with externally applied magnetic n = 1 fields, shows that the resulting RFA is independent of the machine size. In each device the drag resulting from RFA slows the toroidal plasma rotation and can lead to the onset of an unstable RWM. The critical plasma rotation required for stable operation in the plasma center decreases with increasing q 95 , which is explained by the inward shift of q surfaces where the critical rotation remains constant. The quantitative agreement of the critical rotation normalized to the inverse Alfvén time at the q = 2 surface in similar DIII-D and JET plasmas supports the independence of the RWM stabilization mechanism of machine size and indicates the importance of the q = 2 surface. At low aspect ratio the required fraction of the Alfvén velocity increases significantly. The ratio of the critical rotation in similar NSTX and DIII-D plasmas can be explained by trapped particles not contributing to the RWM stabilization, which is consistent with stabilization mechanisms that are based on ion Landau damping. Alternatively, the ratio of the required rotation to the sound wave velocity remains independent of aspect ratio.

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