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Leading resistive wall mode (RWM) stability codes MARS-K [Liu et al., Phys. Plasmas 15, 112503 (2008)] and MISK [Hu et al., Phys. Plasmas 12, 057301 (2005)] have been previously benchmarked. The benchmarking has now been extended to include additional physics and used to project the stability of ITER in a realistic operating space. Due to ITER's relatively low plasma rotation and collisionality, collisions and non-resonance rotational effects were both found to have little impact on stability and these non-resonance rotational effects will also not self-consistently affect the ITER RWM eigenfunction. Resonances between thermal ions and electrons and the expected level of ITER toroidal rotation were found to be important to stability, as were alpha particles, which are not in rotational resonance. MISK calculations show that without alpha particles, ITER is projected to be unstable to the RWM, but the expected level of alphas is calculated to provide a sufficient level of stability. [ABSTRACT FROM AUTHOR]

Stability of a special class of the infernal mode, i.e., the one which is localized near the plasma edge, is numerically investigated for a toroidal plasma, using the single fluid code MARS-F [Liu et al., Phys. Plasmas 7, 3681 (2000)] and magneto-hydrodynamic-kinetic hybrid code MARS-K [Liu et al., Phys. Plasmas 15, 112503 (2008)]. Unlike the peeling-ballooning instabilities, which are thought to be responsible for the onset of type-I edge localized modes, the edge localized infernal mode may be responsible for accessing certain quiescent H-mode regimes in tokamak discharges. The finite plasma pressure near the plasma edge drives this instability. The local flattening of the safety factor near a rational surface at the plasma edge region, due to the large bootstrap current contribution in H-mode plasmas, is a necessary condition for the mode instability. It is found that the plasma toroidal flow shear in the pedestal region, as well as the plasma resistivity, further destabilizes the edge localized infernal mode. The drift kinetic effects from thermal particles, on the other hand, partially stabilize the mode. The flow shear and the drift kinetic effects also modify the symmetry of the mode spectrum, by enlarging the unstable domain towards higher local qmin value. No substantial modification of the mode eigen-structure is observed by the plasma flow, resistivity, or the kinetic effects. These results can be relevant to understanding physics of certain quiescent H-mode regimes. [ABSTRACT FROM AUTHOR]

A quantitative interpretation of the experimentally measured high-pressure plasma response to externally applied three-dimensional (3D) magnetic field perturbations, across the no-wall Troyon β limit, is achieved. The self-consistent inclusion of the drift kinetic effects in magnetohydrodynamic (MHD) modeling [Y. Q. Liu etal., Phys. Plasmas 15, 112503 (2008)] successfully resolves an outstanding issue of the ideal MHD model, which significantly overpredicts the plasma-induced field amplification near the no-wall limit, as compared to experiments. The model leads to quantitative agreement not only for the measured field amplitude and toroidal phase but also for the measured internal 3D displacement of the plasma. The results can be important to the prediction of the reliable plasma behavior in advanced fusion devices, such as ITER [K. Ikeda, Nucl. Fusion 47, SI (2007)]. [ABSTRACT FROM AUTHOR]

Validating the calculations of kinetic resistive wall mode (RWM) stability is important for confidently predicting RWM stable operating regions in ITER and other high performance tokamaks for disruption avoidance. Benchmarking the calculations of the Magnetohydrodynamic Resistive Spectrum-Kinetic (MARS-K) [Y. Liu et al., Phys. Plasmas 15, 112503 (2008)], Modification to Ideal Stability by Kinetic effects (MISK) [B. Hu et al., Phys. Plasmas 12, 057301 (2005)], and Perturbed Equilibrium Nonambipolar Transport (PENT) [N. Logan et al., Phys. Plasmas 20, 122507 (2013)] codes for two Solov'ev analytical equilibria and a projected ITER equilibrium has demonstrated good agreement between the codes. The important particle frequencies, the frequency resonance energy integral in which they are used, the marginally stable eigenfunctions, perturbed Lagrangians, and fluid growth rates are all generally consistent between the codes. The most important kinetic effect at low rotation is the resonance between the mode rotation and the trapped thermal particle's precession drift, and MARS-K, MISK, and PENT show good agreement in this term. The different ways the rational surface contribution was treated historically in the codes is identified as a source of disagreement in the bounce and transit resonance terms at higher plasma rotation. Calculations from all of the codes support the present understanding that RWM stability can be increased by kinetic effects at low rotation through precession drift resonance and at high rotation by bounce and transit resonances, while intermediate rotation can remain susceptible to instability. The applicability of benchmarked kinetic stability calculations to experimental results is demonstrated by the prediction of MISK calculations of near marginal growth rates for experimental marginal stability points from the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)]. [ABSTRACT FROM AUTHOR]

The kinetic effects of thermal particles on the resistive wall mode (RWM) are studied in reversed field pinch (RFP) by adopting the toroidal hybrid stability code MARS-K (Liu et al 2008 Phys. Plasmas 15 112503) where the drift kinetic effects are included self-consistently. It is found that the transit ion resonance can provide ion acoustic Landau damping to stabilize the RWMs in high-beta plasmas. The trapped particles do not play a significant role in kinetic stabilization. The required critical flow rotation frequency is in the ion acoustic range which is much smaller than that predicted previously by fluid theory (Guo et al 1999 Phys. Plasmas 6 3868). The most unstable mode, having its rational surface closest to the plasma, can be stabilized for the wall near the plasma (e.g. n = 6 mode in RFX-mod) with the flow rotation in a few per cent of the Alfvén frequency. For other RWMs with different toroidal wave numbers n the stabilization conditions depend on the wall position and plasma βp. An analysis based on the potential energy components is carried out for physical understanding. The preliminary study on the effects of collisionality is also presented. [ABSTRACT FROM AUTHOR]

A cylindrical magnetohydrodynamic model including plasma pressure and longitudinal flow has been employed for the study of resistive wall mode (RWM) in reversed field pinch (RFP) plasmas. In order to validate the model, a careful comparison with the experimental measurements in RFX-mod [P. Sonato et al., Fusion Eng. Des. 66–68, 161 (2003)] on the mode growth rates has been made by well matching the equilibrium parameters F, Θ, and βp. The RWM instability spectrum, which varies with the equilibrium parameters, is also calculated for comparison. The sensitivity of the mode growth rate to the equilibrium parameters is studied in details. It is concluded that the model can provide consistent accuracy in studies of RWM in RFP plasmas. The analysis based on the balance of the potential energy components has been carried out in order to obtain the physical understanding on the mode behavior. [ABSTRACT FROM AUTHOR]