Neutral beam heating of a reversed-field pinch in the madison symmetric torus

Neutral beam injector (NBI) heating of electrons has been observed in the Madison Symmetric Torus (MST). This heating is consistent with a simple 1D model which includes the effect of fast ion diffusion, neutralizationlosses and classical collisional processes. This heating was achieved with a 1 MW NBI (25 kV, 40 A). Auxiliary heating of MST has been observed with Thomson scattering to be 100+/-50 eV in the core of 200 kA PPCD (pulsed poloidal current drive) plasmas. Auxiliary heating has been measured in other PPCD plasmas, but not in standard confinement plasmas. This data represents the first confirmed auxiliary heating of a reversed-field pinch (RFP) plasma. Enhanced confinement plasmas are conducive to auxiliary heating because of the improved thermal confinement.;Ion temperatures were measured with a Rutherford scattering device, but investigation deter- mined that NBI fast ions are able to get into the Rutherford analyzer at a large enough rate to add a significant non-Gaussian component to the observed data. Controlling for this additional neutral hydrogen signal eliminates false detection of auxiliary heating with NBI in standard MST plasmas. Further analysis suggests that fast ions from magnetic reconnection events could also be polluting MST sawtooth Rutherford data.;A 1-D model of NBI heating in MST was developed. This model takes measured and calculated inputs such as plasma temperature, plasma density and ohmic heating profiles and solves for heat diffusion coefficient profiles. The assumption underlying this calculation, that the heat diffusion coefficients do not change when the NBI is firing, is justified because the NBI does not significantly suppress mid-radius magnetic fluctuations.;The base 1-D model includes fast ion deposition, fast ion diffusion and fast ion slowing down. Fast ions are lost to the plasma via thermalization and contact with the MST wall. Neutral losses are added to the model using NENE, a Monte Carlo code. Finally, non-classical (resonant) fast ion diffusion is observed and modeled. This diffusion acts to limit core fast ion density, and appears as rapid bursts that occur approximately once or twice every millisecond.;The model output show that the 1-D classical model is consistent with measured DTe in PPCD plasmas. Fast ion diffusion is crucial in driving a flatter heating profile to limit heat conduction- losses. Measured core DTe is only possible with significant mid-radius heating.;Neutralization losses are modeled, which provide a loss mechanism for fast particles near the wall. Low core neutral densities in PPCD are crucial for the measured auxiliary heating. Neutralization losses are significant in standard plasmas, and explain the lack of significant DTe .;Finally, resonant diffusion is found not to have a significant effect on auxiliary heating of MST as long as a loss mechanism (neutralization) exists for fast ions near the MST wall.;The 1-D model demonstrates that auxiliary heating with NBI in PPCD can be modeled classically, where fast ion diffusion is a crucial physical process. Non-PPCD plasmas require a significant loss mechanism for fast ions near the MST wall, which can be provided by neutralization.