Indexed on: 23 Dec '06Published on: 23 Dec '06Published in: Journal of Fusion Energy
Coaxial plasma guns are commonly used to inject magnetic helicity in innovative confinement concepts (ICC’s) for magnetic fusion. One of the key issues in magnetic helicity injection is to maximize the magnetic helicity injection rate. We have identified experimentally an alternative way to increase the magnetic helicity injection rate through rotating plasmas by extending the length of the inner electrode of a coaxial plasma gun so that an additional E × B region interweaves the standard J//B configuration. In the so-called “enhanced helicity injection” mode, the gun voltage is larger compared with the “normal” mode and decays more slowly. Another signature of the enhanced mode is increased edge magnetic field in conjunction with larger edge rotation. The results indicate that tuning plasma rotation is another way to enhance magnetic helicity injection using coaxial plasma guns. An alternative ICC is proposed based on the experimental observations.