|approved||epr_poster_bonofiglo_2017.pdf||2017-08-09 09:47:17||Phillip Bonofiglo|
Fast Ion Transport in the Three-Dimensional Reversed Field Pinch
Author: Phillip J Bonofiglo
Requested Type: Poster
Submitted: 2017-06-02 13:55:37
Co-authors: J. K. Anderson, E. Parke, M. Gobbin, J. Kim, J. Egedal
University of Wisconsin - Madison
1150 University Ave.
Madison, WI 53706
United States of Ame
A growing concern in fusion science is that of fast ion transport in three-dimensional magnetic topologies. In particular, reduction in plasma heating and confinement due to neoclassical and anomalous transport, such as that observed in stellarators, is an ever present problem. The reversed field pinch (RFP) provides a unique environment to study fast ion confinement and transport in both 2D and 3D geometries. In the axisymmetric RFP, guiding center drifts are along flux surfaces, resulting in naturally well-confined fast ions. At sufficiently high Lundquist number, the innermost tearing mode can grow and envelop the magnetic axis, creating a helical axis and 3D equilibrium. Experiments on the Madison Symmetric Torus (MST) reveal reduced confinement of fast ions with the transition to this quasi-single helicity (QSH) state. Current work aims to probe the dynamics of fast ion transport during QSH. Energetic particle modes (EPMs) upshift in frequency with growing core tearing mode amplitude and disappear in high plasma current QSH plasmas. Additionally, FIR interferometry has resolved electron density perturbations associated with EPMs. The FIR measurements show the upshifting EPMs moving radially outward as they grow in frequency, indicating transport associated with the transition to QSH. The Hamiltonian guiding center code ORBIT confirms rapid fast ion loss times in QSH and is being actively used to simulate diffusion coefficients and particle orbits for examining neoclassical transport. This research is supported by US DOE.