Runaway electrons with energies >100 keV are observed with the appearance of an m=1 magnetic island in the core of otherwise stochastic Madison Symmetric Torus [Dexter, Fusion Technol. 19, 131 (1991)] reversed-field-pinch plasmas. The island is associated with the innermost resonant tearing mode, which is usually the largest in the m=1 spectrum. The island appears over a range of mode spectra, from those with a weakly dominant mode to those, referred to as quasi single helicity, with a strongly dominant mode. In a stochastic field, the rate of electron loss increases with electron parallel velocity. Hence, high-energy electrons imply a region of reduced stochasticity. The global energy confinement time is about the same as in plasmas without high-energy electrons or an island in the core. Hence, the region of reduced stochasticity must be localized. Within a numerical reconstruction of the magnetic field topology, high-energy electrons are substantially better confined inside the island, relative to the external region. Therefore, it is deduced that the island provides a region of reduced stochasticity and that the high-energy electrons are generated and well confined within this region. © 2010 American Institute of Physics.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
Clayton, D. J., Chapman, B. E., O'Connell, R., Almagri, A. F., Burke, D. R., Forest, C. B., ... Piovesan, P. (2010). Observation of energetic electron confinement in a largely stochastic reversed-field pinch plasma. Physics of Plasmas, 17(1), -. . https://doi.org/10.1063/1.3292658