Observation of energetic electron confinement in a largely stochastic reversed-field pinch plasma

D.J. Clayton, B.E. Chapman, R. O'Connell, A.F. Almagri, D.R. Burke, C.B. Forest, J.A. Goetz, M.C. Kaufman, F. Bonomo, P. Franz, M. Gobbin, P. Piovesan

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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.
Original languageEnglish
Article number012505
Pages (from-to)-
JournalPhysics of Plasmas
Issue number1
Publication statusPublished - 2010
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Cite this

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), -. [012505]. https://doi.org/10.1063/1.3292658