Skip to main content

Energetic-particle-driven instabilities and induced fast-ion transport in a reversed field pinch

Type of Publication
Year of Publication
2014
Authors

L. Lin; J.K. Anderson; D.L. Brower; W. Capecchi; W.X. Ding; S. Eilerman; C.B. Forest; J.J. Koliner; D. Liu; M.D. Nornberg; J. Reusch; J.S. Sarff

Abstract

Multiple bursty energetic-particle (EP) driven modes with fishbone-like structure are observed during 1 MW tangential neutral-beam injection in a reversed field pinch (RFP) device. The distinguishing features of the RFP, including large magnetic shear (tending to add stability) and weak toroidal magnetic field (leading to stronger drive), provide a complementary environment to tokamak and stellarator configurations for exploring basic understanding of EP instabilities. Detailed measurements of the EP mode characteristics and temporal-spatial dynamics reveal their influence on fast ion transport. Density fluctuations exhibit a dynamically evolving, inboard-outboard asymmetric spatial structure that peaks in the core where fast ions reside. The measured mode frequencies are close to the computed shear Alfven frequency, a feature consistent with continuum modes destabilized by strong drive. The frequency pattern of the dominant mode depends on the fast-ion species. Multiple frequencies occur with deuterium fast ions compared to single frequency for hydrogen fast ions. Furthermore, as the safety factor (q) decreases, the toroidal mode number of the dominant EP mode transits from n = 5 to n = 6 while retaining the same poloidal mode number m = 1. The transition occurs when the m 1, n 5 wave-particle resonance condition cannot be satisfied as the fast-ion safety factor (q(fi)) decreases. The fast-ion temporal dynamics, measured by a neutral particle analyzer, resemble a classical predator-prey relaxation oscillation. It contains a slow-growth phase arising from the beam fueling followed by a rapid drop when the EP modes peak, indicating that the fluctuation-induced transport maintains a stiff fast-ion density profile. The inferred transport rate is strongly enhanced with the onset of multiple EP modes. (C) 2014 AIP Publishing LLC.

DOI

10.1063/1.4872029

Volume

21

Notes

Times Cited: 1 Lin, Liang/H-2255-2011; Eilerman, Scott/N-7831-2014 Eilerman, Scott/0000-0002-9048-0110 1

Number
5
ISSN Number

1070-664X

We are professional and reliable provider since we offer customers the most powerful and beautiful themes. Besides, we always catch the latest technology and adapt to follow world’s new trends to deliver the best themes to the market.

Contact info

We are the leaders in the building industries and factories. We're word wide. We never give up on the challenges.

Recent Posts