Importance of plasma response to nonaxisymmetric perturbations in tokamaks
- Princeton Plasma Physics Laboratory, Princeton, New Jersey, New Jersey 08543 (United States)
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)
- General Atomics, San Diego, California 92186 (United States)
Tokamaks are sensitive to deviations from axisymmetry as small as {delta}B/B{sub 0}{approx}10{sup -4}. These nonaxisymmetric perturbations greatly modify plasma confinement and performance by either destroying magnetic surfaces with subsequent locking or deforming magnetic surfaces with associated nonambipolar transport. The Ideal Perturbed Equilibrium Code (IPEC) calculates ideal perturbed equilibria and provides important basis for understanding the sensitivity of tokamak plasmas to perturbations. IPEC calculations indicate that the ideal plasma response, or equivalently the effect by ideally perturbed plasma currents, is essential to explain locking experiments on National Spherical Torus eXperiment (NSTX) and DIII-D. The ideal plasma response is also important for neoclassical toroidal viscosity (NTV) in nonambipolar transport. The consistency between NTV theory and magnetic braking experiments on NSTX and DIII-D can be improved when the variation in the field strength in IPEC is coupled with generalized NTV theory. These plasma response effects will be compared with the previous vacuum superpositions to illustrate the importance. However, plasma response based on ideal perturbed equilibria is still not sufficiently accurate to predict the details of NTV transport and can be inconsistent when currents associated with a toroidal torque become comparable to ideal perturbed currents.
- OSTI ID:
- 21277166
- Journal Information:
- Physics of Plasmas, Vol. 16, Issue 5; Other Information: DOI: 10.1063/1.3122862; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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