Abstract Details

files Add files

Reconstruction of current-driven equilibria in the Compact Toroidal Hybrid using magnetic diagnostics

Author: Benjamin A. Stevenson
Requested Type: Poster Only
Submitted: 2009-12-04 22:38:08

Co-authors: J. Hanson, G. Hartwell, J. Hebert, S. Knowlton

Contact Info:
Auburn University
1606 Ridge Rd
Opelika, AL   36801

Abstract Text:
An increasingly important part of improving the stability and confinement of fusion plasmas is a more thorough understanding of plasma equilibrium. There is a need for the capability of rapidly reconstructing fully three-dimensional equilibria in toroidal confinement experiments. Initial plasma reconstructions using the new V3FIT 3D magnetic equilibrium reconstruction code [1] will be presented using diagnostic data from the Compact Toroidal Hybrid (CTH). The CTH is a heliotron-type device in which the magnetic configuration can be strongly modified by an ohmically-driven plasma current. The operating parameters of CTH are R0 = 0.75 m, a ~ 0.2 m, B0 ≤ 0.7 T, ne = 0.2 – 1.5 x 1019 m-3, Te ~ 200 eV, Ip ≤ 40 kA, ivac(a) = 0.05 – 0.4. Currently signals from a set of magnetic diagnostics provide the experimental input to V3FIT which utilizes least-squares fitting and the VMEC equilibrium code [2] to reconstruct 3D plasma equilibria. The suite of magnetic diagnostics presently used includes internal and external segmented and full Rogowski coils, various flux loops, and a diamagnetic loop. The measured signals from these diagnostics include contributions from the plasma current, externally applied currents, vacuum vessel current, and various sources of pickup and drift. In order to properly reconstruct plasma equilibria, the model diagnostic response functions should closely match the actual diagnostic responses. In order to properly model the magnetic diagnostics, the mutual inductance of the external current sources with each diagnostic coil was experimentally determined. The induced toroidal vacuum vessel current (<15kA) significantly contributes to the magnetic diagnostic signals. In order to include this current contribution in the reconstruction process, the VALEN code [3] was used to model the time varying vacuum vessel current distribution.

Supported by US DOE Grant DE-FG02-00ER54610

[1] J. D. Hanson et al, Nucl. Fusion 49, 075031 (2009)
[2] S. P. Hirshman and D. K. Lee, Comput. Phys. Commun. 39, 161(1986)
[3] J. Bialek et al, Physics of Plasmas 8(5), 2170 (2001)

Characterization: A5,E1

I would request to be in the same poster session as the poster by Stephen Knowlton, also from Auburn University.

Princeton University

Innovative Confinement Concepts Workshop
February 16-19, 2010
Princeton, New Jersey

ICC 2010