Return To: Session TH/P2 - Stability and Divertors
Prev Page: Session TH/P2 - Stability and Divertors
Next Page: (TH/P2-02) Effect of Beta and Collisionality on the

(TH/P2-01) Theoretical Investigation of Field-Line Quality in a Driven Spheromak

R.H. Cohen¹⁾, H.L. Berk²⁾, B.I. Cohen¹⁾, T.K. Fowler³⁾, A.H. Glasser⁴⁾, E.B. Hooper¹⁾, L.L. LoDestro¹⁾, E.C. Morse³⁾, L.D. Pearlstein¹⁾, T.D. Rognlien¹⁾, D.D. Ryutov¹⁾, C.R. Sovinec⁵⁾, S. Woodruff^1)
 
1) Lawrence Livermore National Laboratory, Livermore, CA, USA
²⁾ Institute for Fusion Studies, University of Texas, Austin, TX, USA
³⁾ Department of Nuclear Engineering, University of California, Berkeley, CA, USA
⁴⁾ Los Alamos National Laboratory, Los Alamos, NM, USA
⁵⁾ University of Wisconsin, Madison WI 53706 USA

Abstract.  The ability of a spheromak to confine heat while current is injected to balance Ohmic dissipation depends on the quality of the magnetic field lines. We describe several approaches to prediction and assessment of field-line quality. Nonlinear resistive-MHD simulations are performed with NIMROD and a Galerkin code. NIMROD results for the SSPX Experiment agree semi-quantitatively on many features, and show strongly driven spheromaks to have stochastic field lines; field-line quality is improved with weak drive, bias coils, or cyclic operation. Mercier analysis of SSPX indicates operation near marginal stability. DCON stability comparisons are also shown. The Connor-Taylor scaling analysis of confinement in stochastic fields of an RFP has been repeated for a spheromak equilibrium. A calculation of current diffusion in a magnetic field tangled by tearing modes is presented, as are results for flux amplification from a free-boundary MHD equilibrium calculation with hyper-resistivity. The consequences of strictly parallel transport are explored, and points of contact with experimental results found. A theory is presented for the use of hot electrons as a probe of field-line quality.

Read the full paper in PDF format.