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hudson_icc_2007_for_upload.pdf2007-04-03 13:16:35Ben Hudson

Confinement Studies in High Temperature Spheromak Plasmas

Author: Ben Hudson
Requested Type: Poster Only
Submitted: 2006-12-18 21:33:33

Co-authors: H.S. McLean, T.A. Casper, E.B. Hooper, J. Jayakumar, L.L. LoDestro, L.D. Pearlstein, C. Romero-Talamas, R.D. Wood

Contact Info:
Lawrence Livermore National Laboratory
PO Box 808
Livermore, CA   94550

Abstract Text:
Recent results from the SSPX spheromak experiment demonstrate the potential for obtaining good energy confinement (Te > 350eV and radial electron thermal diffusivity comparable to tokamak L-mode values) in a self-organized toroidal plasma. Energy confinement and transport data in ohmically-heated SSPX discharges are compared against several transport models applicable to self-organized systems maintained by DC helicity injection. A strong decrease in thermal conductivity with temperature is observed and at the highest temperatures, transport is well below that expected from the Rechester-Rosenbluth model. Recent improvements to performance result from increasing both gun flux and current to increase the magnetic field while keeping a relatively flat current profile to minimize magnetic fluctuations. At temperatures above 300eV, it becomes possible to use modest (1 MW) amounts of neutral beam injection (NBI) auxiliary heating to significantly change the power balance in the core plasma, making it an effective tool for improving transport analysis. We are now developing detailed designs for adding NBI to SSPX and have developed a new module for the CORSICA transport code to compute the correct fast-ion orbits in SSPX. This module, coupled to a deposition code (NFREYA), is used to calculate the particle, current and power deposition from NBI. Initial CORSICA results show that a substantial fraction of the injected bean, of order 70%, is confined as fast ions, which is sufficient to raise the electron temperature and total plasma pressure in the core by a factor of two. Large changes in heating efficiency are observed in the modeling as the injection angle is varied, with tangential injection better than normal injection. CORSICA shows appreciable current driven on axis during tangential injection NBI suggesting the possibility of steady-state current drive without dynamo-driven fluctuations.

* Work performed under the auspices of the US DOE by University of California Lawrence Livermore National Laboratory under contract W–7405–ENG–48.

Characterization: A1,E3

group according to instructions McLean abstract submission.

University of Maryland

Innovative Confinement Concepts Workshop
February 12-14, 2007
College Park, Maryland

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