Tokamak plasma variations under rapid compression
Changes in plasmas undergoing large, rapid compressions are examined numerically over the following range of aspect ratios A:3 greater than or equal to A greater than or equal to 1.5 for major radius compressions of circular, elliptical, and D-shaped cross sections; and 3 less than or equal to A less than or equal to 6 for minor radius compressions of circular and D-shaped cross sections. The numerical approach combines the computation of fixed boundary MHD equilibria with single-fluid, flux-surface-averaged energy balance, particle balance, and magnetic flux diffusion equations. It is found that the dependences of plasma current I/sub p/ and poloidal beta anti ..beta../sub p/ on the compression ratio C differ significantly in major radius compressions from those proposed by Furth and Yoshikawa. The present interpretation is that compression to small A dramatically increases the plasma current, which lowers anti ..beta../sub p/ and makes the plasma more paramagnetic. Despite large values of toroidal beta anti ..beta../sub T/ (greater than or equal to 30% with q/sub axis/ approx. = 1, q/sub edge/ approx. = 3), this tends to concentrate more toroidal flux near the magnetic axis, which means that a reduced minor radius is required to preserve the continuity of the toroidal flux function F at the plasma edge. Minor radius compressions to large aspect ratio agree well with the Furth-Yoshikawa scaling laws.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5640732
- Report Number(s):
- ORNL/TM-7227
- Country of Publication:
- United States
- Language:
- English
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