Y.-K. M. Peng,**
Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08543
E. T. Cheng,
TSI Research Inc., 225 Stevens Ave., Solana Beach, CA 92075
J. G. Galambos, D. J. Strickler,
Oak Ridge National Laboratory, P.O. Box 2009, Oak Ridge, TN 37831
S. E. Berk,
U.S. Department of Energy, Germantown, MD 20874
Physics and systems design analyses are carried out to estimate the desired core parameters for a Spherical Torus (ST) based VNS that utilizes a single-turn toroidal field coil (TFC). To ensure a nearer-term reliable test environment for fusion power technologies, such a VNS must:
1) Have a plasma that operates in a parameter space removed from the physics and engineering limits while producing adequate performance (neutron wall loading WL = 0.5-2 MW/m2);
2) Configure the fusion core components: center leg of TFC, first wall, divertors, breeding shields, test blanket modules, and plasma drive systems, for full remote replacement.
3) Require only modest performance (WL = 0.5MW/m2) for the initial test program, determined by the available capabilities of these components, such as those being developed for ITER. The capabilities of these components will be tested, developed, and upgraded together with the plasma performance of the VNS facility.
Proof-of-principle tests of the ST plasma, such as NSTX (U.S.), MAST (U.K.), and GLOBUS-M (R.F.) presently under construction, are expected to provide much of the deuterium plasma physics database needed for the design of such a VNS. Upgrade of these tests to driven, D-T-fueled burn experiments is expected to provide the database needed to begin VNS operation.
Assuming successful outcome of these physics tests, a desired VNS fusion core is estimated to have major radius R0 = 1.07m, aspect ratio = 1.4, and toroidal field Bt0 = 2.7T at R0. At full performance the fusion plasma would assume elongation k = 3, plasma current Ip = 14MA, safety factor q0 = 10, average toroidal beta b< 40%, and bootstrap current fraction fbs = 90%. Such plasma could ultimately produce WL = 5MW/m2 and fusion power = 400MW, given neutral beam or rf drive power Pdrive = 70MW and core components capable for such performance.
However, to achieve reliable initial operation of the VNS fusion core, ITER-like core components would be utilized. The initial VNS core should only produce WL = 0.5MW/m2 and retain large margins within the physics and engineering operational limits. Such operation would then require only k < 2.3 to ensure intrinsic vertical stability; Ip = 8MA, q0 = 7; b < 25%; fbs < 60%; fusion amplification = 1; naturally diverted scrape-off layer with large flux tube expansion; Bt0 = 2T; Pdrive = 40MW; etc. Detail will be presented.
* Work supported by U.S. Department of Energy, Small Business Innovative Research Grant No. DE-FG03-95ER82098.
** On assignment from Oak Ridge National Laboratory, P.O. Box 2009, Oak Ridge, TN 37831