The Kinetic Stabilizer: A Route to Simpler Tandem Mirror Systems?
This paper discusses a new approach to an MHD stabilizing technique for magnetic fusion systems of the axisymmetric ''open-ended'' variety. The concept is adaptable to tandem-mirror systems and would result in a major simplification of such systems, accompanied by a substantial improvement in their confinement characteristics, The paper first discusses the present impetus to find a simpler and less expensive route to fusion than that offered by the mainline approach, the tokamak. The history of magnetic fusion research shows that closed and open systems exhibit very different confinement characteristics. Closed systems, such as the tokamak, the stellarator, or the reversed-field pinch have cross-field transport that is dominated by plasma turbulence. By contrast, there are examples of open-systems where turbulence, if present at all, was at such low levels that the transport agreed with ''classical'' predictions. The clearest examples are ones in which the field geometry was axiymmetric. However axisymmetric mirror systems are subject to MHD instability. Thus in the years following the famous Ioffe experiment, most open systems have employed asymmetric magnetic fields, with attendant problems of complexity and enhanced cross-field transport. This paper proposes a new means of stabilizing axisymmetric mirror-based systems. The idea, called the ''Kinetic Stabilizer'' has roots in experiments performed with the axisymmetric Gas Dynamic Trap at Novosibirsk. In these experiments, performed in a high collisionality plasma regime, it was shown that the presence of the effluent plasma in the positive-curvature expanding-field region outside the mirrors was effective in stabilizing a high-beta (30 percent) confined plasma against MHD modes. In the plasmas of tandem-mirror systems the density of the effluent plasma is too low to employ this method of stabilization. The Kinetic Stabilizer solves this problem by using ion beams, injected at small angles up the magnetic gradient outside the end mirrors, to create a localized stabilizing plasma by magnetic compression and reflection of the injected ions partway up the gradient. Theoretical analyses and code calculations are used to show that stability can be achieved even when the kinetic pressure of the Stabilizer plasma is many orders of magnitude lower than that of the confined plasma. It is estimated that axisymmetric tandem mirror systems producing hundreds of megawatts of fusion power could be stabilized using Stabilizer ion beams with a total power of order a few megawatts. If confirmed by further work, the Kinetic Stabilizer idea thus offers a much simpler approach to fusion power than the mainline approaches.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15007241
- Report Number(s):
- UCRL-JC-141533-REV-1; TRN: US0401487
- Resource Relation:
- Conference: 4th Symposium on Current Trends in International Fusion Research: A Review, Washington, DC (US), 03/12/2001--03/16/2001; Other Information: PBD: 30 May 2001
- Country of Publication:
- United States
- Language:
- English
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