Speaker
Dr
Alexei Beklemishev
(Budker Institute of Nuclear Physics)
Description
A new efficient method of confinement is proposed for use in linear traps. It is based on effect of diamagnetic expulsion of the magnetic field out of the plasma volume while beta tends to one. This effect is greater in the low-field area and weaker in mirrors, thus, if the plasma pressure grows, the equilibrium in a linear trap changes in such a way that the effective mirror ratio increases. As a result, the axial particle and energy confinement becomes gas-dynamic and improves linearly with diamagnetic expansion of the plasma bubble. This effect would enable construction of a compact fusion reactor, if one could ensure suppression of pressure-driven instabilities, in particular, the ballooning instability. This paper shows how it can be done: one should use magnetic configuration with a stretch of uniform field at its minimum, and place external stabilizers near ends of that stretch. The high-beta limit of plasma equilibrium in an open trap is shown to form a roughly cylindrical bubble around the stretch of uniform field with sharp non-paraxial ends. These ends are a sole source of ballooning instability, while their positioning and geometry make them also suitable for line-tying or feedback stabilization. Given that the external stabilizers and the instability source are close, the field flexibility at high beta can be ignored. Large Larmor radii of ions in the low-field bubble could ensure stability of short-wave modes, so that external boundary stabilizers should suffice. Fast-ion confinement, startup, and the energy balance issues are also considered for a linear trap in the diamagnetic-bubble regime.
This work has been supported by Russian Science Foundation (project N 14-50-00080)
Primary author
Dr
Alexei Beklemishev
(Budker Institute of Nuclear Physics)
