Magnetic compression heating of extremely high beta plasma configuration

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Plasma with field-reversed configuration has extremely high beta value (plasma pressure/ confining magnetic field pressure) of about 1. Therefore, confining magnetic field of the FRC fusion reactor can be far weaker than in low beta confinement schemes, which is favorable for technological viewpoint. High-energy neutral beam (NB) is the most important method to heat and sustain the FRC plasma. As the cost of the NB is expensive, it is desired that the FRC plasma should have good confinement property to reduce the cost of the NB. It is known that confinement time of the FRC plasma is proportional to 2-3 powers of the radius r_s of the FRC plasma. Up to present, r_s has increased by translating the plasma from formation region to confinement region. This technology of translation has an advantage that r_s can be increased without serious lowering of plasma temperature. But it has a disadvantage that obtainable value of r_s is limited: By the translation, the FRC plasma is ejected into th … More e confinement region with supersonic velocity and it must be stopped, when the plasma expands radially, excessively and the confinement is degraded because, perhaps, the plasma touches the wall. In order to increase r_s, new scheme of axial compression is proposed. The FRC plasma is compressed radially by decreasing the distance between the mirror fields, which are confining the plasma. Coils were developed to realize this compression, which coils produced magnetic field with the rise time of about 50μs, which is faster than confinement times and slower than propagation of sound wave. These coils were installed in the vacuum chamber and were energized successively. The result of the compression could be explained by adiabatic theory when the effect of energy loss and the magnetic flux loss were token into account. Moreover, it was also observed that the confinement property did not depend on the plasma length even when the plasma was compressed until the elongation (plasma length / plasma radius) or the aspect ratio became as small as 4.1. Less