Magnetic compression heating of extremely high beta plasma configuration

反向场结构的等离子体具有极高的β值(等离子体压力/约束磁场压力)，约为1。因此，FRC聚变反应堆的约束磁场可以远远弱于低β约束方案，这对技术观点是有利的。高能中性束是加热和维持FRC等离子体的最重要的手段。由于NB的成本很高，因此希望FRC等离子体具有良好的约束性能，以降低NB的成本。已知FRC等离子体的约束时间与FRC等离子体半径r_S的2-3次方成正比。到目前为止，r_S是通过将等离子体从生成区转移到禁闭区而增大的。这种平移技术的优点是，可以在不严重降低等离子体温度的情况下提高r_S。但它的缺点是r_S的可获得值是有限的：通过平移，纤维混凝土等离子体被喷射到…中更多超音速的禁闭区域，当等离子体径向过度膨胀，约束退化时，必须停止这种禁闭，这可能是因为等离子体接触了壁面。为了提高r_S，提出了轴向压缩的新方案。通过减小限制等离子体的镜像场之间的距离，FRC等离子体被径向压缩。为了实现这种压缩，研制了线圈，线圈产生的磁场上升时间约为50μ，S比禁闭时间快，但比声波传播慢。这些线圈安装在真空室中，并相继通电。当考虑能量损失和磁通损失时，压缩的结果可以用绝热理论来解释。此外，还观察到，即使当等离子体被压缩到伸长率(等离子体长度/等离子体半径)或长宽比减小到4.1时，约束性质也不依赖于等离子体长度。较少

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