Study of a heating process of a hot plasma by Thomson scattering measurement

A multi-channel Thomson scattering measurement system was designed and constructed for the study of the heating process of hot plasma. The distribution of plasma density and the distribution of electron temperature were measured with this system. Plasma was produced with two theta pinch guns placed at the opposite sides. The plasma flows were led to the center of the apparatus by guide magnetic fields and collide, and made thermal. The apparatus was designed so as to make the magnetic compression heating of the colliding plasma with a main compression coil. A ruby laser system for the measurement was improved to raise the S/N ratio. A system of relay lenses and a multichannel prism array were constructed. The elimination of stray light was considered. The following results were obtained. The maximum density after the compression heating was about ten times as high as the initial density. There is some compression process in which the peak of the density propagates in radial direction. The ion temperature of the first step may be due to the thermalization of kinetic energy corresponding to this propagating speed. The density distribution preceding the magnetic piston was observed, which suggested the existence of the reflective ions. The same indication was also seen in the distribution of the electron temperature. Outgoing movement of the density peak was seen. The electron temperature was at most 300 eV. It is considered that the rapid ion heating of hot plasma may be caused by the reflective ions and the expansion process due to the outgoing movement of the reflective ions. (Kato, T.)