Review of x-ray polarization measurements on z-pinches in Russia and Poland

This paper describes overviews on the experimental results of the He-like lines of iron and argon emitted from vacuum spark plasmas (150 kA) from the standpoint of polarization study. This paper includes also the plasma focus at the discharge current 500 kA and the Z-pinch with the current of 3 MA (ANGARA- 5- 1), which is discussed for the first time here. Typical examples are obtained on the MHD calculations for the argon discharge, which include the magnetic field pressure, the plasma outflow in the z-direction, anomalous Joule heating, radiation losses and the generation of an electron beam. It is noted that difficulties in doing a more complete analysis on polarization are partly experimental. It would be desirable if we can have a crystal, which gives lower order reflection angle that coincides with the Brewster angle for X-ray. Careful quantitative interpretation of polarization phenomena in hot dense plasmas need a theory that takes into account important details of the processes involved. The theoretical predictions by the time dependent collisional-radiative model indicate generation of fast electrons and atomic rates integrated over a non-Maxwellian distribution function, the opacity effect, the cascade feeding, the fine structures of appropriate levels, generation of high electromagnetic fields and their influence on energy level, including forbidden line, etc. A more satisfactory and quantitative interpretation of the results presented here is underway. (Tanaka, Y.)