We performed spatially and temporally resolved Thomson scatteringin a plasma generated in a gas-liner z-pinch, where the amount ofaxially distributed impurity ions seeded in a hydrogen plasma canbe controlled. The parameters of the plasma electron density,temperature, concentration of impurity ions as well as the bulkvelocity of the plasma are measured along both the radius and thez-axis. The temporal behaviour is studied from shot to shot.Depending on the impurity concentration on the axis and the kindof impurities, the homogeneity and stability of the plasmacolumn along the z-axis are investigated. For small impurityconcentrations the impurity ions are located in the homogeneouscentral part of the plasma offering excellent conditions to testtheories on Stark broadening of spectral lines. Modulations of thedensity and temperature along the axis start to rise when theconcentration of the impurity ions exceed a certain limitdepending on their charge number. The modulations are related toRayleigh-Taylor instabilities growing during the late phase of thecompression.
Observation of the bulk ion density peaking in a discharge with an impurity hole in the LHD