Investigation Of Plasma Discharges Within Maja-PF Device Operated With Tungsten Inserts In The Central Electrode

摘要

The paper presents results of recent experimental studies with a MAJA-PF plasma-focus facility, as carried out for two different configurations of the end-plate of the central electrode. The main aim was to investigate an influence of the shape and material of the electrode end-plate on the formation and structure of the plasma column as well as to record and identify spectral lines of tungsten. The first version of the end-plate was made of Cu, while the second one had an insert made of a Cu-W alloy. Optical spectra were recorded by means of a Mechelle?900 spectrometer, operated with some delay in relation to a current peculiarity and with exposition times varied from 200 ns to 10 μs. For shots with the Cu electrode spectral lines of deuterium (working gas) and carbon ions were recorded, but tungsten lines were not identified. It was estimated that the electron concentration changed from (8÷10)×1017 cm?3 to about 2×1017 cm_3 in 5 μs after the current dip. In experiments with the second electrode version, among numerous spectral lines there were identified distinct WI and WII lines. Estimates of the tungsten ion concentration were impossible because of close positions of other lines. Diagrams of changes in the electron density are of importance for applications of DPM streams.