Spectroscopic investigation of Z-pinch with a spatial and temporal resolution

Soft X-rays generated by a plasma focus device with an Ar gas puff are stud ied using a composite system which consists of an imaging Bragg spectromete r and a soft X-ray high speed imaging system. Two modes of soft X-ray emitt ing sources in Z-pinch plasma, filamentary and scattered spots, are generat ed in this experiment depending on the delay time from the gas puff to the main discharge. Spectroscopic observation revealed that even the case of th e filamentary mode is not really filamentary but is actually X-ray emitting spots (hot spots) densely arranged in a column along the electrode axis. B y using the soft X-ray high speed imaging system, the streak mode display i s restructured from the data obtained in a single shot, Temporally resolved observations in streak mode showed that a spot appeared at a point near th e electrode face first, then different hot spots appeared successively alon g the axis and in a direction away from the electrode face. It is clarified that the hot spot is a small region from which intense H-like and He-like spectral lines are emitted. The size and the distance between spots are fro m 0.1 to 0.5 mm in radius and similar to 0.5 mm in length, respectively. Th e lifetime of the spots is 5 similar to 10 ns. The average electron tempera ture and density calculated from the intensity ratio of those spectral line s are similar to 1.8 keV and 1.7 x 10(22) /cm(3), respectively. They did no t show a notable change along the axis.