Fluorescence and interferometry measurements for determining the r, z density distribution in a gas-puff z-pinch load

Two systems were developed for measuring the time-dependent 3D density distribution of a cylindrical gas jet injected into vacuum through a triple valve-nozzle system: i) planar-laser-induced-fluorescence (PLIF), where the density distribution in either the r-z or the r-thetas planes is obtained with sub-millimeter resolution in a single measurement; ii) chordal interferometry, where Abel inversion of the data gives the radial density distribution. The use of the two methods simultaneously turned out to be important for substantiating the measurement reliability, and for obtaining an absolute calibration for the PLIF method. The measurement accuracy was improved and assessed. The PLIF resolution allows for detecting density peaks of 1 mm width. Effects of a slight misalignment of the nozzle system were seen by detecting a few % azimuthal asymmetry. The measurements also allowed for determining the boundary-layer thickness at the nozzle exit plane. The lowest density that could be detected is of the order of 10¹⁶ cm^-3, however progress is made in measuring lower densities. The various findings can be used to examine hydrodynamics modeling of the gas flow in and outside the nozzle system.