Two-dimensional images of line integrated electron density for X-pinch plasmas using dark-field Schlieren and interferogram*

We present an interferogram analysis scheme for X-pinch plasmas which have current rising time of approximately 500 nsec. As X-pinch plasmas evolve in nano-second time scale, a short pulse width of ~150 psec laser beam (Nd:YAG, 532nm) is used as a light source of the imaging systems. Both the dark-field Schlieren with a ~600um-diameter solder ball and the Mach-Zehnder interferometer simultaneously image X-pinch plasmas with the pulsed laser beam. Since an interferogram analysis typically requires hand-tracing of dark fringes on the interferometer images, it is difficult to assess reliability of the hand-traced results unless they are compared with electron densities obtained by other independent diagnostic systems. As dark-field Schlieren image contains information about the gradient of line integrated electron density of X-pinch plasma, it can be qualitatively compared with the interferogram analysis results. The method of generating synthetic dark-field Schlieren images from the interferogram results is presented, and how it can support the interferogram analysis is discussed. Two-dimensional images of line integrated electron density for X-pinch plasmas using the proposed method are also presented.