Abstract
A sensitive interferometer [B. V. Weber and S. F. Fulghum, Rev. Sci. Instrum. 68, 1227 (1997)] with 10−5-wave phase resolution is used to measure gas distributions from axisymmetric, supersonic nozzles employed in high power Z-pinch experiments. The line-integrated gas density, N≡∫ndx, is measured as a function of time at one distance, z, from the nozzle and one distance, y, from the axis. The (y,z) region of interest is scanned shot to shot. The N(y) data are analyzed to find radial density distributions via Abel inversion: n(r)=−(1/π)∫r∞[(dN/dy)/y2−r2]dy. Error propagation based on the uncertainty in N results in larger relative uncertainties in n, especially near the axis. The precision may be improved using a modified version of this interferometer, where the reference beam is moved into the gas, a small distance (1–2 mm) from the scene beam. The phase difference is then a direct measurement of dN/dy, reducing the error introduced by numerically differentiating N. These two techniques are compared using two nozzles with different density distributions from DECADE Module 2 Z-pinch experiments.
Published Version
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