Witness foam-ball diagnostic for Nova hohlraum time-dependent drive asymmetry

1 January 1995

journal article
research article
Published by AIP Publishing in Review of Scientific Instruments

Vol. 66 (1) , 785-787
https://doi.org/10.1063/1.1146221

Abstract

Backlighting of low‐density SiO2 aerogel balls (0.3 g/cc) in Novahohlraums enables direct imaging of the indirectly driven ablative shock trajectory versus time. An immediate application of the technique is a new method for measuring drive temperature and asymmetry in Novahohlraums.Measured drive asymmetries are exaggerated due to an increased shock speed in low‐density foam balls. From the backlighter‐imaged distortion of the radially converging shock, a potentially useful time‐dependent flux asymmetry diagnostic is obtained. Results from a 3:1 peak‐to‐foot contrast ratio pulse shape (ps22) are analyzed and shown to agree with modeling. The current goal of the witness‐ball effort on Nova is to identify the transition in flux on capsule from waist high (sausaging) to pole high (pancaking), thereby validating the technique as a promising symmetry diagnostic for the proposed National Ignition Facility.

Keywords

This publication has 2 references indexed in Scilit:

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