Radiation driven planar foil instability and mix experiments at the AWE HELEN laser

Abstract

This paper reviews recent developments and achievements in the program of planar foil instability experiments being performed at the AWE HELEN laser. Point projection Xray backlighting, with spectroscopy, is used to measure hydrodynamic mix in radiatively accelerated ablator/foil packages; the mix is identified in the experimental radiograph from the overlap of distinguishable spectral absorption features associated with each of the constituent materials. The first part of the paper describes the backlighting technique, and briefly summarizes progress made in the past two years, leading to the first results being obtained on a “high mix” Parylene-C ablator/molybdenum payload package. The second part considers the full analysis of one such ‘high mix’ shot (Shot 7772), describing how the spatial distribution of mix has been quantified and considering the various sources of error. Comparisons are made with both one-dimensional and two-dimensional hydrocode simulations. Finally, various improvements and extensions to the experiment and codes are indicated.