Applying Forward Modeling to Compare Asay Foils and Windows in Support of Shallow Bubble Collapse Mechanism

Asay diagnostics have been prominently used for measuring ejecta momentum since being introduced by Asay et al. Such diagnostics typically utilizes an opaque foil of known mass. As ejecta are deposited on the foil surface, velocimetry measurements from the foil back surface are used to infer the momentum deposition and calculate the ejecta mass distribution. A transparent Asay window can be used in place of the opaque foil to allow for velocimetry measurements closer to the location of ejecta deposition. In the present work, cerium ejecta experiments are performed with both Asay foils and windows. These experimental diagnostics are forward modelled numerically using high-resolution hydrodynamic simulations for the cerium ejecta impacting the Asay windows and foils. For high momentum deposition rates, we found that the perturbations from individual ejecta coalesce into shocks, resulting in degenerate solutions of the ejecta mass distribution. By using an Asay window with an embedded mirror, the perturbations from the individual ejecta have less distance/time to coalesce before being measured via velocimetry. The talk will highlight the utility of forward models to identify the failure conditions of Asay foils and the uncertainty reduction of the corresponding Asay windows.