Shock Mitigation Using Compressible Two-Phase Jets for Z-Pinch IFE Applications

In a high-yield, low repetition rate Inertial Fusion Energy (IFE) system, such as the Z-Pinch IFE reactor, compressible liquid/gas jets offer the opportunity to protect the cavity walls from the target X-rays, ions and neutrons. They can especially limit and mitigate the mechanical consequences of the shock waves produced by rapid heating/evaporation of the protective jets. In this investigation, experiments have been conducted to examine the stability of two-phase jets and quantify the extent by which they can attenuate a shock wave. An exploding wire was used to generate a shock wave at the center of downward flowing annular single- and two-phase jets within a concentric cylindrical enclosure. The pressure history at the enclosure wall was recorded as the shock wave propagated through the attenuating two-phase medium. Experiments were conducted using two different-size jets and enclosures at various liquid velocities, void fractions, and initial shock strength. The data showed that stable coherent jets could be established and steadily maintained with relatively high void fractions and that significant attenuation in shock strength could be attained at relatively modest void fractions. The data obtained in this investigation can be used to validate predictions of shock attenuation models for future IFE reactor cavities.