SUMMARY

Z-Pinch IFE (Inertial Fusion Energy) reactor designs will likely utilize high yield targets (~ 3 GJ) at low repetition rates (~ 0.1 Hz). Appropriately arranged thick liquid jets can protect the Z-Pinch IFE reactor cavity walls from the target X-rays, ions, and neutrons. However, the shock waves and the mechanical loadings produced by rapid heating and evaporation of incompressible liquid jets may be challenging to accommodate within a small reactor cavity. This investigation examines the possibility of using compressible, two-phase, liquid/gas jets as a means of limiting and mitigating the mechanical consequences of rapid energy deposition within the jets in a high-yield, low repetition rate, Z-Pinch IFE reactor system. Experiments have been conducted to examine the effect of void fraction and nozzle design on the stability and behavior of a two-phase jet discharging into an open cavity. Planar, circular, and annular jets have been examined over wide ranges of liquid velocities and void fractions. An exploding wire has been 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 has been recorded as the shock wave propagates through the attenuating two-phase medium. Experiments have been conducted using two different-size jets and enclosures at various liquid velocities, void fractions, and initial shock strength. The data show that stable coherent jets can be established and steadily maintained with relatively high void fractions and that significant attenuation in shock strength can be attained at relatively modest void fractions. Experiments will be conducted to measure the actual void fractions and slip ratios at different locations within the discharging jet. The data will be compared against predictions of a mechanistic two-fluid model; the model can be used to quantify the wall-protection-effectiveness of the two-phase jets.