Shock Mitigation Studies in Voided Liquids for Fusion Chamber Protection

A liquid pool, with and without void fractions, was subjected to dynamic compression testing in a vertical shock tube to model the bubbly-pool concept being considered for use in an inertial fusion energy reactor. Water and oil were used to model the FliBe coolant that collects at the bottom of the chamber and serves as first wall protection at that location. The experiments (shock strengths M = 1.4, 2.0, and 3.1) were conducted in atmospheric pressure argon, and argon was bubbled through the liquid to achieve void fractions of 5-15% in the 30.4 cm deep pool. Pressure measurements were taken in the pool at intervals of 2.54 cm to measure the effect of void fraction on the pool compression and the compression wave traveling through the liquid. The presence of the gas voids in the liquid had a strong effect on the dynamic pressure loading but did not reduce the shock impulse significantly at the low and intermediate Mach numbers, but did exhibit a mitigating effect at the higher shock strength. A very high void fraction foam was also studied that resulted in a 22% reduction of the shock wave impulse.