Shock velocity measurement inside high density polyethylene using mid-infrared photonic Doppler velocimetry

Measuring shockwave velocity within a material is often beyond the capability of conventional photonic Doppler velocimetry (PDV) due to material opacity. This paper presents an experimental demonstration of shockwave measurement within high density polyethylene (HDPE) using a free-space photonic Doppler velocimeter operating in the 9–11 μm range (mid-infrared, Mid-IR). The shockwave is generated in HDPE by running a plate impact experiment with a gas launcher, inducing a refractive index change at the wave interface within the HDPE, and enabling partial reflection of the beam. The Mid-IR system is connected to the target by a hollow core fiber, which captures the reflected Mid-IR signal for velocity measurement. We measure the shock velocity within HDPE at 2600 m/s and record the beginning of particle velocity through the shocked HDPE near 500 m/s. A numerical simulation with OURANOS hydrocode shows good agreement with experimental results, despite edge effects and unperfected equation of state. These results confirm that Mid-IR PDV is an ideal candidate for material characterization under more extreme conditions such as detonation in energetic materials.