PEPT combined with high speed digital imaging for particle tracking in dynamic foams

Positron emission particle tracking (PEPT) has been combined with high speed digital imaging to track a particle within a foam column. The tracer was sufficiently large (diameter 2.5 mm) to allow visual verification of the tracer trajectory recorded with PEPT. This enables validation of the technique for use with smaller, less visible, tracers in the future. A difference in recording rates of PEPT and the high speed camera necessitated the use of a weighting function to interpolate the discrete PEPT data set into a continuous function. A kernel width of 200 ms was used to ensure a confidence level of 95% that the tracer position calculated from PEPT and measured visually were the same, within error limits of ±2.7 mm. The largest contribution to the error was the resolution of the images. Images of dynamic foam structure can now be paired with PEPT measurement to observe the tracer trajectory relative to individual bubbles.