Multiphase flows are often opaque. This makes it hard to obtain experimental data to expand our knowledge about them. Even doing small scale experiments is hard, since most techniques that are used to investigate fluid flows use visible light. Therefore new techniques are being developed. One of them is Radioactive Particle Tracking using Single Photon Emission Computed Tomography, better known as SPECT. SPECT is already used for medical purposes, like locating tumors.
In this research we investigated with what accuracy a radioactive tracer particle, emitting gamma rays, can be tracked while moving in a stirred tank filled with 2.5 L of water. Therefore we did some experiments using a 2 mm polystyrene sphere with a golden core. The gold is activated in the reactor of the Reactor Institute Delft (RID) of the TU Delft, after which it will start to emit gamma rays. The gamma rays are detected by three gamma cameras placed around the tank. Each has a collimator with a cross slit in front of the detector plate, to obtain information about the location of the particle, such that by combining the information from the three detectors, its position can be reconstructed. First we did an experiment with a cobalt source, with a low activity, at multiple fixed positions in air, to test the setup. After that we did some experiments with the particle with gold, with a high activity, at multiple fixed positions in air,moving along a known circular trajectory in water and when moving freely in a stirred tank. The last two experiments are also carried out with the tank being aerated.
We found out that the inaccuracy in the reconstructions increases when: the tracer particle is positioned farther away from the center of the setup, the frame rate that is used is increased or the velocity of the tracer particle increases. The error ranges from 0.5 up to 4 mm depending on the settings. The injection of air
bubbles at the bottom of the tank with different air flow rates, did not seem to influence the accuracy. Although the accuracy is not that high, there are still a lot of improvements that can be made in order to increase the accuracy.