A review on velocity measurements in liquid metals

For an MRI experiment with some liquid metal the possibilities for velocity measurements should be taken into account from the beginning. We present a summary of such measuring techniques, mainly focussing on local potential probes and the ultrasonic Doppler velocimetry. The latter is especially attractive as it provides a full velocity profile along the ultrasonic beam. The possibility of a full 3D velocity tomography, recently shown in a demo experiment, will also be discussed.