Pulse-Echo Ultrasound in DC Fields

When a burst of an rf signal is applied to the transmitter, the latter generates an ultrasound pulse with the same duration. This ultrasound pulse propagates across the sample and, when it arrives at the receiver transducer, generates an rf pulse. The ultrasound pulse propagates back and forth and creates additional rf pulses at the receiver—a so called “echo train.” The sound propagation time is determined by the sound velocity and hence by the associated elastic constant. The time evolution of the amplitude of the received pulse is defined by the sound attenuation. Both the ultrasound velocity and attenuation are intrinsic properties of the material and can be changed only by varying some external parameters such as temperature, magnetic field or pressure, for example. Investigation of a relative change of the velocity and attenuation on these external parameters is implemented at the MagLab.