Evaluation of ultrasonic wave generation using electromagnetic acoustic transducer with current driven circuit

Characteristic of electromagnetism for a current driven electromagnetic acoustic transducer (EMAT) was estimated using numerical calculation method. High magnetic flux density above 2 T may be achieved by multi-layers piled up the conductors with 50 μm in thickness as a current circuit. This estimated value is much larger than that generated by the EMAT with the permanent magnets. The time variation of the current passing through the conductive layers depends on the characteristic impedance of the pulse forming network circuit. In the case of the larger value of the characteristic impedance compared with that of the internal resistance, the rectangular current was nearly obtained as a function of time. In contract, the current was exponentially decreased for the lower characteristic impedance. However, the time variation of the current supplied by the pulse forming network circuit may affect to only the value of the sound pressure at the detect point of ultrasonic wave. © 2011 The Institute of Electrical Engineers of Japan.